tag:blogger.com,1999:blog-62079996615861718742024-03-18T15:44:31.531-04:00Pattern and Match by VE3VNRon Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.comBlogger588125tag:blogger.com,1999:blog-6207999661586171874.post-20580411593973311562024-03-07T14:33:00.000-05:002024-03-07T14:35:20.399-05:00Interlude<p>As happens to all of us from time to time, I am currently dealing with a serious family matter. My usual pace of blogging will have to be reduced for the rest of March. What articles I write may be "lightweight" since my operating and station building activities are at a standstill. The previous article only got published because it was 95% complete and the final 5% served as a welcome distraction. </p><p>I had to cancel my plan for the ARRL DX SSB contest. Upcoming contests will also be sidelined until at least CQ WPX SSB in late March.</p><p>On the positive side, this unfortunate event has given me an opportunity to peruse old photo albums that were kept by a deceased family member. It goes back more than 100 years, following my family from its roots in Romania, to my parents' move to the Canadian prairie, and eventually to my arrival into the world. I knew that somewhere among those dusty albums was a picture I had long since lost track of. It brings back pleasant memories and may be of interest to readers. The picture was taken by my father.<br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhilO77xqj_Wh63Zwsinm216GbC3kfD6SZqdXtAcwrCyCQf_epn-PnD8jQolwJMQabM0WVTv7TK2vnrKFpJoQEa7GxN1c7X3D0J7pptqDO6ljo8ZZUwrNHywgh5zEY4NLTHbI0GTpOfGtJUpBLvblz_m20YkZ_1ETI7hIiPLjf_PzuyqO8XkzUUEjNZd_gx/s801/ve4oy_1972.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="801" data-original-width="800" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhilO77xqj_Wh63Zwsinm216GbC3kfD6SZqdXtAcwrCyCQf_epn-PnD8jQolwJMQabM0WVTv7TK2vnrKFpJoQEa7GxN1c7X3D0J7pptqDO6ljo8ZZUwrNHywgh5zEY4NLTHbI0GTpOfGtJUpBLvblz_m20YkZ_1ETI7hIiPLjf_PzuyqO8XkzUUEjNZd_gx/w640-h640/ve4oy_1972.jpg" width="640" /></a></div><p style="text-align: left;">The year was 1972. I was newly licensed (VE4OY) and 15 years old. In the months after I earned my license I was thrilled to work anyone who could copy my weak signal. DX was difficult. It would be two more years before I seriously caught the contesting bug and then another year until I put up my first tower.<br /></p><p></p><p style="text-align: left;">Those of you familiar with old equipment will recognize that the receiver was a Hammarlund HQ129X. I bought it from an older ham who no longer needed it. It was by far the most expensive component of the station. It was general coverage with band spread for the ham bands. Even with a new tube and replacement of select capacitors the local oscillator barely functioned on 15 meters and rarely on 10. Tuning on those bands was so touchy that it was difficult to receive CW and SSB. We were slipping into a solar minimum so it hardly mattered.<br /></p><p style="text-align: left;">By the front panel design and colours, the transmitter is clearly a Johnson. I purchased it at a local flea market for very little. Originally a mobile AM crystal-controlled transmitter, a previous owner built an AC supply and added a Johnson VFO. Resolution of the VFO dial was so poor that the only way to get on frequency was to swish the VFO back and forth until it was heard in the receiver. The tubes on top of the VFO are merely for show.</p><p style="text-align: left;">I never did figure out a good way to remove the modulator tubes so all three of the 807's had to be lit. I stuck a flea market open frame 117 VAC relay on top of the power supply for T/R switching of the coax with the knob provided on the receiver. A short length of RG58 through the window frame connected to a 40 meter dipole up ~15' (4.5 m) that was used on all bands. I later added 20 meters to make it a fan dipole.<br /></p><p style="text-align: left;">Without any metering (the one you see was not functional) I burned through a succession of 807 tubes due to high SWR and poor tuning. Used ones were cheap at local flea markets. The soft ones were plugged into the modulator tube sockets to keep the filaments of the others lit.</p><p style="text-align: left;">I used that equipment for a year. In 1973 we moved to a new house and with money from a summer job I upgraded to an HQ170 and HT32B. In 1975 I purchased a brand new FT101B and put up a tower with a TH3jr and 40 meter inverted vee. </p><p style="text-align: left;">That kept me going until 1979 when I earned my M.Sc. and moved from Winnipeg to Ottawa. But that's enough woolgathering. If you want more, tune in to my <a href="https://www.qsotoday.com/podcasts/VE3VN">2023 interview</a> on QSO Today.<br /></p><p></p><br />Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com0tag:blogger.com,1999:blog-6207999661586171874.post-14094406351570788482024-02-29T19:19:00.001-05:002024-02-29T19:19:36.900-05:00Reversible 40 Meter Moxon: Initial Model<p>I would like to retire the XM240 this year. It is not just because of its low efficiency due to the loading coils. When I side mounted it <a href="https://ve3vn.blogspot.com/2023/10/rearranging-yagis.html">last fall</a>, I did it with the full knowledge that I was impairing my flexibility on 40 meters since it can only be rotated through about 130°. It works well for working most of North America, and DX further afield to the south and west. But I miss having two antennas with full rotation.</p><p>I prefer to keep the <a href="https://ve3vn.blogspot.com/2021/09/side-mount-for-limited-rotation-yagi.html">limited-rotation side mount</a> rather than replace it with a swing gate. The latter would allow 300° rotation, which is more than adequate for my needs. There is a 60° arc between 100° and 160° bearing that I can omit without serious loss of station effectiveness. When that direction is needed for long path contacts (e.g. Asia) and southern Africa, the <a href="https://ve3vn.blogspot.com/2021/12/lighting-up-3-element-40-meter-yagi.html">high 3-element yagi</a> is a superior choice, and it is fully rotatable. The offset mount of a swing gate requires robust construction and a strong rotator for the mechanical load of a 40 meter yagi.</p><p>After consideration of alternatives, I returned to an antenna design that I <a href="https://ve3vn.blogspot.com/2015/05/exploring-w6nl-40-meter-moxon-with-model.html">chose against</a> several years ago: the W6NL 2-element Moxon. It's relatively small, has good F/B and broad SWR bandwidth, at the expense of modest gain and the narrow gain bandwidth inherent to every 2-element yagi, Moxon or not. However, it does not suit my application without one major modification: making it reversible. </p><p>Reversibility on the side mount would permit 260° coverage and instant switching between, say, Europe and the US. The gaps are between 95°-145° and 275°-325°. There are few stations to work in those directions and, as already mentioned, there is the big 3-element yagi for those directions. The Moxon is small enough that my ancient (and multiply refurbished) Ham-M rotator can handle it.</p><p>The actual W6NL design works pretty well but it has <a href="http://www.k3lr.com/engineering/moxon/40mMoxon2018Update.pdf">a few unusual characteristics</a>. The modelled SWR bandwidth appears to be narrower than a traditional Moxon rectangle, gain is slightly less and I worry about the capacitance hats striking each other when it's windy and their inconstant separation. The latter is a critical parameter of the Moxon design.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEifquD6mYd0OnBYJjl6sZ-8wsQPt7M2Fj4FM3A7m-8TDS1rGI_7TO4jcai63ighugTKJTTr1UJnVthFaggBCcoPq55I0GkaP6d4zh1uXX8LNz3aLZvay_zPwc9sm564TLoDASDAClA4YmWnlf-dXOHDV-37Oic1rJzMYM6ueb8rorPubRwXLH8zf5hIrCtl/s291/40m_moxon_rectangle_reversible.png" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="198" data-original-width="291" height="198" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEifquD6mYd0OnBYJjl6sZ-8wsQPt7M2Fj4FM3A7m-8TDS1rGI_7TO4jcai63ighugTKJTTr1UJnVthFaggBCcoPq55I0GkaP6d4zh1uXX8LNz3aLZvay_zPwc9sm564TLoDASDAClA4YmWnlf-dXOHDV-37Oic1rJzMYM6ueb8rorPubRwXLH8zf5hIrCtl/s1600/40m_moxon_rectangle_reversible.png" width="291" /></a></div><p style="text-align: left;">For these reasons I decided to explore and compare alternative approaches. I hoped to gain insights into their relative performance, both electrical and mechanical. Any 40 meter rotatable yagi is a large antenna and there may be good reasons to compromise electrical performance in favour of mechanical robustness.</p><p></p><p>The baseline model I developed is a <a href="https://www.dxzone.com/qsy17044-40m-reversible-moxon">symmetrical Moxon rectangle</a>. It is not novel since others have made similar antennas, but I didn't have a model in hand that I was comfortable with. </p><p>I proceeded by keeping the symmetric rectangle dimensions close to those of the traditional (asymmetric element) Moxon rectangle and placing a coil at the centre of the reflector. The coil lowers element resonance so that it has the proper reactance
(phase shift) to be a reflector at the operating frequency.</p><p>In a real antenna the coil and feed point are switched to reverse the yagi but this is not necessary in a model since the switching system does not affect the antenna when properly implemented. The switching system can introduce coupling and stray reactance that
are not part of the model but must be dealt with during construction and
testing of the antenna.</p><p>To meet my criteria the antenna must have these features:</p><ul style="text-align: left;"><li>Symmetrical: two identical elements</li><li>Critical coupling: element tips are placed near each other <br /></li><li>Switchable: driven element and reflector; the reflector has a coil at the centre</li><li>Switching system: method for selecting which element is driven and which is the reflector <br /></li></ul><p></p><p>Exploration is a multi-step process. The first model uses constant diameter elements -- 25 mm in this instance -- with each element tuned to 7.0 MHz. That allows NEC2 to handle the antenna reasonably well since <a href="https://forums.qrz.com/index.php?threads/moxon-with-tapered-aka-stepped-diameter-elements.844412/">SDC (stepped diameter correction) is avoided</a>, and EZNEC's SDC does not support bent elements well. Element dimensions and coil value were varied until the performance was approximately equal to that of a traditional (asymmetric) Moxon rectangle. </p><p><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgHVwUJyLpzxWC7ElUVwQjqoyo-0lAIhaRlZv27CaqUJxJpSNShIGd-_IR8GC3yaiDzgSuOahC7ZjOrC8tynwORPUhlCTLAJJZYb3HsQTVXltNDn2kS6gVABWLgwB4dBXnaQzWlpunW2jIfUU610aEHHJhhWaC74yMcgdyn0IKQgrS8RBl6tocWgXF-qATO/s699/40m_moxon_rectangle_reversible_swr.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="242" data-original-width="699" height="221" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgHVwUJyLpzxWC7ElUVwQjqoyo-0lAIhaRlZv27CaqUJxJpSNShIGd-_IR8GC3yaiDzgSuOahC7ZjOrC8tynwORPUhlCTLAJJZYb3HsQTVXltNDn2kS6gVABWLgwB4dBXnaQzWlpunW2jIfUU610aEHHJhhWaC74yMcgdyn0IKQgrS8RBl6tocWgXF-qATO/w640-h221/40m_moxon_rectangle_reversible_swr.png" width="640" /></a></p><p>When this reversible Moxon rectangle is optimized to this very good SWR, it looks as follows:</p><ul style="text-align: left;"><li>5.6 meter boom</li><li>14.5 meter elements and 2.65 meter inward legs<br /></li><li>30 cm (12") gap between element tips</li><li>1.5 μH reflector loading coil</li><li>Peak gain of 6.6 dbi at 6.955 MHz; Peak F/B of 23 db at 7.1 MHz <br /></li></ul><p>There may be slightly better solutions, but this is pretty typical for a Moxon rectangle. Every 2-element yagi with a reflector as the parasite, Moxon or not, has the maximum gain placed below the band edge so that the F/B and SWR are good across the band. This symmetric Moxon has the same attributes, which will be shown further below. This was a promising beginning.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiSHFcuBlwttBiSsnCpZeB0QokEZDOcyLxLH_JInwOSO4shNBWRSGt1ZuBPtgScgZ-__mkgHLwVTJqjdOzkN7oAQ6beRWlwlAbz-xDG88M4FEqC4gs-WfN85lLgM3azPLUElZIWmuKyRgLkhwdyMroahbbiIjfyBf4Slsp1WDM3KjxVbSimjUDRNtwWbgFZ/s480/ob2-40md_small.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="279" data-original-width="480" height="186" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiSHFcuBlwttBiSsnCpZeB0QokEZDOcyLxLH_JInwOSO4shNBWRSGt1ZuBPtgScgZ-__mkgHLwVTJqjdOzkN7oAQ6beRWlwlAbz-xDG88M4FEqC4gs-WfN85lLgM3azPLUElZIWmuKyRgLkhwdyMroahbbiIjfyBf4Slsp1WDM3KjxVbSimjUDRNtwWbgFZ/s320/ob2-40md_small.jpg" width="320" /></a></div><p style="text-align: left;">There are commercial antennas similar to this, but they're rare due to their size. For example the one from <a href="http://www.optibeam.net/index.php?article_id=104&clang=1">Optibeam</a> is electrically shortened. The performance penalty is modest, but there is one. It is rotatable but not reversible. </p><p></p><p>Take note of the mechanical connection between the element tips. Sagging over the span of the boom length can be significant. Wind and ice demand a robust design for these large elements. I'll return to this later since it's an important structural consideration.</p><p>The W6NL design eliminates the sag problem by making each element horizontally balanced. The inner legs, that make it a type of Moxon, are one half of each capacitance hat. The element tips are extended which moves the hats inward. There is less stress at the ends of the elements. It is possible to design this style of yagi without element trusses if the elements are made sufficiently strong (and heavy).<br /></p><p>However, the <a href="http://www.kkn.net/dayton2004/W6NL_40M_MOXON_YAGI.pdf">W6NL Moxon</a> (whether built from scratch or as a <a href="http://www.k3lr.com/engineering/moxon/W6NL_Moxon104.pdf">modified XM240</a>) is not symmetrical and it is therefore not reversible. For this modelling exercised I instead explored modifications of the basic design that are symmetric.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhm2xbGT5LNX7cxM4CMyU56C5x3dyDpkVwqD07kK7-5OSdjihPXMPx9WN9kXRP7gfLHj6J4pwZ61l6t8P1IToN4x9DaZBJLKR5xfVEB_EtPc2hw3ENRgLtg-Xlh_XM_gWsFO_KwKcZVZfWnxjygGj92XJ0wvTtXjzpHNqf1S5MLBEUebeJrJlEqYKYpewUE/s567/moxgen-1.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="426" data-original-width="567" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhm2xbGT5LNX7cxM4CMyU56C5x3dyDpkVwqD07kK7-5OSdjihPXMPx9WN9kXRP7gfLHj6J4pwZ61l6t8P1IToN4x9DaZBJLKR5xfVEB_EtPc2hw3ENRgLtg-Xlh_XM_gWsFO_KwKcZVZfWnxjygGj92XJ0wvTtXjzpHNqf1S5MLBEUebeJrJlEqYKYpewUE/s16000/moxgen-1.gif" /></a></div><p style="text-align: left;">The diagram comes from <a href="https://www.antenna2.net/cebik/content/moxon/moxgen.html">Cebik's article</a> that does a deep dive into the Moxon rectangle. The critical parameters are shown. There is the ratio of the length to the width and the gap between element tips. There is a dependence of k (ratio of wire diameter to wavelength) which I will skip over in this article since it isn't particularly relevant. Also, I use symmetric elements with loading rather than element length to tune them.</p><p></p><p>Element topology contributes to gain. The greater the length of the parallel element sections, the greater the gain; the tip radiation cancels in the far field due to their symmetry. The gap, C, determines the coupling, for which we need the best value to achieve the Moxon's particular advantages with respect to impedance, SWR bandwidth and F/B.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhGLjmlNFSQXc_6KIMP30TY9cc8ajKhtN5htaD5Vpfoa7sEZaVhnSLodP0GNXVs7ZNt5GUKFV95_KAQYW8zh-zrzSVse75u1JAIGcYadmt3ou1KXXhhhUXNReOKoKTA0IpRu-Z7qIfOBKkuJEBrpYC-L1PXpmDC48pbwWQkczOIZwU7HnDTfOIuGd8ZiOm0/s962/40m_moxon_variations2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="316" data-original-width="962" height="210" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhGLjmlNFSQXc_6KIMP30TY9cc8ajKhtN5htaD5Vpfoa7sEZaVhnSLodP0GNXVs7ZNt5GUKFV95_KAQYW8zh-zrzSVse75u1JAIGcYadmt3ou1KXXhhhUXNReOKoKTA0IpRu-Z7qIfOBKkuJEBrpYC-L1PXpmDC48pbwWQkczOIZwU7HnDTfOIuGd8ZiOm0/w640-h210/40m_moxon_variations2.jpg" width="640" /></a></div><p style="text-align: left;">I explored these three variants. The one on the right is the most similar to the Moxon rectangle. On the left is the one most similar to the W6NL design; the element tips are short since I did a screen capture while I was playing with the model. In the centre is a hybrid where the capacitance hats are at the ends of the elements; it looks like a Moxon rectangle with outward arms at the 4 corners.</p><p></p><p>I found that the critical gap between element tips was around 30 cm (12") for all of these 40 meter variants. Moving away from that value in either direction had a large effect on the 50 Ω match, and a more gradual effect on the F/B bandwidth. In all cases the wire diameters are 25 mm (1") along their entire lengths. The choice is justified since this is a design exploration, not a construction article.</p><p>The symmetric Moxon on the right has a few interesting features. It works best when the boom length (width) is 5.6 meters (18'-4"), with respect to gain and F/B. After many trials, the same was found for the other two designs. The surprised me since the W6NL Moxon has a longer boom. Shortening the boom had the effect of making the elements longer and the capacitance hats shorter to compensate. When the booms are 5.6 meters, the capacitance arms are identical for all three: 2.65 meters. The outer arms for the two with T-hats are also 2.65 meters for mechanical balance.<br /></p><p>Notice that the length to width ratios for the two on the left are lower than that on the right. The maximum gains are a little lower due to the shorter elements. That is due to loading by the hats. </p><p>The element tips on the symmetric version of the W6NL Moxon proved to be a problem. The longer they were the worse the gain and match (I didn't closely monitor the F/B during the process). The problems mostly vanished when the tips were reduced to zero length, which is the T-hat version in the middle diagram. I can't give a definitive reason based on a cursory inspection of the models other than to say that the coupling between elements is less than critical due to the greater distribution of high-impedance points where capacitive coupling is under-utilized. </p><p>I therefore discarded the design on the left and focussed on the remaining two. After coarse optimization I compared their performance.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgArtzX3CzhMc2qNlRhOoe-DuxKUaK5a-zR-S4JmO1GFhdwzn75syXE83qzp9uArNfpiDC1oX0UjAk0XLZeR1kAR1jyEnhzqKGzjgfTbmooBoNHeXeL2HoyhyyUMtEIlxzSt_SMYPzaAJdvI32vW2BsJkshcwFa-pOzvNH2sNrYNcyxLLCfe40Fyppz1m6s/s541/40m_moxon_reversible_gain-fb_t-hat_vs_rectangle.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="301" data-original-width="541" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgArtzX3CzhMc2qNlRhOoe-DuxKUaK5a-zR-S4JmO1GFhdwzn75syXE83qzp9uArNfpiDC1oX0UjAk0XLZeR1kAR1jyEnhzqKGzjgfTbmooBoNHeXeL2HoyhyyUMtEIlxzSt_SMYPzaAJdvI32vW2BsJkshcwFa-pOzvNH2sNrYNcyxLLCfe40Fyppz1m6s/s16000/40m_moxon_reversible_gain-fb_t-hat_vs_rectangle.png" /></a></div><p style="text-align: left;">Gain and F/B are sufficiently similar that we can declare them to be effectively equal. The gain of both is a little less than that of a traditional 2-element yagi with a reflector element and slightly longer boom. Both plots are continued below the band edge to demonstrate that gain increases, which is typical of all 2-element reflector yagis, Moxon or not.</p><p></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGa4t1jTapOFTtCC2NaGJPr7dID8xHw9vq0akVOVmxOnR2XR8W6mKqqnFJJkaFyoR4qPg7j2C6vFh7X7YUgu2zy52CoeD1tcGOk_7ukCL4xzZR_qVWfDM28h_zJgu4d7GyeJryclwtylEQdGILMFdeYIrn5Uog2riGSX4ECuV-4ylsl6i_9ZFaNUYcHRiO/s699/40m_moxon_rectangle_reversible_swr.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="242" data-original-width="699" height="222" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGa4t1jTapOFTtCC2NaGJPr7dID8xHw9vq0akVOVmxOnR2XR8W6mKqqnFJJkaFyoR4qPg7j2C6vFh7X7YUgu2zy52CoeD1tcGOk_7ukCL4xzZR_qVWfDM28h_zJgu4d7GyeJryclwtylEQdGILMFdeYIrn5Uog2riGSX4ECuV-4ylsl6i_9ZFaNUYcHRiO/w640-h222/40m_moxon_rectangle_reversible_swr.png" width="640" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj3XCjuQCvNgUWdwpambzCq6VClIeaTzTflMcAoAgEITraoJzMZ7kdo_jHean3yGU7F6KZTcuLgsglj5hPmsCGsXcsH7rdtKvZMn5P4CAmIrIQ6ya9ben55U0eLGqZRl4YadXG1HQxV8O1pLYv_SGAenWCHWB80PJWXuPGJC1u3sa_SygxAtKb_OvCiWM1c/s729/40m_moxon_t-hat_reversible_swr.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="291" data-original-width="729" height="256" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj3XCjuQCvNgUWdwpambzCq6VClIeaTzTflMcAoAgEITraoJzMZ7kdo_jHean3yGU7F6KZTcuLgsglj5hPmsCGsXcsH7rdtKvZMn5P4CAmIrIQ6ya9ben55U0eLGqZRl4YadXG1HQxV8O1pLYv_SGAenWCHWB80PJWXuPGJC1u3sa_SygxAtKb_OvCiWM1c/w640-h256/40m_moxon_t-hat_reversible_swr.png" width="640" /></a></div><p style="text-align: left;">The impedance matches are also very similar and quite good right across the band. The Moxon rectangle is on the top and the T-hat on the bottom.</p><p></p><p>Since their electrical performance is about the same we turn to the mechanical parameters. These can be as critical as performance considering the large size of 40 meter yagis. Regarding the electrical and mechanical performance of the W6NL Moxon, I suggest reading <a href="http://www.k3lr.com/engineering/moxon/40mMoxon2018Update.pdf">this paper by W8WWV</a>.<br /></p><p>There are several parameters to consider:</p><ul style="text-align: left;"><li>Element length</li><li>Element balance</li><li>Weight</li><li>Wind & ice load <br /></li><li>Maintaining the distance between element tips</li></ul><p>First, let's compare the total linear lengths. For the symmetric rectangle, each half element is 7.25 meters and the inward sides are each 2.65 meters, for a total length of 19.8 meters. For the T-hat version, each half element is 5.9 meters and each T-hat arm is 2.65 meters, for a total length of 22.4 meters. The elements of the latter are shorter but the arms at the ends of the elements, where they are weakest are double that of the rectangle.</p><p>The T-hats are balanced on the element ends while the inward arms of the rectangle are not. The torque on the end of the element is a concern with the rectangle. It can be partially mitigated by a fibreglass rod to fix the gap distance and mechanically couple the arms of the opposing elements. However, the long span of 5.6 meters of, hopefully, lightweight tubing requires more mechanical strength than for the similarly coupled arms of the balanced T-hats.</p><p>The arms of the rectangle design require a stronger design than for the T-hats, and that may be a greater threat than the nominally lighter rectangle. Element trusses do not solve the problem. The T-hat design might not even need element trusses if the elements are made sufficiently strong. Since the T-hats are weight and load balanced, the 5.6 meter inner span between the elements might only need attention with respect to stress caused when the elements experience unequal loading in a strong wind.</p><p>It's a dilemma and I have no good answer at the moment. You could say the electrical performance is the easy part of the antenna design. Although I have enough aluminum in my stockpile to increase the strength of the elements, there is a greater risk of breakage at the centre since both elements must be split for feeding and for switching in a series coil. The elements must also be electrically isolated from the boom. The mechanical design is challenging.</p><p>That will be my next step. Until I have a robust mechanical design I will not make a final determination on whether to proceed with a rectangle or T-hat design. The basic mechanical design is common to both. </p><p>There are alternatives like the <a href="https://ve3vn.blogspot.com/2016/04/height-vs-gain-40-meter-yagi.html">NW3Z 3-element yagi</a> and yagis with <a href="https://ve3vn.blogspot.com/2013/12/40-meters-wire-yagi-diamond-vee-elements.html">two V-shaped elements</a> that do away with the high load at the ends of the elements, but those come with an additional performance penalty: they are not true Moxons and gain is reduced by the smaller effective element spacing.<br /></p><p>I'll end with an additional concern for both designs: potential for interactions. The XM240 is not resonant on the third harmonic which would otherwise fall within the 15 meter band. I included <a href="https://ve3vn.blogspot.com/2020/03/40-meter-dilemma-interactions-size.html">capacitance hats on the 3-element yagi</a> to accomplish the same. It was therefore important to know how the reversible T-hat and rectangle designs fare in that respect.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEirwmmUujo6_vIVdgm2Wdneq4F45vEM5kf9Ha56dyhyphenhyphen2trXI3EmPZrL9FsnybtN1riZkcxqbjpZGryv0Rwl5-jIXunf-jKWargFwxLI-DIVNyh8lj2fAdAzPZTOjHJKNwZ6NsDejmR7aQ8DqIWeZ5thi9-f8x5vSaXyPt7B-yDqDvrca1i21I9srH8vAc64/s729/40m_moxon_rectangle_reversible_sweep.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="291" data-original-width="729" height="256" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEirwmmUujo6_vIVdgm2Wdneq4F45vEM5kf9Ha56dyhyphenhyphen2trXI3EmPZrL9FsnybtN1riZkcxqbjpZGryv0Rwl5-jIXunf-jKWargFwxLI-DIVNyh8lj2fAdAzPZTOjHJKNwZ6NsDejmR7aQ8DqIWeZ5thi9-f8x5vSaXyPt7B-yDqDvrca1i21I9srH8vAc64/w640-h256/40m_moxon_rectangle_reversible_sweep.png" width="640" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg7HUU_iLfIJNwCUlDwL1R4yq0ipXfVWioo4taHqy-RSjUgoqrJe9GXzEQQU60osSKuR5ChSh8t78lknBaPFrX0PAED0RPJUqNSUwDVLu61alCiOY1drOfXslBHCVDJWa0xf5dWvOrWqScX9_K7-CdJfc52nOtQckm6NMIL2jb0G655GWNLEpZPuAdg9wll/s729/40m_moxon_t-hat_reversible_sweep.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="291" data-original-width="729" height="256" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg7HUU_iLfIJNwCUlDwL1R4yq0ipXfVWioo4taHqy-RSjUgoqrJe9GXzEQQU60osSKuR5ChSh8t78lknBaPFrX0PAED0RPJUqNSUwDVLu61alCiOY1drOfXslBHCVDJWa0xf5dWvOrWqScX9_K7-CdJfc52nOtQckm6NMIL2jb0G655GWNLEpZPuAdg9wll/w640-h256/40m_moxon_t-hat_reversible_sweep.png" width="640" /></a></div><p style="text-align: left;">The SWR sweep of the rectangle is at the top and the T-hat is on the bottom. Both meet my objective of avoiding resonance on any contest band, and especially 15 meters. I was not really concerned since loaded elements (which includes the non-linear element profile of the Moxon rectangle elements) shift the third harmonic away from its simple arithmetic value.</p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com0tag:blogger.com,1999:blog-6207999661586171874.post-25451888145799518222024-02-22T12:06:00.002-05:002024-02-22T12:46:41.738-05:00ARRL DX CW - M/2 @VE3JM<p>When I was young and without a station or just a small one, the only way to do an effective multi-op contest operation was from others' stations. I don't do it very much these days. When my friend Vlad VE3JM asked me to join his team for ARRL DX CW, I welcomed the opportunity. I <a href="https://ve3vn.blogspot.com/2018/11/contesting-big-and-small.html">operated there</a> several years ago for CQ WW SSB. His station has changed a lot since then.<br /></p><p>As readers likely know, I have a "<a href="https://ve3vn.blogspot.com/2023/11/on-becoming-big-gun.html">big gun</a>" station of my own now, and that I've hosted multi-op teams for two contests so far: <a href="https://ve3vn.blogspot.com/2023/11/cq-ww-ssb-m2.html">CQ WW SSB</a> and CW. There are good reasons for operating from another station for a major contest despite having my own big station:</p><ul style="text-align: left;"><li>Opportunity to team up with contesters I haven't operated with before</li><li>See how other big guns design their stations<br /></li><li>Learn new strategies and operating styles</li><li>Learn to use and assess other software packages, equipment and switching systems</li><li>Less worry about problems arising and the stress of being the one to fix them</li><li>Have fun!<br /></li></ul><p>There was one more reason: my station is experiencing several technical problems that would have seriously impacted a contest operation. None are major but it was impossible to deal with them in time for the contest. With luck and good weather I hope to be ready to try another multi-op for the ARRL DX Phone contest in March. If problems persist I may enter single-band single-op.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEilwV31ttR3Oe5N-04U9j165KtGWznfGy-GEEk1_EmnLnz-BR5xoigIz-p18Tr1n3kqj_KabPufBtKyPVBG31GahnL1bnZjIQJiya1SEYBMWNvN3gz5op_IdXX5R2Jif2GV8EWvwTPgN0WSPL0fMv-uIoBOortpm_caAM_eroh9L61bLdgy1CTctpMNGEkq/s640/ve3jm_new_tower.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="595" data-original-width="640" height="373" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEilwV31ttR3Oe5N-04U9j165KtGWznfGy-GEEk1_EmnLnz-BR5xoigIz-p18Tr1n3kqj_KabPufBtKyPVBG31GahnL1bnZjIQJiya1SEYBMWNvN3gz5op_IdXX5R2Jif2GV8EWvwTPgN0WSPL0fMv-uIoBOortpm_caAM_eroh9L61bLdgy1CTctpMNGEkq/w400-h373/ve3jm_new_tower.jpg" width="400" /></a></div><p style="text-align: left;">All of us were relaxed enough not to cause conflicts. Rather than five keyed up contesters fighting for the two operating seats, we were all happy to cede the seat when another wanted operating time. When an operator needed a break there was always another ready to step in. When problems arose we calmly worked around them. We were tolerant of our differing tactics for mixing running with hunting. All in all, we worked well as a team.</p><p></p><p><b>Antennas</b></p><p>There were several antenna problems. Since Vlad works and has limited time to attend to the station they could not be resolved before the contest. Even so we did well. Put enough aluminum up high and magic happens despite not always being able to turn the antennas or use all the yagis in a stack.</p><p>We had stacks on 20 and 15 meters, two tri-banders, a 10 meter yagi, two yagis on 40, an 80 meter 4-square and one of the big towers served as a vertical on 160 meters. There was one receive antenna.<br /></p><p>More antennas would have been nice but, again, that has to wait until he has time. The picture shows his newest tower with only an XM240 at 140'. There is ample room for more antennas. With time they are certain to appear.<br /></p><p><b>Equipment</b></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyp75z5hP4JTSO2FdnRmde6J8tl0LhvOd4qgWP5rCrLhJQ16su2jnVJnB3AD2qy4oIRgO4KMJ5z43lQy8x47CEDT8RDIaeKhvm1CItimQglqLw_ZbLmUJKdwJXtMvALF3lbZKuss8aa1voWl_rv1y54g3iwV36NNXj3gqM7XuPOKdS1zkqHuxZUuHnkcd8/s600/ve3jm_allstations_manned.jpeg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="475" data-original-width="600" height="253" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyp75z5hP4JTSO2FdnRmde6J8tl0LhvOd4qgWP5rCrLhJQ16su2jnVJnB3AD2qy4oIRgO4KMJ5z43lQy8x47CEDT8RDIaeKhvm1CItimQglqLw_ZbLmUJKdwJXtMvALF3lbZKuss8aa1voWl_rv1y54g3iwV36NNXj3gqM7XuPOKdS1zkqHuxZUuHnkcd8/s320/ve3jm_allstations_manned.jpeg" width="320" /></a></div><p style="text-align: left;">Both stations had venerable Elecraft K3 transceivers and pan adaptors. I've only ever used the K3 during contests at other stations so there is a brief learning curve every time. The pan adaptor controls took getting used to since I had never used that K3 accessory. There were occasional receiving artifacts that may have been due to IMD or overload. </p><p></p><p>The third station consisted of a Flex transceiver and a multi-band vertical that was hastily erected. This station was just for listening. It could have been used to work a few multipliers except that there was no interlock with the other two stations. Despite that constraint, it served very well for checking out multipliers and band conditions by one of the three otherwise idle operators.</p><p>In the picture (credit VE3JM) you can see me on the far right at the third station while Nick VE3EY (foreground) and Dave VE3KG operate the main stations. </p><p>Amplifiers were a manually tuned AL1200 and an auto-tune Flex PGXL. Despite the automatic band switching and tuning, the PGXL cannot be ignored entirely. It reacted to antenna matching difficulties such as one yagi that became intermittent, and again when we were hit by a snowstorm that altered impedances of the antennas. Although the AL1200 had to be manually tuned, it was easy to compensate for impedance changes and the grounded grid design was tolerant of imperfect tuning. </p><p><a href="https://va6am.com/">High power BPF and tri-plexers</a> are by Pavel VA6AM. They work extremely well. I have his prototype 6-band low power BPF in my station, which also work very well.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMtKr8GfjDWdmzbNuEA8KNbyKYr3zXsKbRlglIFY52Eaqlmmz5BwkvFRer0ZyTUmuy_fl8UqHth4kODfpMDiFJfvIGY-IgOqW80mntRG80hDb-r9ZRb3wJBHQo5MHhGGkqbUw8KeuwlylRhT9W2D5zap98Mwv3mQNhwixNxfNgnr1UfKhq3kzWTJgGnHvx/s800/ve3jm_dxlog_display.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="458" data-original-width="800" height="366" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMtKr8GfjDWdmzbNuEA8KNbyKYr3zXsKbRlglIFY52Eaqlmmz5BwkvFRer0ZyTUmuy_fl8UqHth4kODfpMDiFJfvIGY-IgOqW80mntRG80hDb-r9ZRb3wJBHQo5MHhGGkqbUw8KeuwlylRhT9W2D5zap98Mwv3mQNhwixNxfNgnr1UfKhq3kzWTJgGnHvx/w640-h366/ve3jm_dxlog_display.jpg" width="640" /></a></div><p style="text-align: left;"><b>DXLog</b></p><p></p><p>I've never used <a href="https://www.dxlog.net/">DXLog</a> before, but I've wanted to give it a trial run for some time. It was a necessity for this contest since the antenna control and automation are integrated with DXLog. VE3JM uses the same basic system developed by K3JO for the K1LZ super-station. Perhaps it was my bias due to my long experience with <a href="https://n1mmwp.hamdocs.com/">N1MM</a> that I didn't really like it. That said, it did some things very well and has features that I have not (yet) considered for my home brew station automation.</p><p>The screenshot is that of the third station. The screen includes the Flex system and a browser window monitoring the contest scoreboard. The log entry window is at the bottom left. This is far busier than the two main stations that each has two displays. The lack of screen real estate wasn't a problem since the stations wasn't used for making contacts. The information display was all we needed to monitor our contest operations and to assist with the choice of operating tactics.</p><p>One of things I didn't like was the default colour schemes and fonts used in several windows that are not easy to read with older eyes. We made a few changes to increase the colour contrast. Most of the time it didn't matter since the operators were focussed on only a few windows. The window for available multipliers and contacts was easy to read and used to rapidly pounce on stations. I could run through the list and often work them faster than when running. One call was all it took in most cases.<br /></p><p>The station automation and antenna selection is integrated into DXLog using APIs. I prefer to have the choice of whether to use DXLog or N1MM. For that reason I use RadioInfo UDP broadcasts for my station automation system. I eventually plan to enhance my software to accept RadioInfo messages sent by DXLog. They appear to be <a href="https://ve3vn.blogspot.com/2023/07/musing-on-radioinfo-standard.html">similar and rich enough</a> to support the same functionality I have with N1MM. I don't want to be locked into either contest logger.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh9bEA_ucZe521cGifcU59-AjPmXb8Q1IpxGgPuuBjZlBg-DyjPdSJ3mQsuxXhNh6hF2emKa_o15jw0CPKRD2akTDQ9Rj6TsZKWyQrjY_Mu0fK9q9tjpF3Hj_4z4t3MGZCh-DZuRqPGZEOdSXE6EBg-85SmLDbeNzwDa_0d_B57304oXqFtgfGaJaxJpjvK/s771/ve3jm_online_scoreboard.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="528" data-original-width="771" height="438" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh9bEA_ucZe521cGifcU59-AjPmXb8Q1IpxGgPuuBjZlBg-DyjPdSJ3mQsuxXhNh6hF2emKa_o15jw0CPKRD2akTDQ9Rj6TsZKWyQrjY_Mu0fK9q9tjpF3Hj_4z4t3MGZCh-DZuRqPGZEOdSXE6EBg-85SmLDbeNzwDa_0d_B57304oXqFtgfGaJaxJpjvK/w640-h438/ve3jm_online_scoreboard.jpg" width="640" /></a></div><p style="text-align: left;"><b>Contest scoreboard</b></p><p></p><p>This was the first time I've used the <a href="https://contestonlinescore.com/">contest scoreboard</a>. It never struck me before as useful or interesting. Vlad set it up for us to track our score against the other major M/2 competitor in Canada: VA2WA. I won't say that I'm hooked but I was impressed and it did indeed keep us motivated.</p><p>When our score was close to them or other M/2 you could feel the tension and motivation in the shack. I don't know if the rate increased because of it but we became more aware of available multipliers and chased them. We started slow on Friday due to technical issues so it took many hours to catch up to the competition. In the end we did and finally overtook them. Although that was our primary objective, we also watched how we did relative to our closest American competitors N2NL and K9RX. We had little hope of catching K9CT and W3LPL, the former with superior antennas and the latter also having a superior location. Nevertheless it was fun to watch.<br /></p><p>Racking up the QSOs and multipliers takes time so it doesn't help to pay too close attention. We were always curious about which bands they appeared to be running or chasing mults. That made us rethink our tactics: were they the best or should we try something different. Most competitors reported band break downs which were very useful to understanding what they were doing in near real time. I enjoyed that aspect of the competition so much that I let others operate more so that I could spend time considering strategy. When advisable I would make suggestions to the operators. </p><p>I can't say that the contest scoreboard helped us do as well as we did but it certainly made us pursue tactics that would boost our score. It is unlikely that I'll use the scoreboard often other than for multi-ops. I am less curious about the activity of others when I operate by myself.<br /></p><p><b>Operating styles and tactics</b><br /></p><p>The fundamental strategy for an M/2 entry can be summarized by one word: run. The only reasons not to run are to chase multipliers or to call other runners. The S & P sessions are brief and intense, and are usually interspersed with CQs. That is, when there is no response to a CQ you click on a spot, call and hopefully work them. </p><p>Whether or not you work them, you immediately return to the run frequency and CQ again. Speed is of the essence. If you fail to work them, repeat the cycle.<br /></p><p>S & P sessions last longer only when runs are particularly dry. A band change is often the more productive option. Band changes are otherwise only justified to run faster or to chase multipliers. Counting band changes is critical since each station is permitted 6 per clock hour (e.g. 1300Z to 1459Z); 8 are allowed in CQ WW. Changing bands and back again counts as two band changes so you have to pay close attention to the countdown window (DXLog and N1MM both have this feature). We would use unused band changes late in the hour to chase multipliers just before they reset to 6.<br /></p><p>The third operator, when there was one, monitors activity levels and available multipliers and makes suggestions to the operators on desirable bands and openings, and spotted multipliers. Runs from a big gun station can be intense so the operator might not immediately notice the spots. In all cases it was the operator that made the choice of what to do and when.</p><p>Other tactics were minor in comparison to the ones mentioned above. For example, which antennas to use, individually or in a stack, </p><p>Those who were not operating did errands for the operators. This included delivering food, drinks and snacks. There was almost always someone on deck, ready to jump in when an operator needs a break. With 5 operators there was plenty of time to chat and sleep. Since I'm a nighthawk, I left most of the high band running to the others during the day so that I could operate overnight. My time to quit was after the gray line openings on the low bands were done soon after dawn.</p><p>Late in the contest we celebrated every multiplier and eagerly watched the scoreboard to see how it would change our position. The scores were often very close and every multiplier or brief run had a large impact. It was tremendous fun.</p><p><b>Conditions</b></p><p>This was one of those rare contests when propagation conditions were exceptionally good. What was particularly unusual was that all 6 bands were hot. 10 meters opened at sunrise and didn't close until hours after sunset. 160 meters delivered openings in all directions and the multiplier counts show it. We worked at least one QRP station in Europe. Even 20 meters performed well throughout the day. It is often suppressed midday by D-layer absorption that increases during a solar maximum.<br /></p><p>The solar flux was high but not very high. Days of quiet geomagnetic conditions leading up to the contest appeared to be a major contributing factor.</p><p>A good example of the low absorption was the propagation on 40 and 80 meters. Our run rate to Europe continued for hours after their sunrise. We were astonished to be called by Europeans on 40 meters as far south as Italy a full 3 hours after their sunrise. The daylight openings were shorter on 80 meters but still exceptional. I haven't seen such quiet conditions in a major contest since the solar cycle minimum. </p><p>Quiet geomagnetic conditions that last for days are unusual at a solar maximum. Sunspots are constantly erupting and sending radiation and particle streams our way. Nor were there any flares to cause radio blackouts during the daytime. </p><p>Yet geography still matters. Stations south of us were able to reach a little further for a little longer. That raised their QSO totals relative to those of us further north. With the bulk of contest QSOs between North America and Europe (80% or higher), geomagnetic latitude matters. Multiplier potential was more equitable since those come from all directions. We were not disadvantaged in that respect.<br /></p><p><b>Going home</b></p><p>After sharing a post-contest meal we went our separate ways. Leaving was not easy. Not because of the camaraderie but because of the awful weather and road conditions. We were beset by heavy snow squalls and high winds that made driving treacherous. Although the plows were doing their best on a Sunday evening, speeds were slow and the accident potential high. </p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiaN-6Yt2BcaWzsMBhK2Jmibt3EEPeztPSZ41Ep9lovY6F79IbK8WV2z7dKBeeDpHQYT5c4ZtDnS1xyBLfL8ip3wSFkXqeCXcX8NoH4kqpZGYtqkhkE205bIaNa1jGQObYHLbqanX1Qa7BmppKKf04GIUr6IZ-JGUjT8xi0SrvTqyoXx1eKSDggZ9K2C140/s300/snow-squall-driving-in-canada-tatiana-travelways%20small.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="200" data-original-width="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiaN-6Yt2BcaWzsMBhK2Jmibt3EEPeztPSZ41Ep9lovY6F79IbK8WV2z7dKBeeDpHQYT5c4ZtDnS1xyBLfL8ip3wSFkXqeCXcX8NoH4kqpZGYtqkhkE205bIaNa1jGQObYHLbqanX1Qa7BmppKKf04GIUr6IZ-JGUjT8xi0SrvTqyoXx1eKSDggZ9K2C140/s16000/snow-squall-driving-in-canada-tatiana-travelways%20small.jpg" /></a></div><p style="text-align: left;">When near zero visibility whiteouts greeted us on the major highways, the semis took control and kept me safely on the roadway. Luckily we all got home without incident. It was not the best way to end the weekend. The <a href="https://pixels.com/featured/snow-squall-driving-in-canada-tatiana-travelways.html">photo at right</a> gives you an idea what it was like, except that the highway was wider, the traffic heavier and it was dark with headlights only serving to blind drivers from the bright reflection off the heavy snowflakes.</p><p></p><p>Despite the commute challenge, the contest was well worth the trouble. As many have noted, conditions were outstanding on all bands and the activity high. Many records fell that weekend. If our score holds up we will have set a new Canadian M/2 record. That would be a nice accomplishment for a fun weekend with good friends.only show totals<br /></p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com0tag:blogger.com,1999:blog-6207999661586171874.post-41389398573559366652024-02-14T11:04:00.001-05:002024-02-14T11:04:42.503-05:00GPIO Protection From an Op-amp Circuit<p>I have finally begun the design and implementation of a new controller for my two prop pitch motor rotators. The "legacy" controller is home brew by a previous owner. It is ugly and has problems, and the "temporary" <a href="https://ve3vn.blogspot.com/2022/10/prop-pitch-motor-direction-indicator.html">outboard op-amp circuit and meter</a> are especially unsightly. The time has come to eliminate it from my desktop.</p><p>The plan is for the power supplies to be placed out of sight under the operating desk, and operated from a lightweight and ergonomic controller on the desktop. The controller will be software based using an Arduino. There are several components:</p><ul style="text-align: left;"><li>Two 24 VDC power supplies, with switching for the AC and the clockwise and counterclockwise direction wires; I have two power supplies but I want to rehouse them in a new enclosure<br /></li><li>Digital display of rotator direction using op amp circuits driven by the existing <a href="https://ve3vn.blogspot.com/2022/04/direction-pot-for-upside-down-prop.html">direction pots</a> on the towers</li><li>Manual activation via push buttons, and eventually supplemented by software controls</li><li>Software limits and provision for greater than 360° rotation</li><li>Fault detection and protection</li></ul><p>There are commercial products that will do the job. However, as anyone that has followed this blog knows, I like to do it myself. Yes, it is less expensive to home brew, but I like the satisfaction of building what I can. This is not a particularly complex project so it is well within my abilities. There is ample learning to be done along the way, which is a major theme of this blog.</p><p>There will be further articles as the project progresses. In this one I will focus on one design challenge: protecting the Arduino processor from high and low voltage applied to its GPIO pins. The 741 op-amp circuits will employ ±15 VDC supplies and the microprocessor is acutely sensitive to out of bound voltages. Mistakes can happen during construction and during periodic adjustment of the op amp circuits and I want to reduce the risk of bricking microprocessors.<br /></p><p>The maximum allowed range of voltages applied to the GPIO pins of a 5 VDC microprocessor is approximately -0.5 to +5.5 volts, whether for digital or analogue input. The range is narrower for a 3.3 VDC microprocessor, so you must confirm which you are using and choose a different value for D2, a Zener diode, in the following circuit.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiGR8fUgRMjZlyL7cP2TvVMU8zL4LPldESKhpmTQTaI4-9xUxK-Z8fA8_q99oAqUmeKCjllttIfbniOD5-iuDgKN4CGSODwzWxTEEoUkQqyztNgQJtiwcQGEzSqNTAmT9w7Xwen4bw3ZAzmYYcOPFtKmIQJhRdmda3f49VEds5ICxtVOQAL9XGmjubidlNY/s884/gpio_protection_circuit_kicad.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="319" data-original-width="884" height="231" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiGR8fUgRMjZlyL7cP2TvVMU8zL4LPldESKhpmTQTaI4-9xUxK-Z8fA8_q99oAqUmeKCjllttIfbniOD5-iuDgKN4CGSODwzWxTEEoUkQqyztNgQJtiwcQGEzSqNTAmT9w7Xwen4bw3ZAzmYYcOPFtKmIQJhRdmda3f49VEds5ICxtVOQAL9XGmjubidlNY/w640-h231/gpio_protection_circuit_kicad.png" width="640" /></a></div><p style="text-align: left;">One of my recent projects is to learn <a href="https://www.kicad.org/">KiCad</a> to develop custom PCBs. I have a long road ahead so I may resort to my usual use of protoboards for expedience in this project -- my time is limited. Its only purpose here is to draw the schematic of the protection circuit.</p><p></p><p>The purposes of the circuit include:</p><ul style="text-align: left;"><li>Block negative voltage: D1 provides reverse polarity protection from negative voltages<br /></li><li>Limit the positive voltage: R1 and D2 (5.1 volt Zener diode) act as a regulator to keep the voltage well below 5.5 volts<br /></li></ul><p>The potentiometer in the test circuit is used to vary the source voltage from the 9 volt battery over its range from 0 to ~9.5 volts. The battery is reversed to test negative voltage protection. R2 emulates the high impedance of an analog GPIO pin of the Arduino. There are test points to measure the source voltage (A) the voltage drop across D1 (B), and the voltage presented to the GPIO pin (C).</p><p>The objectives of the test:</p><ul style="text-align: left;"><li>Verify blocking of negative voltages and that positive voltages never exceed 5 volts <br /></li><li>Linearity of the circuit</li><li>Voltage range for best linearity</li><li>Component selection for best linearity</li></ul><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjFduzjSbJfcel43IBeycEWqDogz-1M8NG8Vyv1HMafbeCaGjV1UmaFQiR8hz77H7DHmdHPvyrAyxBXKAO4VUahh0XMKLIUEK32XmrajFUAxgOobxrn50UgKEAFOIyPYD36nVuICfBcE4pNrikInXWzcSukFblbpfUvQ3mKrVBGtL_KvUFx1cWTQe0q6vAE/s800/gpio_protection_circuit_test.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="800" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjFduzjSbJfcel43IBeycEWqDogz-1M8NG8Vyv1HMafbeCaGjV1UmaFQiR8hz77H7DHmdHPvyrAyxBXKAO4VUahh0XMKLIUEK32XmrajFUAxgOobxrn50UgKEAFOIyPYD36nVuICfBcE4pNrikInXWzcSukFblbpfUvQ3mKrVBGtL_KvUFx1cWTQe0q6vAE/w640-h480/gpio_protection_circuit_test.jpg" width="640" /></a></div><p style="text-align: left;">A push down protoboard was used for the test circuit. It is easy to substitute components. An inexpensive digital multimeter is used to measure voltage at the test points and to confirm resistor values. Readout precision is 0.01 volt ±0.01 count error. Multimeter accuracy is unknown.</p><p></p><p>Populating the other half of the protoboard is a circuit for testing the use of an LCD display with the Arduino Uno. It will be used for the controller software and display. I'll leave that component of the controller for another article, but I will mention that connecting and using the LCD display was far easier than I anticipated. I was even able to quickly construct the custom characters that I'll need.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhTAFY7Whfg1Cgev1Yd41dFPHeDWIaFng71rgCxs6JQtbAsyM3z4zGq95xAjnZCqEwhDUlLhlHrJlQOSjaC_25Q-duEHBow6qnleFeE8Mh4r83fkCgm_6JnTrA9DtR-XJFniMtNcXMLV96HafRKXexlY-3TK2cYiQBzL2pZNDM0z2oJLj3GnEoVhVOxIB0D/s468/gpio_protection_linearity.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="389" data-original-width="468" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhTAFY7Whfg1Cgev1Yd41dFPHeDWIaFng71rgCxs6JQtbAsyM3z4zGq95xAjnZCqEwhDUlLhlHrJlQOSjaC_25Q-duEHBow6qnleFeE8Mh4r83fkCgm_6JnTrA9DtR-XJFniMtNcXMLV96HafRKXexlY-3TK2cYiQBzL2pZNDM0z2oJLj3GnEoVhVOxIB0D/s16000/gpio_protection_linearity.png" /></a></div><p style="text-align: left;">I varied the source voltage from 0.5 to 5.5 volts in 0.5 volt steps with the potentiometer. I measured and plotted the voltage at test points A, B and C. Lower voltages are cut off by the silicon junction of D1 and higher voltages are rolled off by D2. The linear range, if it exists, must lie between those extremes. I repeated the test with R1 values of 220 Ω and 1000 Ω. A higher R2 may be desirable to limit current and heat dissipation during over-voltage conditions. The B curves are identical (as expected) so the yellow curve is hidden beneath the blue one.<br /></p><p></p><p>The test went so well that I saw no need to substitute components for D1 and D2. Negative (reverse battery) voltage read 0.00 volts at all test points at all potentiometer settings up to the limit of the new 9 volt battery (9.7 VDC) the voltage at test point C never exceeded 4.9 VDC. There is a wide linear operating range for positive voltages. Although this is what I expected it is better to be certain. Those straight lines on data sheets can deviate depending on circuit design.</p><p>The linear range is from 1.0 to 5.0 volts (A), within ±0.02 volts at test points B and C. Linearity is critical for tracking the linear direction pot, assuming linearity of the op amp circuit. Non-linearity, had it been present, can be remedied by an improved hardware design, software compensation based on the circuit's operating curve, or by restricting the voltage to a narrower range where it is found to be linear.</p><p>In my application the target voltage range will be 1.5 to 4.5 volts, representing directions from 0° to 360°. I leave a small amount of the linear range at both ends to exploit the lack of mechanical limits on the prop pitch motor to extend clockwise and counter-clockwise rotation past 180° (due south) by a small amount. The rotation loops can accommodate at least 20° of additional range in each direction. <br /></p><p>Although the choice of R1 did not affect linearity in this test, the value still matters. As mentioned earlier, a higher value serves to limit the current when the source voltage is high. However, a higher value reduces the usable resolution due to voltage division with the load (GPIO pin). Notice the slopes of the red and green lines. I did not measure the current through R1 and D2 during the test.<br /></p><p>For the source voltage range of 1.5 to 4.5 volts, the corresponding range presented to the GPIO pin (C) is 2.8 volts when R1 is 220 Ω and 2.66 volts when 1000 Ω. Thus the centre (north) positions are 2.9 and 2.83 volts, respectively.<br /></p><p>The Arduino has a 10 bit ADC with 1024 values from 0 to 5 volts. We're using a little more than half that, say, 60%. The direction readout is therefore approximately 360 ÷ 600 = 0.7°. The difference may not be so pronounced when connected to an actual GPIO since the input resistance is typically higher than the 10 kΩ used for testing.<br /></p><p>While not a concern for HF yagis, a higher resolution may be desirable for VHF/UHF antennas, but only if the resolution of the direction pot is better than the software resolution. High resolution can be useful for monitoring any antenna system rocking in the wind and to ascertain whether the rotator is moving in the moments after power is applied.</p><p><b>Too simple?</b></p><p>After reading this article you might wonder whether the circuit and its characterization are too simple to require exposition. Simplicity is in the eye of the beholder. For those that live and breathe electronic circuit design, this article might elicit nothing more than a shrug. </p><p>But I'm a ham, not an electrical engineer, although I do know software design. Understanding simple circuits like this is well worth the effort. Walking through the process is likely to be of use to other hams like me. It might even inspire experimentation and home brewing, and that's always a good thing in our technical hobby.<br /></p><p><b>Next steps </b><br /></p><p>The next step is to connect the circuit to the Arduino. The software to convert the voltage to a direction and display it isn't complicated. The op amp circuit to convert the direction pot resistance to the Arduino ADC will be designed to centre its output on the protection circuit's linear range. </p><p>It will be slightly different from the prototype I am currently using since a meter reads current and the ADC reads voltage. The op amp circuit will be adjustable so that no software correction will be needed to derive the correct direction.</p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com0tag:blogger.com,1999:blog-6207999661586171874.post-27836252906575237802024-02-07T22:01:00.003-05:002024-02-07T22:02:14.888-05:00Reflections on CQ 160<p>Single band contests like the <a href="https://www.cq160.com/">CQ 160 Meter</a> contest have a unique character. This goes beyond their particular appeal to aficionados of those bands. Once you've worked a station, that's it; you don't get to work them again. There are exceptions, such as the ARRL 10 Meter contest where you can work stations on CW and SSB if you enter the mixed mode category.</p><p>As the contest progresses there are fewer stations to work and the rate drops. The decline can happen quickly. In last week's CQ 160 contest, my first hour rate was over 130. By the time I quite on Saturday evening the hourly rate was between 30 and 40. Stations that put in a full time effort saw their rates plummet further. If rate is what draws you to contests, these are rarely where you want to be after the first few hours. I took several breaks on the first evening at my convenience and I doubt that my score was impacted despite the high rate that I interrupted -- the stations were almost all there to be worked later.<br /></p><p>Most contesters drawn to single band contests will only stick with it if there are other things that appeal to them. For example, I operated <a href="https://ve3vn.blogspot.com/2023/12/qrp-lessons-from-arrl-10m-contest.html">QRP in the ARRL 10 Meter</a> contest. QRP introduced a self-imposed handicap that made every QSO more challenging, especially DX and DX multipliers. Since a high rate was unlikely, the rate (such as it was) didn't decline as much as it did for higher power stations. I've done this as well in <a href="https://ve3vn.blogspot.com/2022/11/big-station-qrp-in-sweepstakes.html">ARRL Sweepstakes</a> for the same reason since despite being a multi-band contest, you can only work a station once.</p><p>For me, the appeal of the 160 meter contests is DX. That is never easy on top band. Outside of contests, CW activity is very low. While it is nice to see the same DX stations every night, there is little novelty. Watching the ebb and flow of top band propagation is interesting but not enough to keep me there. I am always eager for top band DX since I am <a href="https://ve3vn.blogspot.com/2017/11/160-meter-antenna-at-long-last.html">relatively new</a> to having an effective station.<br /></p><p>Contest weekends significantly raise the activity level, and the CQ 160 Meter contest does it best. The activity level on 160 during CQ WW CW is high but not as high. The difference is that in CQ WW many stations activate rare countries and zones. The potential country haul during CQ 160 is lower but it is interesting to see more activity from home stations.</p><p>With limited DX opportunities and little rate beyond the first hours I chose a non-serious entry in this year's CQ 160 Meter CW contest. I took maximum advantage of the opportunity by operating high power and assisted. I quit the contest when the rate was painfully slow and there was little prospect for improving DX propagation. </p><p>If you want to read more on my thoughts about single band contests like this one, you can find them in several past articles. For example, <a href="https://ve3vn.blogspot.com/2020/12/arrl-160-contest-battle-of-attrition.html">this one</a> about the CQ 160 Meter contest. <br /></p><p><b>Competition</b></p><p>I can't win. This is not a defeatist attitude. I am realistic about the competition in this contest. 160 meters is a tough band to successfully work DX and every decibel counts, and so does geography. Ultimately this contest is one of attrition since there is little difference of contacts and multipliers between similarly equipped top-ranked stations in the same area and entry category. <br /></p><p>The winners have antennas with gain. A typical 4-square or K3LR parasitic array has 3 to 4 db advantage over my single vertical. Power is another area where I fall short. I stay pretty close to the Canadian legal limit. That's a 2 db disadvantage to the US legal limit. Many stations don't respect their countries' power limits. There is little risk of enforcement in either country for stations in rural locales where EMI is low risk.</p><p>When DX signals are riding the noise, those decibels convert to QSOs and multipliers that are out of my reach. I'm not complaining since it is an incentive to pursue <a href="https://ve3vn.blogspot.com/2021/06/driving-arbitrarily-spaced-verticals-on.html">phasing my towers</a> for top band gain. I can already hear well with my Beverage system. Indeed, I can hear many DX stations that cannot copy me. Not everyone can live in a quiet location.</p><p>Since I am not in contention to win I can only compete against myself. That is, to improve my score over preceding years or to reduce the gap to the big guns on top band. I prefer to instead chase DX in the contest and do as well as I can without upsetting my life by staying awake for two nights. My objective may change when/if I improve my transmit antenna.</p><p>The short version: I can't win and the contest is long, so I decided to have fun by working DX and running NA stations at other times. Mission accomplished. <br /></p><p><b>Capabilities</b></p><p>My <a href="https://ve3vn.blogspot.com/2020/11/160-meter-shunt-fed-tower.html">transmit antenna</a> is very good but has no gain. Recently I <a href="https://ve3vn.blogspot.com/2023/11/improving-maybe-160-meter-shunt-fed.html">doubled the number of radials</a> for higher efficiency which, although it helps, is an improvement of no more than 1 db. I have little trouble working DX when conditions are cooperative. Late Friday evening when the propagation to Europe was good, I did well at running European stations.</p><p>My receive capabilities are better. With three reversible Beverages that are from 150 to 175 meters long, I can copy most anyone. I could build a vertical receive array with a higher RDF, but hearing well is not my problem. I hear better than almost everybody else hears me. Most hams have a higher local QRN level. </p><p>An imbalance between receive and transmit capabilities can be a problem. Usually it's a station running high power and unable to hear due to their local noise. We call those alligators: big mouth and small ears. I'm in the opposite situation. I something think of myself as an SWL (short wave listener) when I can't work many DX stations that I hear very well. Alligators and SWLs both have difficulty filling the log.</p><p>The only antenna work I performed in preparation for the contest was to repair an intermittent F connector on the northeast-southwest Beverage. I pulled off the twist-on connectors, removed corrosion and lightly coated the threads with dielectric grease. It was an easy job in the cold winter weather. I considered myself lucky that recent wind and ice storms didn't damage the Beverages.<br /></p><p><b>DX prospects</b></p>An important difference between a major contest like CQ WW and CQ 160 is the number of contest DXpeditions. There are many in the former and few in the latter. Don't expect to work many countries in CQ 160. That said, there is a lot of DX to be worked when propagation cooperates. This year that was mostly limited to contacts between Europe and NA. That's quite good on top band for the peak of the solar cycle. I logged 51 countries, which is pretty good for the hours I put in. The highest I saw from eastern NA was 70.<br /><p>There is an ebb and flow to propagation on 160 meters. It isn't like the HF bands. Signals from an area can rise for 10 or 30 minutes before falling back down. You need to be on at those times to work DX. Since these events are largely unpredictable, you must be diligent during the contest. I stayed up late the first night and was rewarded with lots of contacts with Europe and the west coast of NA.</p><p>Stations located far from the major global population centres have little incentive to be active in CQ 160. They can only work stations during periods of propagation enhancement. Many of those stations are in the southern hemisphere where it's summer and the atmospheric noise is very high. That's less of a hindrance in multi-band contests since you need only check 160 occasionally. For a 160 meter contest it can be very dreary indeed. </p><p>When there is propagation to those distant parts of the globe there may be no activity at all. Several times during the contest I saw weak but consistent RBN reports from a CX, yet throughout the contest I heard no stations from South America further south than Venezuela.<br /></p><p>Propagation extended towards the west and northwest to KH6 and KL7. I worked two of each but nothing farther. Japan and other east Asian stations were active but not heard here. It was the same for them except for a few of the top band big guns. Based on their reports, ZL and VK stations worked mostly western NA stations, and few of those.</p><p>I enjoyed working the DX on offer, and that's all you can ask for on 160 meters. Many times the propagation during 160 meter contests is far worse.</p><p><b>Conflict</b></p><p>With so many stations packed into a fairly narrow spectrum there is bound to be conflict. There were several examples of it during the contest. <br /></p><p>When DX conditions to Europe are marginal, we can hear each
other although QSOs are difficult. The reason is that most stations do
not hear well, either due to local noise and poor or no receive
antennas. NA and EU stations operate right on top of each other without noticing. Try to
work one of those Europeans and conflict arises. I tried a few times and
it wasn't worth the trouble, even when I did my best to avoid QRMing
the NA station when calling the DX station.</p><p>One workaround that
some stations use is to run high in the band. The idea is to be decoded
by skimmers and attract stations to QSY from the lower end of the band
where activity is greatest. It works, to a degree. One reason is that many skimmers use antennas that are poor for
receiving DX stations and fail to decode weak signals. Another is
that many of the stations drawn to the spot can't copy the weak DX
station. Of course, there are many unassisted stations that won't see the spots.<br /></p><p>Early in the contest few stations tread on the FT8 watering hole at 1840 to 1843 kHz. Over time, more and more stations went there. To avoid adding to the potential QRM I avoided calling those stations. As the rate slowed and FT8 operators abandonned the window (probably because of the QRM), I called a few of the CQers in the window. The damage had been done. </p><p>There was similar interference with phone operators (AM and SSB) during the evening hours when they are most active. Due to the different mode band widths some "sharing" can be tolerated but it is never pleasant for either operator. Conflicts of this type are common during contests and some pile ups on rare DX stations since there are no firm mode sub-bands on 160 meters. I recall tuning to 160 meters during NAQP SSB and deciding not to bother searching for DX due to the large number of phone signals.</p><p>SO2R/SO2V operators that vacate a frequency to call a station (S & P) elsewhere risk losing their run frequency. There were several times when I came across a clear frequency and heard no reply to a couple of "QRL?" requests. So I called CQ to start a run. Soon the absent station returns and resumes CQing. Who's frequency is it? Since I wasn't serious in the contest I never bothered to assert my claim to the frequency. In other circumstances I might react differently.</p><p>Now it's time to talk about signal quality. That means key clicks. When everybody is packed together, key clicks interfere with stations up to 3 or 5 kHz away. Mostly it's just annoying while at other times the interference is a problem. I wonder how many of those stations realize how poor their signals are. They are glaringly obvious on the 7610 spectrum scope. I feel a little sheepish mentioning it since my FTdx5000 is notorious
for key clicks. However, in this contest I used the far cleaner Icom
7610.</p><p><b>Prospects for improvement</b></p><p>Doing well in 160 meter contests requires more than a quiet location and good receive and transmit antennas. In a single band contest it is necessary to maintain a constant presence by running almost full time. Yet it is also necessary to search for and work stations S & P.<br /></p><p>One of the methods that the most competitive stations use to increase their score is a second receiver (SO2V). Some go so far as a second station (SO2R). If the signal of the transmitter into the second receiver is too strong -- which is almost always the case -- the second receiver is disabled while transmitting. That is highly disruptive to effective operating, especially since the primary VFO or radio should be almost always running.</p><p>The solution is a remote receive antenna. It can be far enough to allow the second receiver to perform well during transmissions, or have a notch in its pattern directed at the transmit antenna. Using a receiver with a high blocking dynamic range allow continuous reception on the second radio, often quite close to the transmit (run) frequency. When a station is found, the VFOs or antennas can be swapped to call them with only minimal interruption to the run radio. This is ordinary SO2R behaviour but with both rigs on the same band.</p><p>SO2R for 30 hours is not easy, and is made more difficult by the paucity of new stations to work during the second night. There's a lot of effort for little return. Assisted operation using human spots and skimmers (<a href="https://www.reversebeacon.net/">RBN</a>) eliminates the tedium of spinning the VFO and typing calls. Many top band operators dispense with assistance and embrace the challenge of doing all the work themselves.</p><p>I kept it simple and relaxed by operating SO1R with assistance. I felt no temptation to turn on the second VFO to call stations while I was running. SO2V isn't technically difficult if you can deal with constant interruptions due to the transmit cycle. I have no plan for a separate remote receive antenna to make SO2R/SO2V more viable on 160 meters. My only plan for improvement is to eventually phase the two big towers, as described earlier.<br /></p><p><b>Scoring equity</b></p><p>It is a rare contest where the scoring equalizes the playing field among stations in diverse locations. There are two rules in particular that skew the points awarded to a QSO:</p><ul style="text-align: left;"><li>The 5 points awarded to QSOs between US and Canadian stations favours Canadians because there are so many more Americans. US to US and Canada to Canada contacts are worth 2 points.</li><li>QSO between countries are worth 5 points while those between continents are worth 10. That rule benefits stations just beyond the continental divide. For example, south Italian islands in Africa, Cyprus, Africa islands near Europe, and north South America.</li></ul><p>The scores of Canadian stations are much higher than those of Americans with similar numbers of QSOs and multipliers. The difference is greater for African stations adjacent to Europe who typically win the overall. Of course, stations farther afield fare even worse since they can never make many contacts in a 160 meter contest. An inter-continental QSO is 10 points whether the distance is 100 km or 10,000 km.<br /></p><p> Do these scoring differences matter? Solutions exist such as the distance and power based QSO points used in the <a href="https://www.kkn.net/stew/stew_rules.html">Stew Perry top band contests</a>. In CQ 160, if you restrict comparisons between stations in the same country, region and category, the scores are comparable. But many of the contests top awards aren't awarded on that basis. I don't expect to see scoring changes anytime soon. I'd be happy to be proved wrong. I say this despite the benefit to Canadians of the extant rules.<br /></p><p>There is also the matter of hemispherical bias. A top band contest in January favours the northern hemisphere when nights are long and the atmospheric noise low. Southern hemisphere stations have short nights and high noise. Moving the contest to coincide with one of the equinoxes would improve hemispheric equality. That, too, is unlikely to change since the majority of 160 meter activity is in the north.<br /></p><p><b>Recordings</b></p><p>I'll close with an interesting development. Several stations in Europe sent me recordings of our QSOs. Recording contests is common, and not only for the top competitors for whom it may be mandatory. I suppose some enjoy doing it for whatever reasons they might have. It was interesting to hear what my signal sounds like at the other end of a 160 meter DX contact. </p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com1tag:blogger.com,1999:blog-6207999661586171874.post-12099225846059308592024-01-26T13:40:00.002-05:002024-01-26T14:14:35.004-05:00Stacking 20 Meter Yagis: 2 Long vs. 3 Short<p>Only a fraction of hams have stacked yagis. They are common in both VHF/UHF and HF big gun stations. There are still lessons about antennas to be learned for those who do not and will never deploy a stack. There is a question about stacks that I'd like to explore in this article that comes up from time to time. It may be of interest to those with and without stacks.</p><p>The question is this: which is better, <a href="https://ve3vn.blogspot.com/2019/08/stacking-scenarios-for-new-tower-15-and.html">2 long boom yagis</a> or 3 yagis with more modest boom lengths? I am going to focus my analysis on 20 meters since that is a band where <a href="https://ve3vn.blogspot.com/2018/09/challenges-of-long-boom-yagis.html">long boom yagis are very large</a> and expensive. Many contesters instead choose to stack three or more yagis with shorter booms. There are more of them in the stack but each is less difficult to build and raise. </p><p>There are advantages to using 3 smaller yagis:</p><ul style="text-align: left;"><li>More pattern possibilities by selecting combinations of 2 of the 3 yagis</li><li>It is easier to rotate the <a href="https://ve3vn.blogspot.com/2016/02/side-mounting-yagis.html">side mounted yagis</a>, offering more directions with stacking gain</li><li>The main azimuth lobe is wider, which can be a benefit for contesting <br /></li></ul><p>There are disadvantages as well. These are primarily narrower low SWR bandwidth and lower gain. Unless the ham has unlimited resources, the stacking of smaller yagis is a popular choice. </p><p>It also helps that there are suitable yagis on the used market that can be purchased inexpensively and, where needful, optimized for gain, pattern and SWR. The Hy-Gain 204BA is a common choice. The optimized version of that antenna by N6TV is popular. Performance and construction details can be found in the <i>ARRL Antenna Book</i>.<br /></p><p>I chose two long boom yagis for my 20 meter stack, and similarly for <a href="https://ve3vn.blogspot.com/2016/01/5-elements-on-15-with-found-boom.html">15</a> and <a href="https://ve3vn.blogspot.com/2021/09/building-5-element-10-meter-yagis.html">10 meter</a>s, although those are smaller antennas. I kept the expense down by designing and building them myself, and I got a lot of <a href="https://ve3vn.blogspot.com/2023/11/on-becoming-big-gun.html">satisfaction</a> from the project. Most contesters would rather buy or modify so that they can get a big signal with minimum fuss. Not everybody has the same interests and priorities.</p><p>The breadth of this article is narrow in that the baseline for comparison is my antennas. I am most interested in alternatives to what I've built and the scope for future improvement. I will not do a broad comparison of various stack configurations. That said, lessons from this brief analysis have broader application.</p><p><b>The antennas</b><br /></p><p>I will compare my <a href="https://ve3vn.blogspot.com/2019/08/stacking-scenarios-for-new-tower-15-and.html">20 meter 5-element yagis on a 41' (12.7 m) boom</a> to the N6TV 4-element yagi on a 26' (8.1 m) boom in the ARRL Antenna Book. Despite a 50% longer boom the gain of the 5-element yagi is not that much higher. Many big guns with 5-element yagis put them on a 48' boom for more gain. I chose an intermediate length boom as a compromise between performance and mechanical difficulty.<br /></p><p>There are diminishing returns as the boom get longer. Keep in mind that the boom length, not the number of elements, is the determining factor for maximum gain. Elements are added to a long boom yagi to achieve the required level of mutual coupling for maximum performance.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEinZ4jaGdYIl8rVE1q0eq8ILaUTFCIsvL3oj4-SdaPOx0k2UDfxKI0d6V8qRqwxW8iZZESu4rBof2iBYD-4TRMsYYZPBrKlfcAPnfq0eA3eQQ0vA70fjMikazmj5FMgDmGXdIKXfATrGoqXJgLFnJ4gxJXnGNtGBHLKByw0A1UCr3VH1C1NYKEhCSAebpVZ/s546/20m_4elvs5el_freespace_gain.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="276" data-original-width="546" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEinZ4jaGdYIl8rVE1q0eq8ILaUTFCIsvL3oj4-SdaPOx0k2UDfxKI0d6V8qRqwxW8iZZESu4rBof2iBYD-4TRMsYYZPBrKlfcAPnfq0eA3eQQ0vA70fjMikazmj5FMgDmGXdIKXfATrGoqXJgLFnJ4gxJXnGNtGBHLKByw0A1UCr3VH1C1NYKEhCSAebpVZ/s16000/20m_4elvs5el_freespace_gain.png" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgHQe6h4LuY7zjYpAMGsunSwzEDTPjXUM2GkSm_6ATu7pXEjKqVsF4v2EsYATE-pW26_hs1Q-ys3LvPWU7-9dVmdEy6Jt2hsS6zfaUrP7jIc-yIWr8zLv2zDnkBdYeg963eACn3-tFckYFebupEpd9uhtUt-k9ZlDGyxBWPZVrGP1jYk4A_w_EOxeXNCBl0/s878/20m_4elvs5el_100ft_az-el.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="405" data-original-width="878" height="296" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgHQe6h4LuY7zjYpAMGsunSwzEDTPjXUM2GkSm_6ATu7pXEjKqVsF4v2EsYATE-pW26_hs1Q-ys3LvPWU7-9dVmdEy6Jt2hsS6zfaUrP7jIc-yIWr8zLv2zDnkBdYeg963eACn3-tFckYFebupEpd9uhtUt-k9ZlDGyxBWPZVrGP1jYk4A_w_EOxeXNCBl0/w640-h296/20m_4elvs5el_100ft_az-el.png" width="640" /></a></div><p style="text-align: left;">The 4-element yagi is blue on the above charts. The gain difference ranges from 1.2 db at 14 MHz to 0.8 db at 14.350 MHz. The pattern comparison was done near the top of the band where the gain difference is small. Although the gain advantage for the 5-element yagi drops at the high end, the SWR remains very good while that of the smaller yagi rises to over 2. </p><p style="text-align: left;">For a 5-element yagi on a 48' (14.6 m) boom the gain is higher by 0.5 db at 14 MHz and rises to 1 db at 14.35 MHz. At the time I designed my yagis I decided not to make the boom longer to keep the weight, cost and maintenance to within bounds that I was comfortable with. I will continue the analysis with my antennas since that is my primary interest. Tack on the extra gain if your interest is a 48' boom<br /></p><p style="text-align: left;">These comparisons bring up a common point of contention: does 1 db make a difference? Yes, it does, though perhaps not in the way most think about it. Except for weak <a href="https://ve3vn.blogspot.com/2016/02/propagation-noise-and-qrp.html">signals riding the noise level</a>, you will benefit little from the difference on receive. It is different at the other end of the QSO. More stations will hear you because your signal is more competitive with their QRN and their QRM. You don't often notice that for daily operating, but it makes a difference in DX pile ups and during contests. A seemingly small signal improvement can improve contest scores.</p><p style="text-align: left;"><b>Comparison of 2 × 5-element and 3 × 4-element stacks </b></p><p style="text-align: left;">For model simplicity, the yagis are directly driven with a source placed at feed point of each driven element. There are no matching networks since there is no model penalty for an impedance mismatch and the patterns are unaffected. All yagis experience mutual coupling with the others, which is unavoidable and the reason that stack gain is not the 3 db that one might expect.<br /></p><p style="text-align: left;"></p><p style="text-align: left;">Now that we've set the baseline, let's move on to the comparisons. We know at the outset that stack gain is nominally 3 db. It can vary ±1 db or so due to yagi separation and height, and there may be effects of unequal power division when the impedances of the yagis are different. I think most will agree that 2 to 4 db does make a difference in on air results. In my experience the impact can be surprisingly large.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhj3FWD3_2gLd2yA2Q6n9zmDzYKbVTOD1wcpyaN8EpFceAIqTxzAl8FSZZy55vEbuTRVSvINZvoQXm79kWYVoedKX5XQU3ZbQXAHJgbj33auSCE17cEKzehC7YxoKGkndiw-PU7dhQxedJbuwc3haz2gHYPK31XWMlsFDhbZpbiR8g1_IpcyWSx7Q9OUzla/s618/20m_4elvs5el_stacks_view.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="343" data-original-width="618" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhj3FWD3_2gLd2yA2Q6n9zmDzYKbVTOD1wcpyaN8EpFceAIqTxzAl8FSZZy55vEbuTRVSvINZvoQXm79kWYVoedKX5XQU3ZbQXAHJgbj33auSCE17cEKzehC7YxoKGkndiw-PU7dhQxedJbuwc3haz2gHYPK31XWMlsFDhbZpbiR8g1_IpcyWSx7Q9OUzla/s16000/20m_4elvs5el_stacks_view.png" /></a></div><p></p><p style="text-align: left;">The heights of the 20 meter 5-element yagis are 140' (42.7 m) and 70'
(21.3 m), which is approximately where I have them on my tower. I placed
the upper and lower optimized 4-element yagis at the same heights and
inserted a third midway at 105' (32.0 m). The one in the middle is
approximately at the height of my lower 15 meter yagi. </p><p style="text-align: left;">I believe that this a fair
comparison. A third 5-element yagi does not easily "fit" because it's too close to the existing yagis. I exclude that case for now, but I will return to it later.
Hence the comparison of my 5-element stack to a 3-stack comprised of the shorter 4-element yagis.</p><p></p><p style="text-align: left;"></p><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-X7ocnIcrJNDihC5RMZItLj01HE1xRbhIfFzqZRe8PTyPa0RxxEhMNq5WvMuwNR2PBsvJwdn3aIzc3V47IsbSqtJD_q4WsZEFvW0273Yljh928yT58yaQKQ4p5py5lT33zS9R5BLYpzkhprBedXh1OCLbMp9mtTuClnL2eL6oZ1bJPoiuCMxK91oMiLLn/s950/20m_4elvs5el_stacks_elev.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="392" data-original-width="950" height="264" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-X7ocnIcrJNDihC5RMZItLj01HE1xRbhIfFzqZRe8PTyPa0RxxEhMNq5WvMuwNR2PBsvJwdn3aIzc3V47IsbSqtJD_q4WsZEFvW0273Yljh928yT58yaQKQ4p5py5lT33zS9R5BLYpzkhprBedXh1OCLbMp9mtTuClnL2eL6oZ1bJPoiuCMxK91oMiLLn/w640-h264/20m_4elvs5el_stacks_elev.png" width="640" /></a></div><p></p><p style="text-align: left;">There are several interesting points that can be seen in the elevation plots:</p><ul style="text-align: left;"><li style="text-align: left;">The gains of the full stacks are nearly equal.</li><li style="text-align: left;">The 5-element yagi, as a stack and as individual antennas, have poor coverage of elevation angles between about 30° and 35°. There are no gaps with the 4-element yagis.</li><li style="text-align: left;">Other than the full stack, the 5-element yagis are individually always better. That is perhaps most important for the upper yagi on long haul DX paths with the lowest elevation angles.</li></ul><p>The 4-element stack does pretty well in the comparison. The azimuth pattern (see above) is broader and that can be an asset during contests where you want to reach the maximum number of stations while running. However, the beam width difference is small. Vertical stacking narrows the elevation lobes but not the azimuth lobes.</p><p>Although you need 3 yagis instead of 2, the mechanical advantages of the smaller 4-element yagis is enticing. I know many contesters that have gone that route. </p><p><b>Additional combinations of the 4-element yagis</b></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiWXVPRgA_ZP0mHXkGbYYGVrnr_b9dfNwFEudjPYoL2bpE4tSnr9y4yGCrpnaDYHkRXcJhAu9szRFxmbgiHSzDoPknu59YSWCeWk0ydVCuhAt8IJtIa1qjX6SWKOqtFArA2ghw-xx_OoIQ_B-ueNpcPCTsReR2pos4a6RT1AoTcYIzQV65jYn45VhXyQ7YX/s509/20m_4el_stack_u-m-l-2x_elev.png" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="466" data-original-width="509" height="366" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiWXVPRgA_ZP0mHXkGbYYGVrnr_b9dfNwFEudjPYoL2bpE4tSnr9y4yGCrpnaDYHkRXcJhAu9szRFxmbgiHSzDoPknu59YSWCeWk0ydVCuhAt8IJtIa1qjX6SWKOqtFArA2ghw-xx_OoIQ_B-ueNpcPCTsReR2pos4a6RT1AoTcYIzQV65jYn45VhXyQ7YX/w400-h366/20m_4el_stack_u-m-l-2x_elev.png" width="400" /></a></div><p style="text-align: left;">There are 3 combinations for the 4-element yagis (not including BOP -- both out of phase) that are not available with the 5-element yagis. Those are the three combinations of two yagis.</p><p></p><ul style="text-align: left;"><li>Upper + Middle</li><li>Middle + Lower</li><li>Upper + Lower</li></ul><p>We now have 7 total selection possibilities. The question is whether so many is beneficial. Compare these elevation plots with those above. The full 3-stack is the primary (black) trace.<br /></p><div><p style="text-align: left;">It isn't surprising that the elevation pattern of the last combination -- upper + lower -- looks very similar to that of the 5-element stack. The only significant difference is that the gain is lower by about 1.3 db. That closely matches the difference between single 4-element and 5-element yagis.</p><p style="text-align: left;">The other combinations of two yagis are more interesting. Both do well in the lowest elevation angle lobe, with only a small difference in the elevation angle where they peak. The gains are down only by about 1 to 1.5 db from the full 3-stack. This is about what to expect in general between 2 vs 3 yagis in a stack; the difference between 1 and 2 yagis is of course approximately 3 db. There are diminishing returns. You'd need a fourth yagi to get close to 3 db more gain than a stack with 2 yagis.</p><p style="text-align: left;">Another advantage of the upper-middle and middle-lower combinations is that the middle elevations are well covered. The individual yagis in a stack of 4-element yagis achieve that as well (see above) but now we do it with increased gain. The high angle radiation is also reduced in comparison to the upper-lower combination. That may be useful if you don't have a separate low yagi or you wish to avoid BOP (both out of phase) configurations. The latter adds complexity to the stack switch. </p><p style="text-align: left;"><b>Challenges and benefits<br /></b></p><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiNDSNz0wQGCz45RIkJ5zT46TSU_gqMhc5XhpEcs3nbMgtVijlTfDG7GiffdExzc0Bet6x-8i__uR6whW-9lChnANlqop2hZLcrn4q0xOow3EdYsfEvsvNptRq6DzQrCjnKPg3DDbsQsLAB7N_Fbq0btl6_ur2Bb75zhuNbKB9af-W4BZwlaU5rOSAQLskV/s1919/SM%20RC.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="1033" data-original-width="1919" height="172" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiNDSNz0wQGCz45RIkJ5zT46TSU_gqMhc5XhpEcs3nbMgtVijlTfDG7GiffdExzc0Bet6x-8i__uR6whW-9lChnANlqop2hZLcrn4q0xOow3EdYsfEvsvNptRq6DzQrCjnKPg3DDbsQsLAB7N_Fbq0btl6_ur2Bb75zhuNbKB9af-W4BZwlaU5rOSAQLskV/s320/SM%20RC.jpg" width="320" /></a></div><p style="text-align: left;">The many combinations of a stack with three yagis add complexity on the tower and in the shack. There are 7 combinations compared to 3 with a two yagi stack, not counting BOP. At right is an example of a controller for a 3-stack system sold by <a href="https://www.arraysolutions.com/stackmatch-general-information">Array Solutions</a>.</p><p></p><p style="text-align: left;">Impedance matching is, perhaps surprisingly, less of a problem. There are several stack switches for three yagis that employ one network for feeding two or three of the yagis; the network is bypassed when selecting an individual yagi. </p><p style="text-align: left;">A common solution is a TLT (transmission line transformer) wound on a large (2.4") ferrite toroid. There is a low insertion loss design whereby the transformation ratio is approximately 2.25. The net SWR isn't perfect but it is still pretty good for both cases. For a 50 + j0 Ω load, the SWR would be 1.1 for two yagis and 1.3 for three yagis. Since no yagi has a perfectly flat SWR, the mismatch due to the TLT may be dominated by antenna's SWR. That is, you might not notice it most of the time.<br /></p><p style="text-align: left;">I could do the same with my <a href="https://ve3vn.blogspot.com/2020/08/l-network-stack-switch-for-20-meters.html">home brew stack switches</a> by altering transformation ratio of the L-network. It is also possible to switch a capacitor by relay to improve the match when selecting either two or three yagis. My stack switches are single band only while the TLT network is broadband, typically covering 40 to 10 meters. You need the latter for multi-band antennas such as tri-band yagis.</p><p style="text-align: left;"><b>What I've learned</b></p><p style="text-align: left;">There are no big surprises in this analysis and comparison, nor did I expect any. The benefit comes from being able to put numbers to the scenarios rather than make broad assumptions. It was a useful exercise. I'll briefly list several of my thoughts from this modelling exercise:</p><ul style="text-align: left;"><li style="text-align: left;">A stack of 4-element yagis works very well. The gain of a 3-stack compares favourably to my 2-stack of 5-element long boom yagis.</li><li style="text-align: left;">There are more stacking options with 3 yagis. You can split the stack to point the rotatable yagis one direction and still have a 2-stack in another. Smaller yagis are far easier to rotate on a side mounted swing arm (or ring rotator) than my 5-element yagis.</li><li style="text-align: left;">When the 4-element stack is split, typically the upper yagi would be used for a long haul path such as Asia while the middle and lower yagis can be pointed to Europe. The gain to Europe of this combination is about 1.5 to 2 db lower than the full 4-element stack. That can be a reasonable sacrifice during contests if done only occasionally. It is superior to the choices I now have.</li><li style="text-align: left;">The many combinations that are possible with a 3-stack entail complexity. During a contest there is no time to play with all of the possibilities or to explain it to guest operators. There is also little advantage since the elevation angle and other propagation factors vary from one QSO to the next. They additional combinations may be have greater value for DXers.</li></ul><p>One way to reduce the complexity of the stack is to permanently bond two of the 4-element yagis. If I were to do it, I would bond the middle and lower yagis. That entails bringing the transmission lines for those yagis to a <a href="https://ve3vn.blogspot.com/2020/07/phasing-stacked-yagis-with-coax.html">common point at 0° phase shift (in phase)</a> and feeding them in parallel with a network to transform 25 Ω to 50 Ω. Coax is run from there to the stack switch, also with a 0° phase shift, between the bottom pair and the upper yagi.</p><p>The stack switch can be same one as for a 2-stack since its operation is identical. When you select the "lower" yagi you are actually selecting a 2-stack.<br /></p><p>I have no intention of replacing my 5-element yagis. They are excellent antennas that do wonders when stacked. However the stack only works towards Europe because the lower yagi is fixed. It would be nice to have another yagi in between so that there can a middle-lower 2-stack to Europe when the upper yagi is pointed elsewhere.<br /></p><p style="text-align: left;"><b>Possibilities</b></p><p>I do not want another 5-element 20 meter yagi on the tower for several reasons. It also fits poorly since the separation between yagis would be less than the boom length. That's a <a href="https://ve3vn.blogspot.com/2019/08/stacking-scenarios-for-new-tower-15-and.html">pretty good heuristic</a> for spacing the yagis in a stack since it addresses the bulk of the mutual coupling issues. A side mounted 5-element yagi is difficult and expensive to rotate due to its <a href="https://ve3vn.blogspot.com/2019/09/weighing-yagis.html">weight and wind load</a>. I won't even try.</p><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg3Y7IDs845tbr7qAICffPAkCV_VJFlNH9XevasHjPkiDAeE9J3ho02saMLZCmL3XnozUsdu9Vjf6FXQWXiQ2oRyI6y1p_FObeqLnx2713NKUYtG4Yx6_f3vnx6jvJq1TNtxO34Vr2hNhE6vbTdgaeRRqa6dZFBtcHcmf_Wmn0eipZ5jAYWyC1mWHg-Pz7Q/s784/20m_5el_3x_stack_elev.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="394" data-original-width="784" height="322" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg3Y7IDs845tbr7qAICffPAkCV_VJFlNH9XevasHjPkiDAeE9J3ho02saMLZCmL3XnozUsdu9Vjf6FXQWXiQ2oRyI6y1p_FObeqLnx2713NKUYtG4Yx6_f3vnx6jvJq1TNtxO34Vr2hNhE6vbTdgaeRRqa6dZFBtcHcmf_Wmn0eipZ5jAYWyC1mWHg-Pz7Q/w640-h322/20m_5el_3x_stack_elev.png" width="640" /></a></div><p style="text-align: left;">This is what it looks like by the numbers. The gain of the three 5-element yagis is only about 0.6 db better than my existing two yagi stack. Even if that small boost is gain is acceptable, notice that the gain for the upper-lower combination (middle yagi not fed) is significantly reduced relative to my existing stack. Gain is compromised by interactions among the yagis -- they're too close together. The combinations of two yagis are, like the 4-element stack, equally useful, though gain is limited by those interactions.</p><p></p><p style="text-align: left;">There is another possibility: place a small yagi in the middle. The separation between yagis is greater than the small yagi's boom length though still less than the 5-element yagi boom length. Since the 4-element yagi is centred on the tower, the driven element is offset from that of its larger cousins. That can be compensated by a delay line to the middle yagi -- it is "ahead" of the others.</p><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6L244W6j_xZpD2lbO6jMSzm6UkyG-NISJFxYGAkJ_jvDp3T7-ZKmsZ0jxpfcgy0tv8cZcnDwzGMTk0YcRXmUNPu2iH9FABPuae3savN6E0xdif0XPc8HX6q0JDeu_30-ROlTpVtNZtEBC_2gZqRsaRAdLdRu3immE_t0204qD8_JDe2uwgFLZBOfUOZLR/s770/20m_5el_2x_and_4el_3stack_elev.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="396" data-original-width="770" height="330" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6L244W6j_xZpD2lbO6jMSzm6UkyG-NISJFxYGAkJ_jvDp3T7-ZKmsZ0jxpfcgy0tv8cZcnDwzGMTk0YcRXmUNPu2iH9FABPuae3savN6E0xdif0XPc8HX6q0JDeu_30-ROlTpVtNZtEBC_2gZqRsaRAdLdRu3immE_t0204qD8_JDe2uwgFLZBOfUOZLR/w640-h330/20m_5el_2x_and_4el_3stack_elev.png" width="640" /></a></div><p style="text-align: left;">The optimum delay line was found in the model to be 40°. That is larger than the expected 36° due to the 83" (211 cm) offset of the driven element. Mutual coupling is once again the culprit. The length of the delay line will also be sensitive to the matching network at the feed point, such as a gamma or beta match, since they will impose a different phase shift (reactance) compared to the larger yagis. To avoid model complexity, I included sources for each yagi without concern for impedance mismatches. You can do that in a model but not for a real antenna.<br /></p><p></p><p style="text-align: left;">Even that doesn't help us. The gain of the 3-stack is almost exactly the same as my existing 2-stack of 5-element yagis. The degradation due to mutual coupling becomes very apparent when the middle 4-element yagi isn't fed. The currents induced on the inactive antenna elements isn't large but more than enough to disturb the stack's pattern. The currents can be inspected in the model.<br /></p><p style="text-align: left;">Gain is about 1.5 db worse than if the 4-element yagi were not on the tower. The upper-middle and middle-lower combinations certainly have utility but for the reduced gain. The middle-lower combination can have higher gain when the upper yagi is rotated to a different direction.</p><p style="text-align: left;">If you are enamoured of the additional combinations made possible with a 3-stack, you must either use 4-element yagis or increase the tower height to achieve wider spacing of the 5-element yagis. A taller tower is not in my future!<br /></p><p style="text-align: left;">This is useful information. While I have no serious plan to redo the 5-element 20 meter stack, the alternatives are worth pondering. If a 20 meter stack is in your future, detailed modelling should be done <i>before </i>planting a big tower. <a href="https://www.n1fd.org/2021/11/07/hfta-intro/">HFTA</a> is another useful tool to optimize stack configurations for the local terrain before beginning construction.</p></div>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com0tag:blogger.com,1999:blog-6207999661586171874.post-8043135299488873932024-01-21T10:28:00.001-05:002024-01-21T10:29:04.892-05:00The Intensity of NAQP<p>Although I call myself a contester, there are times when I don't enjoy it. Most of what I dislike are intensity and the duration. <a href="https://ncjweb.com/naqp/">NAQP (North American QSO Party)</a> has intensity. At 10 hours of operating time it is at least brief. I can survive it even if I'm not always having fun. Despite that, it's a superb opportunity for honing one's contest skills.</p><p>The power limit of 100 watts tends to even out the competition. Modest stations can do well in these contests if the operator is skilled. The playing field is not truly level since antennas, location and propagation play large roles. The latter is somewhat balanced by propagation that favours western stations on the high bands and eastern stations on the low bands.</p><p>Despite the pressure I put on myself to do well, I dove in at the opening bell and did my best. As we'll see, I did better than in previous NAQP CW contests. That's promising.</p><p>This article might not be of interest if you're not a contester. That's okay. Even if no one cares, I benefit from writing the article since it helps me to think about what does and doesn't work, and then consider what I might do differently in future contests.<br /></p><p><b>Team competition</b></p><p>The team competition isn't taken too seriously by most participants. You can tell just by scanning the list of irreverent team names. <a href="http://va3cco.com/">CCO (Contest Club Ontario)</a> enters teams in NAQP according to member interest and participation. </p><p>Despite not being a top-tier competitor, I do well enough that I am usually included in the CCO #1 team. That alone puts me in under pressure to do well since I get put on the same team as two WRTC gold medallists (VE3DZ and VE3EJ). I know them both and I'm sure they would have a good chuckle to hear that. The pressure comes from within, not from my fellow team members.</p><p>A little pressure to perform well is good. In past years the pressure of friendly competition made me a better runner and cyclist, whether it's a group sprint to the top of a mountain or not letting a friend pull ahead of me during a half marathon.</p><p>One peculiarity about the team competition in NAQP is that mixes assisted and non-assisted operators. Obviously teams with more assisted operators will score higher. Our team had at least two in the assisted class.<br /></p><p><b>Practice</b></p><p>I don't practice SO2R very much, and 2BSIQ even less. You must
do it in NAQP to have a competitive score. There are always stations to
work so if you keep to a single "stream" you cannot be competitive. Of course, none of this matters
for those in the contest just for fun. </p><p>Many top contesters train with MorseRunner, RUFZ and other training aids leading up to major contests. I've tried offline training and hated it, so I no longer bother. Performing well is nice but it is not imperative. I get my practice on air. I know other (and better) contesters that do the same and for the same reasons. It's "real" radiosport. <br /></p><p>I pick second tier contests in which I have no interest in placing well and that have enough activity to enable long runs and that have many stations and multipliers to hunt. For NAQP my practice took place in the RAC winter contest. I usually enter it just to hand out 10-point contacts to participants. This time I did it SO2R with a lot of 2BSIQ, unassisted and running 100 watts. <br /></p><p>SO2R and 2BSIQ are more difficult in RAC, CQ WPX and other contests that include a serial number in the exchange. You cannot rely on the <a href="https://ve3vn.blogspot.com/2020/01/call-history.html">call history</a> file for the contest. In contests like NAQP with fixed exchanges, all I do for most contacts is listen to ensure the name and state match the pre-filled data, and only type when they do not. It saves mental and physical energy when operating two radios. It's more stressful with serial numbers because you must listen and copy the unique exchange. That makes for good practice.<br /></p><p><b>2BSIQ technique</b></p><p>For SO2R, I use N1MM+, two keyboards and the SO2R Mini for controlling radio audio. It's what I'm use to but there are many alternatives. I am definitely a fan of <a href="https://ve3vn.blogspot.com/2019/11/thoughts-on-two-keyboard-so2r.html">two keyboards</a> since I find it easier to mentally associate typing with the radio. When I need to focus on the audio of one radio, the "~" key in N1MM+ signals the <a href="http://nn1c.org/so2r/">SO2R Mini</a> via its OTRSP interface. There are <a href="https://ve3vn.blogspot.com/2019/01/bare-bones-so2r.html">simpler</a> and more complex (and expensive) products to manage receiver audio. </p><p>N1MM+ has a software interlock so that you never transmit on both radios at the same time. That makes it easy to comply with the rules. For this contest I was powering two rigs from a single DC power supply. Since there is never a two transmitter load on the power supply you can get by with one 25 amp supply for both rigs<br /></p><p>Synchronizing the QSOs on two radios can be difficult. The other operator may delay their transmission, send very fast or very slow, repeat the exchange, fail to respond the first time, send superfluous information (e.g. their call, again, or my call before the exchange), and so on. You must be prepared for surprises during every QSO.</p><p>There are many techniques for keeping the QSOs in sync. I am still learning but I know enough to do reasonably well. Sure, I flub a lot as well. It's important not to become embarrassed or despondent, and slink back to SO1R with head bowed. Keep at it and focus on getting back in sync.</p><p>Consider these alternative CQ messages (you can substitute "TEST" for "NA" in other contests):</p><ol style="text-align: left;"><li><b>VE3VN NA</b></li><li><b>NA VE3VN</b></li></ol><p>Which is better? In some circles it is actually a point of contention. For SO2R, in my opinion, you ought to use the second. When the station you are in contact with on the other radio transmit longer than the CQ on the other radio it is a simple matter to tap F4 (or other function key depending on the logging software) to repeat your call to extend the CQ. You can't do that in the first case. </p><p>I will also interrupt a CQ when I must transmit on the other radio, usually when I'm S & P on it, so that the other station doesn't think I've disappeared. Interrupting a CQ has a low cost while delaying an S & P transmission has a relatively high cost.<br /></p><p>There are many more tricks that help to sync and re-sync the QSOs. Since this is not an article strictly about SO2R, and I'm not expert enough to be giving advice, I won't delve deeper. You'll figure out most of it on your own, eventually, if you keep at it. The better you get the less stressful it becomes. Your scores will increase and that will motivate you to stick with it. Always keep in mind that when you make SO2R flubs you are still providing a <a href="https://ve3vn.blogspot.com/2021/01/so2r-benefits-everyone.html">benefit for all participants</a>.<br /></p><p><b>Agility</b></p><p>In many contests, when you run you tend to do so for a long time. That is unusual in NAQP except for those with big signals from a rare multiplier. Most stations are hopping from band to band, so that when a run slows it is best to switch as well. You must both run and hunt, switch frequently and often hop from band to band. </p><p>If you stick to running for too long, you will not work others that are running. The opposite is true for S & P. <i>For every QSO</i>, one of the stations is running and the other is hunting. It has to be that way. For those operating SO2R, at least one of the radios should be running. Dual S & P is more difficult than 2BSIQ since you often need to copy stations on both radios most of the time. That's a rare talent.<br /></p><p>I am less agile than I ought to be. I stick with runs longer than I should, whether the rare drops or the rate remains high. The former case should be obviously true. The latter may be puzzling. By running for too long you miss activity and multipliers on other bands, and that will hurt your score no matter how good the run. Stop the run and hunt multipliers or work other bands, especially 10 and 15 meters, when they're hot. When you return to the band where you had been running. the rate will soon resume.</p><p>To be agile you must be attentive to propagation and hunt stations at high speed. If you are assisted, take advantage of that to rapidly work through the available multipliers and then other stations. But always do it while running on the other radio.</p><p>I was not as attentive to the agility practiced by others.
When I had difficulty working a multiplier due to many callers, I would
quickly move on and try to work them later. Often I delayed for too long and
the station was no longer running -- they're practicing agility! That cost me multipliers. In many
contests they stick around for longer, but not in NAQP. </p><p>I have enough antennas that I don't rotate the yagis during the contest. I set them up before the contest begins, typically pointed south, southwest and west on the high bands. For the limited number of multipliers to the east I rely on backscatter or the yagis' minor lobes. On 80, the inverted vee is used for nearby stations and the vertical yagi to reach the Caribbean and west coast. On 160 meters I mostly receive on the southwest Beverage, and switch to other directions when necessary. All switching was done with mouse clicks using my station automation software.<br /></p><p><b>High bands vs low bands</b></p><p>VE and W population is higher in the eastern half of the continent. That gives an advantage to western stations on the high bands and to eastern stations on the low bands. The high bands were so good this year that eastern stations delayed moving to 40 meters until well after sunset. In previous years there was lots of activity by late afternoon.</p><p>A common tactic of many of us in the east is to take off times during daylight. That leaves more time to work the low bands late into the evening. I took two 30 minute off times so that I could be active until midnight (0500Z). The rate was still high when I had to quit so I may have benefitted from more off time early in the contest.</p><p>The typical approach is to sweep up as many multipliers as possible on 10 and 15 meters, work as many other stations as we can and then move lower. 20 meters was my best band in this contest rather than 40 meters. Runs were ineffective on 10 and only intermittently on 15 meters, but 20 meters was very good until well into the evening. I failed to effectively use my time on 10 and 15 meters by trying to generate runs that never materialized. I should have hopped among the high bands more often and targetted multipliers.</p><p>The low bands were terrific as well, but only after stations moved down. It was pretty easy to work out to the west coast on 80 meters, and even on 40 meters well before their sunset. Later in the evening the same occurred on 160 meters. Had I been able to operate longer my multiplier count on 160 would been higher.<br /></p><p><b>Multipliers vs QSOs</b></p><p>There are 60 to 70 multipliers available to work per band in any given NAQP contest. Not all states (50), provinces/territories (13) and other North American countries are active. That adds up to almost 400 multipliers that can be found across all 6 contest bands. Propagation limits your ability to reach the maximum due to skip zones or a low MUF on the high bands, and distance on the lowest bands.<br /></p><p>The ratio of contacts to multipliers in NAQP is lower than in many other contests. In this contest my ratio was 4.8. It can be below 4 for those using assistance. The ratio is higher for the those with the highest score since they run out of multipliers to work. Look at the claimed scores at <a href="https://www.3830scores.com/">3830</a> or the <a href="https://ncjweb.com/naqp/">results</a> of past contests.<br /></p><p>A friend (who is a far better contester than I am) recently
told me that he did an experiment in a previous NAQP. He operated 2BSIQ
close to 100% of the contest. The number of contacts was higher than
usual but his multipliers were lower. That may be due to stations in
rare sections doing so well by running that they stick with it. A VE3 has to be more agile.</p><p><b>Getting fills</b></p><p>I had a peculiar problem in this contest that I haven't seen to the same extent in others. When I would ask for a fill, such as "name?", there was often silence or they'd send their call again. It took two or three tries to get the desired fill.</p><p>There was an even worse problem. In most cases when I copied a partial call, I would send the partial back one or two times. That usually worked well. Several experienced contesters would reply with only the part I was missing, whether the prefix or the suffix. That also worked well. The trouble came when I replied with the partial (or incorrect) call followed by my exchange. This is a common technique to save time and have both of us move on to the next QSO more quickly.</p><p>Few would correct an incorrect call. They either didn't care or didn't notice, though I am hoping it was the latter. Similarly, many did not provide a full call in response to a partial. As long as I sent my exchange they would reply with only their exchange. When I would repeat their call appended with a "?" or ask "CL?" or "CALL?" there would be silence or they'd repeat their name or the full exchange. In a few cases this went on several times. I don't understand it.</p><p>When all I received was silence after a few tries, I had to assume they'd left the frequency. I'd send "NIL" or nothing at all, and erase the incomplete QSO. I can understand why many contesters will not send their exchange until they've received the full correct call of the other station. I might have to start doing the same.<br /></p><p><b>Holding a run frequency</b></p><p>I was surprised by how many times other stations would jump onto my run frequency and start CQ'ing. No "QRL?" or any announcement of their presence preceded a rapid succession of CQ's. I've never seen this happen so much in major contests like CQ WW. It happened to me more than a dozen times in this NAQP.</p><p>In about half the cases the station realized their error and vanished. The rest persisted. Having a fight over the frequency only wastes time so I take action. A small QSY of 50 to 100 Hz often solves the conflict. In other cases I find another run frequency, or I switch to S & P or try another band, depending on where I think I'll be most effective.</p><p>I note their call signs, and many are well known contesters. In several cases they would call me a few minutes later when they, too, quit running. It was funny in a way. All you can (or should) do is shrug your shoulders and move on. Don't let incidents like these derail you from your primary objective of scoring well.</p><p>Another way of putting it: <i>"Contesting means never having to say you're sorry."</i><br /></p><b>Errors, call history and spots</b><p>In December I contacted the keeper of the <a href="http://supercheckpartial.com/">SCP (super check partial)</a> database (W9KKN). I requested that "VE3UN" be deleted from SCP. It's a valid call but not one active in contests. After investigation he deleted it. While I can't stop others from confusing U and V, at least there will be a "?" next to the wrong call rather than a check mark. Busted calls get into SCP because multiple contesters make the same copying error.</p><p>It did no good in NAQP. My call was regularly busted as VE3UN. I suppose that it's <a href="https://ve3vn.blogspot.com/2019/02/dealing-with-dits.html">all those dits</a>. Not everyone regularly updates their copy of the SCP database or it be in the <a href="https://ve3vn.blogspot.com/2020/01/call-history.html">call history file</a> they're using. It's also possible that they ignore or fail to notice the "?". Once they log the wrong call, it will show up as a valid option when they hear me on other bands. Assisted operators often believe spots and fail to listen. </p><p>There is little more that I can do to avoid the inconvenience of being called by those I've already worked; I already send CW slower than most to help others. For the few that repeat my (incorrect) call before their exchange, I try to correct them. Even then many don't listen. I may be among the first to apply if we convince our regulator to issue contest friendly call signs as in done in many countries.<br /></p><p>I am responsible for many of my own errors. I have yet to achieve an error rate below 1% when operating SO2R, and it is higher when also doing 2BSIQ. That isn't surprising. All I can do is practice more. I rely on call history to save unnecessary typing since that distracts me from successfully managing two QSOs. It is imperative to listen at all times since the call history may have no pre-fill. Names and locations are also frequently different. Hams move (and keep the same call sign in the US), alter their names slightly (e.g. ROBERT vs. ROB) or honour a recent silent key by using their name.</p><p>Too many don't listen and simply accept the pre-fill. I do listen and yet I still make mistakes. When uncertain or the station is weak, I will route that rig's audio to both ears for better copy, even when that means I miss critical info on the other rig. I can catch up and re-sync within 10 to 15 seconds. It's worth the effort. It isn't enough to have a high rate and multiplier count if you lose them after log checking and are docked an additional penalty.</p><p>Don't be lazy. Take the time to listen carefully and copy accurately. Your contest results will immediately improve. If you need CW practice to do it well, then put in the practice time. This applies to everyone, not only those operating SO2R.<br /></p><p><b>How I did</b></p><p>Once I overcame the initial shock of diving into SO2R and 2BSIQ during the first few minutes of the contest, I settled down and did pretty well. I made mistakes, but I have enough experience to deal with them and get back on track.</p><p>I was unhappy with my rate over the first half of the contest and wondered whether I could equal previous scores. That changed as activity moved to the low bands. The rate increased and with the great conditions the multipliers filled the log. As usually happens, running provided the majority of the multipliers. Occasional spins of the VFO are used to hunt down the rest.</p><p>My raw results were 1234 contacts and 258 multipliers. That is a little over 100 contacts and 30 multipliers less than the typical top contester in this region in the same SOAB LP (unassisted) category. The best do even better than that.</p><p>Since no two years are the same with respect to propagation conditions and activity, the real improvement is seen in the rankings. I've definitely moved higher. Compared to the previous two years, my raw numbers are improved by 10% to 15%. That is mostly due to the increased time I spent doing 2BSIQ.<br /></p><p><b>Looking forward</b><br /></p><p>I don't know how much better I can do when I am unwilling to practice more to improve my ability with 2BSIQ. It would be enough to improve my accuracy and operating strategy. I have no ambition to climb to the top of the single op standings in NAQP or any other contest. </p><p>Somewhere on that path there is a fuzzy boundary between the fun of challenging and improving myself, and aggravation. I won't cross that line.</p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com2tag:blogger.com,1999:blog-6207999661586171874.post-2780056423748250492024-01-10T21:44:00.003-05:002024-01-10T21:45:37.164-05:00Reversible Short Heliax Beverage Antenna<p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjdq7oi9ffQeT1imeP0ETRpEsPWGXWkIeu0RgXCxu_gutsi-BmjO06O2zl7pXLB-4BzpeQGfTCcSFnmWaKN4jq-t3V1SyCqKpu-3R6enCn4-eBKGDavuadoU8I3hRwi1UG2_NWJsIUcX4Oe1z6k2DcB_tIBqYCp5jvvl8f-f33wJTyOjZso20NunJnRYXPm/s600/ldf4-3_40m_sweep.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="532" data-original-width="600" height="284" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjdq7oi9ffQeT1imeP0ETRpEsPWGXWkIeu0RgXCxu_gutsi-BmjO06O2zl7pXLB-4BzpeQGfTCcSFnmWaKN4jq-t3V1SyCqKpu-3R6enCn4-eBKGDavuadoU8I3hRwi1UG2_NWJsIUcX4Oe1z6k2DcB_tIBqYCp5jvvl8f-f33wJTyOjZso20NunJnRYXPm/s320/ldf4-3_40m_sweep.jpg" width="320" /></a></div><p style="text-align: left;">I have a lot of scrap coax. What to do with it? Sure, I could throw it out but most of it still works pretty well at low frequencies even though a full spectrum sweep can look especially ugly. I persist in trying to come up with a use for it all. There are hundreds of meters of the stuff.</p><p></p><p>At left is an SWR plot of a <a href="https://ve3vn.blogspot.com/2015/09/for-future-consideration-transmission.html">40-year old 40 meter length of LDF4</a> terminated with 50 Ω. It has seen some rough handling over the years. I have 3 of these rolls in my scrap pile. They take space that I'd like to reclaim, but I haven't been able to talk myself into hauling them to the local landfill for disposal.</p><p><b>The plan</b></p><p>I would like a second set of receive antennas for multi-op contests. The existing <a href="https://ve3vn.blogspot.com/2020/05/beverage-remote-switch.html">6-direction Beverage system</a> can only be used by one station at a time since only one of the 6 directions can be selected. It can be fed to both stations if the operators are happy to use the same direction, but that's unreasonable. All I could do for the recent CQ WW contests was to switch the system to one station or the other. The one without had to make do. </p><p>That isn't so terrible since the <a href="https://ve3vn.blogspot.com/2019/11/80-meter-vertical-yagi-completed.html">80 meter yagi</a> provides <a href="https://ve3vn.blogspot.com/2019/12/performance-of-80-meter-3-element.html">pretty good RDF</a> (receive directivity factor) on receive. Unfortunately the yagi only functions between 3500 and 3650 kHz. That isn't enough for a phone contest. Extending the yagi's range to 3800 kHz may be done this year, but is more likely to be delayed until 2025.<br /></p><p>I have a need and I have a lot of junk coax. I decided to use the coax to make a reversible short Beverage pointing east and west. It's short so that the azimuth pattern is broad, close to 90° in each direction, which covers half the compass, and with a low but useful RDF -- I can add a south Beverage or other small directional receive antenna later. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgAcP2CXez1cfF1imw5HPTBWAgGQXVIXUMGmCFbmS1Hbved2X9Lmn6_ATfod5A4niUyAwfc6yrU2xCPliLVpFvEMdZwvqZd02CZJuT09HROTpDzqtbzfIAbOhP_IDiT8HcE6zDi9BJ53ANsPPJDmvwkIIRroSzL0ihRKnCZ-okZS-o-OCETlKuATmKh9l65/s800/ldf4-1_40m_swr.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="458" data-original-width="800" height="229" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgAcP2CXez1cfF1imw5HPTBWAgGQXVIXUMGmCFbmS1Hbved2X9Lmn6_ATfod5A4niUyAwfc6yrU2xCPliLVpFvEMdZwvqZd02CZJuT09HROTpDzqtbzfIAbOhP_IDiT8HcE6zDi9BJ53ANsPPJDmvwkIIRroSzL0ihRKnCZ-okZS-o-OCETlKuATmKh9l65/w400-h229/ldf4-1_40m_swr.jpg" width="400" /></a></div><p></p><p>I am basing the antenna on my experience with a short, <a href="https://ve3vn.blogspot.com/2019/01/short-beverage-antenna-for-160-meters.html">90 meter long uni-directional Beverage</a> that I had for a short time a few years ago. It worked very well. In fact, I put the new antenna in almost the very same place, along the fence and tree line that separates two hay fields. To make it reversible, I used the same design as for the <a href="https://ve3vn.blogspot.com/2020/04/reversible-rg6-beverage-antenna.html">reversible north-south Beverage</a> made from 150 meters of RG6. The only difference is in the transformers to accommodate the change from 75 Ω to 50 Ω coax.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg3zwawco6nJwTq7A8oDx156OG_A21hM40mckspqvUcjuYE0DQtIxfALGCxYfQoU7D0AgitbY04VNaNYUkXPYhVEKeeopXfVVAjjwmt2G427WCR6vinPkXf_uwivWp-IAjcqGfrVurlaBGl6BX-cnAkqptnYrkn-JAOdUUZIYPCWRDyZSQK70VhdgVfBGtw/s800/bev_measuring_heliax.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="508" data-original-width="800" height="406" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg3zwawco6nJwTq7A8oDx156OG_A21hM40mckspqvUcjuYE0DQtIxfALGCxYfQoU7D0AgitbY04VNaNYUkXPYhVEKeeopXfVVAjjwmt2G427WCR6vinPkXf_uwivWp-IAjcqGfrVurlaBGl6BX-cnAkqptnYrkn-JAOdUUZIYPCWRDyZSQK70VhdgVfBGtw/w640-h406/bev_measuring_heliax.jpg" width="640" /></a></div><p style="text-align: left;">I picked the two best of the 40 meter lengths of LDF4-50A. The low frequency SWR sweep of both are nearly identical. The third roll (wide sweep shown further above) is decidedly worse. I measured both lengths and then dug into my piles of short Heliax scraps to make up the difference to reach about 90 meters of total length. </p><p></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjTNXVsouaW3upGuNNWM4aJLxfyRqhpgsedYz5hEmwejezoaSvguw3a1uhwC-cqBDNLegpqadvxyLtMLtb54JTYtysrkfuji3xOi0SLSIlx12q8tWF9y2seRf-oqdiYQIFkHOHLxB5DsEttGh_8rIIYJHPGU7CLAAX7xYl1EKGFylKe3K3MPgKlDG0-2MqB/s787/bev_heliax_on_fence.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="787" data-original-width="400" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjTNXVsouaW3upGuNNWM4aJLxfyRqhpgsedYz5hEmwejezoaSvguw3a1uhwC-cqBDNLegpqadvxyLtMLtb54JTYtysrkfuji3xOi0SLSIlx12q8tWF9y2seRf-oqdiYQIFkHOHLxB5DsEttGh_8rIIYJHPGU7CLAAX7xYl1EKGFylKe3K3MPgKlDG0-2MqB/w102-h200/bev_heliax_on_fence.jpg" width="102" /></a></div><p style="text-align: left;">The two lengths were placed on top of the fence line with the help of a friend and joined them with an N barrel connector. I needed his help to thread them through the trees without kinking the cable or damaging the jacket. For half the distance the bushes are thick and thorny so it wasn't much fun. </p><p></p><p>To keep the cable from drooping between supports (the log fence zigzags), rope was tied on at both ends, pulled taut and the ropes tied to conveniently placed trees.<br /></p><p>That was in early fall. There it languished until mid-December when I had the time to resume work on it. Unfortunately it could not be prepared in time for the CQ WW contests. We made do with switching the existing Beverage system (6 directions) between stations. I would like to have the new Beverage ready for the ARRL DX contests.</p><p><b>Modelling</b> <br /></p><p>Before proceeding to wind the transformers and build the switching system I turned to modelling. Although 90 meters is a good length for a short Beverage, it is unusually low and "fat". I expected these factors to affect the optimum length, and I was right.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh3BEzj98vb7rqEF0bX8N1L9rWtVIc5z8YMLYfTVjC4-ipVoOSzOXfJfQ7CH8UIvm6B3Y0St-32zHAYeOhUJUt4Hm2TJAaV7YEPVsqJ-uqNp2lIm7imYx6acRi9HN6qvuE8mcYh-umLXd7BIFoV4N3K7XhEbeObIR03gKMtipXSdt7D22l6DLjWG9ILHXWX/s737/bev_heliax_86m_up1m_azel.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="420" data-original-width="737" height="365" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh3BEzj98vb7rqEF0bX8N1L9rWtVIc5z8YMLYfTVjC4-ipVoOSzOXfJfQ7CH8UIvm6B3Y0St-32zHAYeOhUJUt4Hm2TJAaV7YEPVsqJ-uqNp2lIm7imYx6acRi9HN6qvuE8mcYh-umLXd7BIFoV4N3K7XhEbeObIR03gKMtipXSdt7D22l6DLjWG9ILHXWX/w640-h365/bev_heliax_86m_up1m_azel.png" width="640" /></a></div><p style="text-align: left;">I tweaked the length until the F/B was best. That was 86 meters. I selected one of the scrap lengths of Heliax pictured above and added it at the east end of the Beverage to make it that length. Of course the NEC2 model likely has some inaccuracy due to the ground proximity and largely unknown composition, but it doesn't hurt to at least try to get it right. </p><p></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhIIu0J2hn7WF8M8NO4xg28vy6XAfU984A1Om2uB-9A-SlrygeaT-2eEMQWh446b9sSv8m5vgbw7lhQL_4p8m_i2Ucg2dAKAEo7c2EYw2GIWTv_kBs-Q9SpxuNpbkNgMeWbbEpoFhoue6yf9LQqpGc07pYQ5PC5U6ofDkH4oU1VIjP6hEAhij6sPeHxb6b1/s211/bev_90m_up1.5m_view.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="98" data-original-width="211" height="98" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhIIu0J2hn7WF8M8NO4xg28vy6XAfU984A1Om2uB-9A-SlrygeaT-2eEMQWh446b9sSv8m5vgbw7lhQL_4p8m_i2Ucg2dAKAEo7c2EYw2GIWTv_kBs-Q9SpxuNpbkNgMeWbbEpoFhoue6yf9LQqpGc07pYQ5PC5U6ofDkH4oU1VIjP6hEAhij6sPeHxb6b1/s1600/bev_90m_up1.5m_view.png" width="211" /></a></div><p>If it turns out not to be optimum the impact is small since the RDF is unaffected by small length differences, just the F/B noticably changes. The RDF in the EZNEC model can be calculated from the difference between the gain (-15.1 dbi) and the average gain (not shown) of -24 db. Therefore the RDF is approximately 9 db. That isn't great but it is better than almost all compact receive loops like the pennant, EWE and others.</p><p>Although the 90° azimuth beam width seems poor, in my use case that's an advantage. The objective is to keep it simple for the operator for the second station in a contest. This is not my main Beverage system where better performance is needed for both contests and DXing on top band. The RDF is fine for cases where the reception is poor on the omni-directional 160 meter transmit antenna. It is less helpful on 80 metes due to the narrower beam width though, as we'll see, it is still useful. </p><p>In time I would like to supplement the east and west coverage with a short south Beverage. It would have to be a winter only antenna since it almost certainly have to be run across a hay field. There would be no point in making it reversible to the north because there's little for us to work in that direction. There is the long north-south reversible Beverage in the main receive antenna system for those brief periods when we look north towards Asia.</p><p><b>Construction</b><br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhIJapP6uD3iUL-zTPxpI-3TCbl_ni2hFyuCwRMgF6gnAdW3HgY5eEbH6Tm-6mJcPxXQPKaO0fLfG7mr1ZUvneRtqTv6sEOMqvk9o5_CJB-maqZ62SOjvduWhSCHNjOycINIiDKk-23B9DUQiFtHsUspUj1aT6kxIcwmfYX3gZ6L9Gxr82Zry23glJ5Rhwg/s365/annotated_on4un_rev_coax_bev.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="365" data-original-width="340" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhIJapP6uD3iUL-zTPxpI-3TCbl_ni2hFyuCwRMgF6gnAdW3HgY5eEbH6Tm-6mJcPxXQPKaO0fLfG7mr1ZUvneRtqTv6sEOMqvk9o5_CJB-maqZ62SOjvduWhSCHNjOycINIiDKk-23B9DUQiFtHsUspUj1aT6kxIcwmfYX3gZ6L9Gxr82Zry23glJ5Rhwg/s16000/annotated_on4un_rev_coax_bev.png" /></a></div><p>The transformers are the key to good performance. I wound the transformers before building the rest of the electronics. I used the same binocular Fair-Rite transformers as in the past, and are typically used by pretty much everyone else building Beverages. This time, rather than use Teflon liners, I used insulated wire salvaged from scrap Cat5 cable for the winding with the fewest turns. The insulation served as a protective bed for the second and longer winding made from coated magnet wire.</p><p>The annotated diagram from ON4UN's <i>Low Band DXing</i> book shows the transformer turns for this implementation. The same book estimates that the surge impedance for this Beverage should be approximately 350 Ω. The reflected signal (west direction) travels through the 50 Ω Heliax and the feed line 75 Ω, made from a combination of old RG59 and new RG6. I used the handy table in the ON4UN book for winding turns for the various transformation ratios I needed. <br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7kyHoBjj3O9PEGOrv1Rdv_H3eDddriSu9NH3N53OpkQntzLV6d9dfAuawqqYCBfBHu_WpFXp4aWYCDctIYoomjQcRo6PO5Jz1x8S15maTh-OXD4PYhgRRf_5D0TVs_p-yE0nUZ08zIz045F82T328nyvHizFUIQbnqZalQM_UMHHua5GZX2ikt874mvMS/s915/bev_heliax_xfmr_test.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="412" data-original-width="915" height="288" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7kyHoBjj3O9PEGOrv1Rdv_H3eDddriSu9NH3N53OpkQntzLV6d9dfAuawqqYCBfBHu_WpFXp4aWYCDctIYoomjQcRo6PO5Jz1x8S15maTh-OXD4PYhgRRf_5D0TVs_p-yE0nUZ08zIz045F82T328nyvHizFUIQbnqZalQM_UMHHua5GZX2ikt874mvMS/w640-h288/bev_heliax_xfmr_test.png" width="640" /></a></div><p></p><p></p><p></p><p></p><p style="text-align: left;">All of the transformers were tested on a VNA using a suitable termination resistor. I didn't bother testing the insertion loss since it was certainly better than -1 db in all cases. It is not critical for a receive antenna as long as there's enough gain that atmospheric noise can be heard in the receiver. Beverages rarely require auxiliary amplification. Use the rig's pre-amp if necessary, and a BPF if there's a strong broadcast station nearby. In my remote QTH there are no nearby broadcasters so the only strong signal is from my second station during contests. I haven't yet needed a BPF to deal with it.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjux31cncnMvOb-zlCCZXDpP5EKtBnfDvQPaqQ3Fv-rcE5riG7hsmD8I6PVteuoZJJoMqZe7KVhhNYCJdk8K7hrTtF3k11dsE8oU3RYJvbJVjvASYdcmI4XqYiWVmLc8vdKsfFvxe0KIDbvxe2EIIOlyMzyb7aiyTYSqZwHnT0QlhLIxDaYeoiQbEqSNB5t/s860/bev_heliax_enclosures.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="394" data-original-width="860" height="293" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjux31cncnMvOb-zlCCZXDpP5EKtBnfDvQPaqQ3Fv-rcE5riG7hsmD8I6PVteuoZJJoMqZe7KVhhNYCJdk8K7hrTtF3k11dsE8oU3RYJvbJVjvASYdcmI4XqYiWVmLc8vdKsfFvxe0KIDbvxe2EIIOlyMzyb7aiyTYSqZwHnT0QlhLIxDaYeoiQbEqSNB5t/w640-h293/bev_heliax_enclosures.jpg" width="640" /></a></div><p></p><div class="separator" style="clear: both; text-align: center;"></div><p></p><p></p><p>I selected enclosures for the head end electronics and for the reflection transformer. I reused a box from a retired Beverage head end for the new one. I enlarged the hole for the F connector to install an N connector and added a stud for the ground wire. For the reflection transformer I chose a very small plastic box. It is almost dwarfed by the N connector that barely fits on its surface. But it was cheap and the transformer is small.</p><p>The completed head end demonstrates that sloppy construction is
usually acceptable at low RF frequencies. I like that since I'm a disaster waiting to happen when working on circuitry. A small proto-board loosely secured
supports all but the GDT assemblies for <a href="https://ve3vn.blogspot.com/2023/09/beverage-lightning-protection.html">lightning protection</a>. There is generous wiring to the connectors to ease removal for service. There is no need for metal enclosures that will complicate construction since the coax connectors don't share the same ground.<br /></p><p>I made mistakes: one cold solder joint, one no solder joint and one transformer installed backwards. All were easy to fix. I'm prone to carelessness when working on circuitry, whether it's commercial equipment or my own projects. Bedlam usually ensues when I open up a transceiver.<br /></p><p></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiH4-z3yCZMMs-8Sr2uomX9F0Kn39NYdy1FU2GElvRN95atupsago0PI2iEJHyOJEqd_VQBN875gtLDKx39G4gmaoy0Gt4UgqfjRxWA9CSwd7PQOUvSGWV6ZrtvHFSI8mpIwYfuW99gBKofYOw105K8XDIN7_SWkxh7dUcct1Zp4PAgFOmHczkSWpSTauXE/s800/bev_heliax_headend_test.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="266" data-original-width="800" height="212" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiH4-z3yCZMMs-8Sr2uomX9F0Kn39NYdy1FU2GElvRN95atupsago0PI2iEJHyOJEqd_VQBN875gtLDKx39G4gmaoy0Gt4UgqfjRxWA9CSwd7PQOUvSGWV6ZrtvHFSI8mpIwYfuW99gBKofYOw105K8XDIN7_SWkxh7dUcct1Zp4PAgFOmHczkSWpSTauXE/w640-h212/bev_heliax_headend_test.jpg" width="640" /></a></div><p style="text-align: left;">For testing, I built a bias-T interface on a proto-board to inject 12 VDC to energize the reversing relay in the head end. It consists of a 0.1 μF capacitor and an RFC. Although, as mentioned above, sloppy wiring is acceptable at low frequencies, you can see the rising SWR at the right of the analyzer screen (7 MHz) due to the inductance of the long leads used for testing. Resistors (330 Ω and 50 Ω) represent the Beverage loads. The nominal transmission line impedance is 70 Ω or 75 Ω, so an SWR of 1.5 is what to expect on a 50 Ω analyzer.</p><p></p><p></p><p></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi0am5z1gYU7rgxE92qcQd1FXT14Id40wAn3PzyT5nmEPiV4wdlDQhdgsRD7XkYdbHC-Khje9TLOkEu3PPGijBVgawCoC8ATZwgwFTe4bSpomW_3b_OgQuZSHoWiuRzhTvsWVgugpn2DpntOKj49zALjuGsTg6_OHHwI4IYEf7ZyhIDdhR5_arhdT6Jidfn/s640/bev_heliax_headend_installed.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="321" data-original-width="640" height="321" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi0am5z1gYU7rgxE92qcQd1FXT14Id40wAn3PzyT5nmEPiV4wdlDQhdgsRD7XkYdbHC-Khje9TLOkEu3PPGijBVgawCoC8ATZwgwFTe4bSpomW_3b_OgQuZSHoWiuRzhTvsWVgugpn2DpntOKj49zALjuGsTg6_OHHwI4IYEf7ZyhIDdhR5_arhdT6Jidfn/w640-h321/bev_heliax_headend_installed.jpg" width="640" /></a></div><p style="text-align: left;">The head end was installed at the west end of the Beverage. I used RG59 for the feed line into the house since it was the right length and I had no other use for it. I tested it beforehand to ensure it was still okay, at least at low frequencies. For the rest of the run into the shack I used RG6. I used F twist-on connectors and F barrel connectors between coax segments. The RG59 was laid on the ground at a right angle to the Beverage to <a href="https://ve3vn.blogspot.com/2021/01/beverage-feed-line-interactions.html">minimize interactions</a>. I'll lift it onto an aerial messenger cable later this winter or in the spring to get it off the ground.<br /></p><p></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjv0fJD6nDZ9PyRxIZadkrTaRDyysgLON2xhH7jHlCQqMAUJUxu_cXluZhs_6KfMDnLnRa8k8Bj6xFcHKNUjF6jXO6fwY7Z-oNepE-jRWVKLclDjKIWiOBc7VSeSrruwYwmXCJCtmtsit63DB3V-RPUZHN1eA7zKTNQozGzV2clmkNOQuIZjzxRwkL2ALcH/s768/bev_heliax_termination.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="768" data-original-width="400" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjv0fJD6nDZ9PyRxIZadkrTaRDyysgLON2xhH7jHlCQqMAUJUxu_cXluZhs_6KfMDnLnRa8k8Bj6xFcHKNUjF6jXO6fwY7Z-oNepE-jRWVKLclDjKIWiOBc7VSeSrruwYwmXCJCtmtsit63DB3V-RPUZHN1eA7zKTNQozGzV2clmkNOQuIZjzxRwkL2ALcH/w167-h320/bev_heliax_termination.jpg" width="167" /></a></div><p style="text-align: left;">The tiny enclosure for the reflection transformer is dwarfed by the Heliax it plugs into at the east end of the Beverage. Both ends are grounded via 4' copper-clad ground rods for the terminations. These have proved adequate for all of my Beverages even though their ground impedance isn't great. Beverages are pretty tolerant, which is one reason I like them. In other installations it may be necessary to improve the ground rods or add short radials.</p><p></p><p>Despite all the below grade rocks and tree roots I only had to make 6 trials to drive in the two ground rods. I got lucky. In one case a few years ago it took twice as many tries to drive in one ground rod. You pull it out and try again a foot away. Trial and error is necessary.<br /></p><p>The squirrels began exploring and abusing the Beverage as soon as it was pulled along the fence line. The Heliax became a convenient rodent highway that perhaps saved them the effort of jumping from log to log. The ⅛" nylon rope at the head end was soon chewed through so I replaced it with scrap insulated copper wire. </p><p>I suspect that it was rodents rather than the usual deer that recently chewed through one of the radials on the 160 meter transmit antenna. That was easy to fix. I'm thankful that they have never (yet) chewed on the many hundreds of meters of RG6 running through the bush to the various Beverages.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjm8tddK8EWDylmrWoreLs18heHNf-rL8w-0efoV5vaZpCi57iuww_ujMWYFWJT7BGSwLqUcEMyoXeMYQDgfI6VE9P-tzvgaUrFGkKhmnpMk7O7btw2zxo1_wt83RRL2L5XhH1AQnHtZqui6GgIc3z66IUfgQaX6KWSg_SoJ1XL3TqeXT0UDX6HJBU8YBuP/s960/bev_heliax_swr_mosaic.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="270" data-original-width="960" height="180" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjm8tddK8EWDylmrWoreLs18heHNf-rL8w-0efoV5vaZpCi57iuww_ujMWYFWJT7BGSwLqUcEMyoXeMYQDgfI6VE9P-tzvgaUrFGkKhmnpMk7O7btw2zxo1_wt83RRL2L5XhH1AQnHtZqui6GgIc3z66IUfgQaX6KWSg_SoJ1XL3TqeXT0UDX6HJBU8YBuP/w640-h180/bev_heliax_swr_mosaic.png" width="640" /></a></div><p style="text-align: left;">When I first connected the antenna it didn't work. After some frantic troubleshooting I discovered that the ground wire to the head end had fallen off. Once I screwed it back on the Beverage worked as expected in the east direction. The SWR curves are hardly perfect and the scraps of feed line didn't help. I've found that Beverage antennas are very tolerant of impedance matching challenges like these.</p><p></p><p>The impedance centres near 75 Ω (SWR of 1.5), which is per the design. The cycling is most likely due to a surge impedance that differs from the design objective of 350 Ω. There are many factors to consider, though the most likely one in this case is the ground connection. The ESR (equivalent series resistance) of these ground rods in my soil is typically about 100 Ω. I could have wound the transformers for the higher net impedance of about 450 Ω, but that isn't necessary. </p><p>The impedance in the reverse direction displays more anomalies. Those are almost certainly due to the poor quality of the Heliax. It is only in the reverse direction that the Heliax is used as a transmission line to transport signals coming from the west via the reflection transformer at the east end of the antenna.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBWqJDW21V9e4luAqrHZC-dmWaKE_4KaoIOjKdI0brEbKsbUF02E1cBXDQPWiwHttnKHDb3ivRl4IX1hwAO8u4x5e0eAOxyVfCDg6kbsrAaaJKqNGWmoceztAKezJ4b1wcdLx4bKJUmpfJlo4JNx4xI9YwtxOLkVUaAGNORWAYmu7pPRiMtSG4ofu6YSnM/s640/bev_heliax_manual_controller.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="537" data-original-width="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBWqJDW21V9e4luAqrHZC-dmWaKE_4KaoIOjKdI0brEbKsbUF02E1cBXDQPWiwHttnKHDb3ivRl4IX1hwAO8u4x5e0eAOxyVfCDg6kbsrAaaJKqNGWmoceztAKezJ4b1wcdLx4bKJUmpfJlo4JNx4xI9YwtxOLkVUaAGNORWAYmu7pPRiMtSG4ofu6YSnM/s16000/bev_heliax_manual_controller.jpg" /></a></div><p style="text-align: left;">I made a switch-operated bias-T to inject 12 VDC onto the coax for the reversing function. The F connectors are for the Beverage systems and the BNC connectors are for the receive antenna ports of two radios. At the moment the new Beverage is switched manually. The switch on the left, not yet operational, will be used to manually swap Beverage systems between the two radios. The rightmost F connector is for a possible south Beverage to be used in conjunction with the new east-west short Beverage.</p><p></p><p>Assuming that the system works well, a PCB with relays will be installed for software control of system swapping and direction control of the new Beverage. It will be <a href="https://ve3vn.blogspot.com/2022/07/station-automation-design-choices.html">point and click</a> as for the main Beverage system. Implementation is straight forward but it is not a priority. I'll have more to say about this project after it is built.</p><p><b>Testing</b><br /></p><p>I compared the new Beverage to the higher performance Beverage system on 160 meters. I used two receivers for the test so that I could easily listen to both antennas concurrently. Comparing the reception of signals was interesting. <br /></p><p>Signals from Europe (northeast) were about the same on the new Beverage as on the longer east Beverage. The long east Beverage has a sharper beam width so its gain falls off to the northeast. The long northeast Beverage is, unsurprisingly, the clear winner for European signals. </p><p>Signals are stronger on the long Beverage since Beverage gain increases with length. However, that does not indicate quality of copy since both signal and noise increase. Direction and RDF are what matter. Use the receiver pre-amp if necessary to raise the antenna noise level above the receiver noise floor.</p><p> Testing the F/B and the west direction had to wait because at first the antenna didn't work in the reverse direction. Troubleshooting found that the N panel jack on the enclosure with the reflection transformer had a <a href="https://ve3vn.blogspot.com/2023/04/you-dont-need-n-connector.html">broken centre pin</a>, the ground lug was loose and the transformer was wired backwards. So many mistakes in such a small box! Well, that's not unusual for me.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEglYNyA02v_j52GC5mQLDwv3hvJ6lkL74Mf2gVRPOjmech6aehSqDkT8aebAbVpb29NRqkyGWfuUa6gm2L7zNWaBHCzwMsdNh71oc2Np54b5gx59HK7rUF4VuJIgPREooeMXPJG4edkUWs33xP3GRsqbl-4gvUoQmkFMG8gNpcgoRAWKTzAgTP7kmvu8Rjy/s466/bev_90m_vs_80m_3el_az.png" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="466" data-original-width="388" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEglYNyA02v_j52GC5mQLDwv3hvJ6lkL74Mf2gVRPOjmech6aehSqDkT8aebAbVpb29NRqkyGWfuUa6gm2L7zNWaBHCzwMsdNh71oc2Np54b5gx59HK7rUF4VuJIgPREooeMXPJG4edkUWs33xP3GRsqbl-4gvUoQmkFMG8gNpcgoRAWKTzAgTP7kmvu8Rjy/s16000/bev_90m_vs_80m_3el_az.png" /></a></div><p style="text-align: left;">When I did get it working the F/B was tested on 160 meters with stations in Europe and W7. It works very well in both directions. Performance to southerly directions was unpredictable, depending on where the signal fell into the off-the-side nodes and nulls of the Beverages being compared.</p><p></p><p></p><p style="text-align: left;">I next turned to 80 meters. It is interesting to compare the patterns of the 3-element vertical yagi and the short Beverage. There is of course a large gain difference but that is not entirely relevant. It may matter when switching from one to the other since it may also require turning the receiver pre-amp on or off. </p><p></p><p>I live with it even though I could install an external amplifier for the Beverage to better equalize signal levels. I don't because it is common for a pre-amp, even one with a BPF in front of it, to be overloaded by a nearby kilowatt transmitter. That's only a concern for SO2R and multi-op contests, which is different than for most low band operators.<br /></p><p>In my brief testing on 80 meters the short Beverage works well. The RDF of about 11 db, which is 1.5 db better than the yagi, may prove useful for digging out weak stations during contests when the main Beverage system is being used on 160 meters.</p><p><b>Done </b><br /></p><p>With this antenna completed, that's one more check mark on my long list of winter projects. It is unlikely that I'll pursue manual or software swapping of Beverage systems during this contest season. I will instead turn to other projects.</p><p>If you have the space and one or more old rolls of retired coax, consider a project like this rather than tossing them into the garbage bin. It's a simple and inexpensive way to improve low band receive performance. The improvement can be especially impressive if your main antenna is not directive, such as a vertical or inverted vee. A 90 meter (300') long antenna will fit within many urban fringe or rural properties where a full size Beverage twice that length will not.<br /></p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com1tag:blogger.com,1999:blog-6207999661586171874.post-35738799399974597862024-01-04T09:23:00.001-05:002024-01-04T09:23:48.927-05:00Article Popularity Over 11 Years<p>I'm quite surprised to still be blogging after 11 years and to do so while sustaining the same pace of articles. This is article #580, which is an average of about one article per week. Blogging is falling by the wayside in comparison to those who have taken to YouTube and similar media. Each has its place. I don't have an audience anywhere close to that of the popular YouTube ham channels. That's not my goal yet I am always surprised to learn how many are reading my blog.</p><p>Most of the traffic comes from search engines rather than regular "subscribers". That isn't surprising. Typically we search for help when we need information or when something breaks. Let's say your Hy-Gain rotator needs work. You type in "how to repair a hy-gain tailtwister" and my blog shows up high in the results. That's how most readers end up here. However, I often find that videos rank higher than blogs in the results. </p><p>I'm not chasing eyeballs so I stick with the medium that I prefer. There are no ads and I earn no income from the blog. I am not motivated by money or attention. I see the blog as one way I pay it back to the hobby that has done so much for me. It helps that I enjoy doing it. Words are how I best express myself.<br /></p><p><b>Statistical imperfections</b><br /></p><p>I have enough experience with statistical analysis and mathematics in general to be wary of simplistic interpretations of raw page views. There are many confounding factors that skew the results. The popularity of an article does not necessarily measure its quality or value.<br /></p><ul style="text-align: left;"><li>Bias to older articles: Articles published long ago have a higher probability of being searched for and read simply because they've been around longer.</li><li>Blogger statistics: I am reliant on the statistics kept by the Blogger platform. They aren't very deep or informative and since Google pretty well abandonned Blogger, there are unlikely to be improvements.</li><li>Robots skew the page hits: Like everyone on the internet, my blog is regularly plagued by robots that repeatedly hit articles, seemingly at random, that upset the statistics. A longer sampling period reduces the numerical affect of robots, since they active for only short periods and their targets shift.</li><li>Bias to my interests: You will find no articles on my blog about VHF repeaters and handheld radios. That does not mean that the subject is unpopular! The statistics are only meaningful for subjects that I write about.<br /></li><li>External site bias: Search engines are not neutral. When a search on a subject does or does not list one of my articles near the top of the list the statistics for the article are affected because people will click on the link. That does not necessarily indicate popularity. There is a similar effect when another site links to articles on my blog. Article hits are inflated by the interests of that site's owner and that site's popularity with other hams.<br /></li></ul><p>Those are the confounding factors that came to mind when I gave it a few minute's thought. I'm sure you can think of others. Keep that in mind as you read on. This article is more of an entertainment than a valid scientific analysis due to the poor data quality.<br /></p><p><b>All time top 10</b></p><p>Contesters love making the top ten. I first did so in Sweepstakes back in the late 1970s. Let's look at the all time top 10 articles for this blog.</p><ol style="text-align: left;"><li><a href="https://ve3vn.blogspot.com/2014/05/40-meters-3-element-wire-yagi.html">40 Meters 3-element Wire Yagi</a> (2014)<br /></li><li><a href="https://ve3vn.blogspot.com/2014/12/stacking-hf-yagis-basics.html">Stacking HF Yagis - The Basics</a> (2014)<br /></li><li><a href="https://ve3vn.blogspot.com/2013/12/40-meters-wire-yagi-inverted-vee.html">40 Meters Wire Yagi - Inverted Vee Elements</a> (2013)<br /></li><li><a href="https://ve3vn.blogspot.com/2016/06/adjust-yagi-by-pointing-it-up.html">Adjust a Yagi By Pointing It Up</a> (2016)<br /></li><li><a href="https://ve3vn.blogspot.com/2014/12/40-meters-4-element-wire-yagi.html">40 Meters 4-element Wire Yagi</a> (2014)<br /></li><li><a href="https://ve3vn.blogspot.com/2019/10/hy-gain-trap-repair.html">Hy-Gain Trap Repair</a> (2019)<br /></li><li><a href="https://ve3vn.blogspot.com/2016/03/3-element-coil-loaded-yagi-for-40-meters.html">3-element Coil-loaded Yagi for 40 Meters</a> (2016)<br /></li><li><a href="https://ve3vn.blogspot.com/2016/12/overhauling-hy-gain-tailtwister-rotator.html">Overhauling a Hy-gain Tailtwister Rotator</a> (2016)<br /></li><li><a href="https://ve3vn.blogspot.com/2020/01/air-core-coax-chokes-good-bad-and-ugly.html">Air Core Coax Chokes: Good, Bad and Ugly</a> (2020)<br /></li><li><a href="https://ve3vn.blogspot.com/2018/06/making-move-to-ft8-on-6-meters.html">Making the Move to FT8 on 6 Meters</a> (2018)<br /></li></ol><p>Recall what I said about statistical analysis up above before taking the list at face value. It is strongly slanted towards older articles, as we should expect. Since they've been around longer they've had more time to be searched and read, or read by following links from later articles. Nevertheless there are insights to be gained.</p><p>Notice that there are 3 articles about wire yagis for 40 meters and one for a yagi with short (loaded) elements on the same band. I've long noted their popularity. Yagis for 20 meters and up are fairly easy to buy or build, and raise. Not so for the lower bands. Most hams have no possibility of directional antennas on 80 and 160 meters, but 40 meters is often within reach, if one accepts a few compromises. </p><p>I believe that is what motivates the interest in those articles. I wrote them for pretty well the same reason! Long ago I had a wire yagi on 40 meters and I loved it. Exploring lightweight yagis on 40 meters was of great interest to me, in the hope that I could repeat my earlier success. Of course I have moved on and I now have two large rotatable yagis for 40 meters. My interest in wire yagis has waned, but not so for many others.</p><p>I'm surprised that the article about stacking basics made it to #2. I had thought the subject to be well covered by others. My exploration of the possibilities and alternatives was more of a selfish interest. Clearly others disagree and appear to welcome my addition to the knowledge base. I hope that the information is helpful.<br /></p><p>The two articles on repairing Hy-Gain products is worth a chuckle. Again, the statistics have to be considered in context. It <i>might </i>be that Hy-Gain products are prone to fail. On the other hand, more may fail or need maintenance simply because they have a large market share. A product with 10% of their sales would, all things being equal, have just 10% of the interest in similar articles. For example, I've written several articles on prop pitch motor repair that are not very popular, and that may be for no other reason beyond the fact that few hams use them as rotators. Hy-Gain is dominant in the rotator market for ham antennas.</p><p>#9 and #10 are different. Common mode chokes are poorly understood by many hams. Coax chokes are inexpensive and commonly used despite their limitations. I thought it worth a few words on their proper selection and use, and apparently others agree. There is ample high quality information out there (and referenced in the article) on common mode chokes. Is that information too esoteric for many so they come here? Perhaps, but I have no way of knowing.</p><p>The popularity of digital modes is undeniable, whether or not you are a fan. My use of FT8 and similar modes is limited. I reluctantly began to use WSJT-X on 6 meters several years ago when activity migrated to FT8. Since then I've become an enthusiastic digital operator on 6 meters. My reason is the many advantages it has for DXing on the magic band. I have given talks on the subject to various clubs as well. The interest is there and I believe that's a good thing.<br /></p><p><b>2023 (12-month) top 10</b></p><p>Change is inevitable. Whether it is the march of technology or the operating interests of the amateur radio community, the hobby is changing. You can be a <a href="https://ve3vn.blogspot.com/2020/06/dont-be-curmudgeon.html">curmudgeon</a> about it but that only serves to isolate yourself from others. That includes technology as diverse as digital modes, tubes vs solid state equipment, software vs hardware, and much more. </p><p>It was therefore of interest to me to compare the recent popularity of articles to that from the past 11 years. Again, the statistical factors at play skew the results. By restricting the measurement period to the recent past there is less skewing towards older articles. Only articles published late in 2023 are disadvantaged by the shorter sampling period. </p><p>I have only provided links for articles that do not appear in the previous list. That also helps to highlight the differences between the two sampling periods.<br /></p><ol style="text-align: left;"><li>40 Meters 3-element Wire Yagi</li><li>Hy-Gain Trap Repair</li><li>Air Core Coax Chokes: Good, Bad and Ugly</li><li>Stacking HF Yagis - The Basics</li><li><a href="https://ve3vn.blogspot.com/2020/04/reversible-rg6-beverage-antenna.html">Reversible RG6 Beverage Antenna</a> (2020)<br /></li><li><a href="https://ve3vn.blogspot.com/2014/07/notes-on-gin-pole-mechanics.html">Notes on Gin Pole Mechanics</a> (2014)</li><li><a href="https://ve3vn.blogspot.com/2020/11/160-meter-shunt-fed-tower.html">160 Meter Shunt Fed Tower</a> (2020)<br /></li><li>Overhauling a Hy-gain Tailtwister Rotator</li><li>Adjust a Yagi By Pointing It Up</li><li><a href="https://ve3vn.blogspot.com/2016/01/cw-switching-with-ptt.html">CW Switching With PTT</a> (2016)<br /></li></ol><p>There is a large overlap, especially at the top. Many older articles are of greater current interest while others are read less. While that's expected, the specifics are what interest me.</p><p>Only one of the 40 meter wire yagi articles remains in the top ten. However it remains at #1. The interest in achievable 40 meter gain antennas continues. Coil-loaded yagis and wire yagis with more elements are certainly less practical. On the other hand, the articles contain information of value to anyone considering these types of antennas. Perhaps more hams prefer construction articles than discussion about theory and models.</p><p>Hy-Gain antenna trap repair has moved up to #2. I suspect this is due to the article being relatively recent and not due to increased interest. I doubt that trap yagis have suddenly starting falling apart in 2023.</p><p>Low band antenna articles fill two of the top ten slots. Again, this may be due to their recency. I began my focus on low band receive and transmit antennas in 2017 soon after I moved to this rural QTH. It was then that the blog content shifted from small station antennas to big station antennas. I have written little about small station antennas for the past 7 years. The blog reflects my current interests.</p><p>The rankings of articles about gin poles and CW switching are unexpected. In the latter case it appears to be due in large part to a robot that was hammering that article for a while. However there has been a steady trickle of interest in both of those articles. I guess that the trickle of interest adds up over time.</p><p>I'll finish my commentary with a cautionary note about the article adjusting yagis by pointing them up. I don't do it that way any more. Big HF yagis are difficult to stand upright high enough for the tuning to be accurate. It is also quite difficult to access the feed point when the yagi is in that position. It is also easy to confound tuning due to interactions with towers, antennas and other obstacles. I now prefer to raise them <a href="https://ve3vn.blogspot.com/2019/12/tuning-big-yagis.html">horizontally to a modest height</a> that is sufficient to stabilize the feed point impedance. Of course VHF and UHF antennas have always been tuned this way since even head height can be indistinguishable from free space.<br /></p><p><b>Wrap up</b><br /></p><p>I decided to ease into 2024 with this lightweight article. Hopefully some readers will find it of interest. There are several technical articles in the pipeline that should be published in the coming weeks. But I needed a break, hence this article.</p><p>I can't promise that every article will be of interest to every reader. I speak to my interests, my observations, my experiments and my experiences. I try to do it in a way that makes the articles useful to others. Many articles strike a cord with others and become popular. Most are duds, finding little interest. That doesn't concern me. I would only be concerned if nothing I wrote was of interest. That may be the day I stop writing. <br /></p><p>Unfortunately the year has begun with several station problems that are weighing on me. Not to mention my obligations to others that are adding to time pressures. I have only turned a rig on once so far this year. The lull is temporary. Many contests and DXing opportunities are coming up.</p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com1tag:blogger.com,1999:blog-6207999661586171874.post-62212995924259763002023-12-29T11:15:00.000-05:002023-12-29T11:16:22.433-05:00Snap! Mechanical Failure at 130 Feet<p>One windy morning in early December I was out in the bush doing Beverage antenna maintenance. As I stepped back out into the hay field I happened to look up. I saw that something wasn't right. The upper yagis of the 15 and 20 meter stacks were not pointed where I had last pointed them. As I continued to watch the yagis slowly spun in the wind. The mast was turning freely. That's bad, very bad.</p><p>Despite the cold and windy weather I suited up an hour later and climbed the tower. I considered it an emergency because freely spinning yagis can do a lot of damage to the cables. Coax isn't expensive but the repairs would be lengthy and very uncomfortable due to the cold weather.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCva6RctLMg9p9M2duNxeCLjh_oUkouubpRp7RfKTkKijbYZEPy7UpMD2t1fg0TI26cE2L37nRK00WGUbK6jA9tJKOjenLZ0qi4VmjZa3zzgjKBb5hEcGflGSJJf2LPILf3ORifGL6PHMgZ1JGouTgzAvvzur8irMFtzmhBBiqGzb2jDQr_Y-T5HpYsp-L/s360/ppm_sheared_pin.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="308" data-original-width="360" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCva6RctLMg9p9M2duNxeCLjh_oUkouubpRp7RfKTkKijbYZEPy7UpMD2t1fg0TI26cE2L37nRK00WGUbK6jA9tJKOjenLZ0qi4VmjZa3zzgjKBb5hEcGflGSJJf2LPILf3ORifGL6PHMgZ1JGouTgzAvvzur8irMFtzmhBBiqGzb2jDQr_Y-T5HpYsp-L/s16000/ppm_sheared_pin.jpg" /></a></div>Without stopping to discover the cause, I installed the mast grip previously stashed at the top of the tower and secured it to a tower leg. That stopped the mast from turning. <p></p><p>I inspected the coax rotation loops and I lucky to discover that I had caught the failure before damage was done. Later, from the shack, I confirmed that the impedance of both yagis was nominal.</p><p></p><p style="text-align: left;">After dealing with the emergency, I dropped a few feet to inspect the mechanical coupling between the prop pitch motor and the mast. The trouble was easy to spot. The 5/16" × 3-½" bolt that couples the prop pitch motor drive shaft to the 2-7/8" short coupling pipe had snapped. </p><p></p><p>The original was a grade 8 bolt. After an earlier repair I carelessly substituted a grade 5 bolt. Shear forces snapped the head off the bolt. The headless bolt subsequently squirmed its way outward until the pipes were fully decoupled.<br /></p><p>Rather than repeat myself, interested readers can refer to earlier articles with the <a href="https://ve3vn.blogspot.com/2020/05/big-mast-for-big-tower-again.html">description of the system</a> and how I later improved it to prevent <a href="https://ve3vn.blogspot.com/2022/08/frankensteins-prop-pitch-motor.html">water damage</a> to the <a href="https://ve3vn.blogspot.com/2020/09/upside-down-prop-pitch-rotator.html">upside down prop pitch motor</a>. On a positive note, on this trip up the tower there was no sign of water getting into the motor or the return of <a href="https://ve3vn.blogspot.com/2022/05/diagnosing-prop-pitch-motor-trouble.html">motor trouble</a>.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEixgZEdBUKdBbB3urVDQO_ANurwXtq0F2XWpzwAfRkBUIiERy4HA1UGJAkbz3ZLc-B7ckNS5A9NCOk0cdWyJLACwgnTDDPGKabwZKS3ONpKP_HZ535nyyFVCXmf_-YMx0GWMEWDvdteL0WeCVYm0e6rbm-Ptkg7FFIaEWukabJikPxGUwY0ndYolMsBggRc/s533/ppm_mast_jack_and_grip.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="533" data-original-width="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEixgZEdBUKdBbB3urVDQO_ANurwXtq0F2XWpzwAfRkBUIiERy4HA1UGJAkbz3ZLc-B7ckNS5A9NCOk0cdWyJLACwgnTDDPGKabwZKS3ONpKP_HZ535nyyFVCXmf_-YMx0GWMEWDvdteL0WeCVYm0e6rbm-Ptkg7FFIaEWukabJikPxGUwY0ndYolMsBggRc/s16000/ppm_mast_jack_and_grip.jpg" /></a></div><p style="text-align: left;">Returning to my emergency climb up the tower, my hands were going numb from the fierce wind chill. The mast now secure, I raced to the ground before I could develop hypothermia. The speed at which I worked meant that I had to leave the yagis pointing south, which is not a terribly useful direction for me. That's where the wind wanted them and I was in no condition to fight the frigid wind. The important thing was that I averted a worse outcome.</p><p></p><p>A few days later the weather became unseasonably warm. I spent 3 hours on the tower that day to jack up the mast, disassemble the rest of the drive system and park the yagis northeast. I neglected to take a picture at the time so I took the accompanying picture after the full job was done after Christmas. Here you can see the improvised jack at rest. The weight of the mast and antennas is once again supported by the lower bearing, 5' below the mid-mast bearing plate seen here. </p><p>You can probably discern from the arrangement of the bolts how the jack functions. I used what I had available at the time, and I can't really recommend doing it this way. It was an improvisation when time was of the essence. The jack is only stable if the mast can't turn.<br /></p><p>I tossed the parts of the motor drive and mast coupler onto the workbench for when I would have time to inspect them. I had to decide whether to repair or replace the system. It couldn't be done quickly since the cold weather had returned and the holidays were approaching.<br /></p><p>I had long intended to redo the drive system because the design is awkward for maintenance and there is play in the system that allows the yagis to rock back and forth more than I'd like. Good intentions aren't good enough when I kept putting it off in favour of so many other items on my project list. This emergency moved it to the top of the list.</p><p>One thing regular readers will know is that I do not hide my mistakes. The design and its implementation are flawed. They are flaws that I believed would not cause problems or at least cause them far enough down the road that there would be ample time to plan and implement improvements. There was plenty of time, but I spent it elsewhere. It is easy to let things slip when they seem to work and so much else is waiting to be done. Let's take a closer look at the problems I uncovered.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjS0oP_0-JRsVkQsf_o9aqS3aoydSlUDrilMZ55xA7z2Iz8HX3Y8LrfnuCu1YBVHT3L4o6UuxSWk5xyQdqY-8zrtvDF_IRK5c-8DWkEilrT4WQB-gBPpa1jnJplhAixy9OklRkDD286gb0JdihdHygHN_JSIFHrpAPatHWA4Jhj7x_VjJYqdYWOo0rAzcSP/s800/ppm_coupler_and_stress.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="556" data-original-width="800" height="444" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjS0oP_0-JRsVkQsf_o9aqS3aoydSlUDrilMZ55xA7z2Iz8HX3Y8LrfnuCu1YBVHT3L4o6UuxSWk5xyQdqY-8zrtvDF_IRK5c-8DWkEilrT4WQB-gBPpa1jnJplhAixy9OklRkDD286gb0JdihdHygHN_JSIFHrpAPatHWA4Jhj7x_VjJYqdYWOo0rAzcSP/w640-h444/ppm_coupler_and_stress.jpg" width="640" /></a></div><p style="text-align: left;">I took the time to illustrate the design since it is critical to understanding it and its failings. I included a side view and a bottom view. I didn't have a blank sheet when I came up with the design since there were several constraints I had to accommodate:</p><p></p><ul style="text-align: left;"><li><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZ0L1UO6boUTHDqLy1YJaCy7rzCb9pGtU_Jf9w88npExKcsyHChbyfVac2usfZs4KMmPjvJKEFZlqFPJtYgFG4X1FqTgygPplHVveKawrA2M-V0p_BB-jVBxs9_Ij58yfIZeFgG5Tr9yQydLY4b5jaa40VtCjaeUcJHdYsrkVpSEa-Erpvks5BVvRr0dRF/s457/ppm_drive_on_plate.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="457" data-original-width="360" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZ0L1UO6boUTHDqLy1YJaCy7rzCb9pGtU_Jf9w88npExKcsyHChbyfVac2usfZs4KMmPjvJKEFZlqFPJtYgFG4X1FqTgygPplHVveKawrA2M-V0p_BB-jVBxs9_Ij58yfIZeFgG5Tr9yQydLY4b5jaa40VtCjaeUcJHdYsrkVpSEa-Erpvks5BVvRr0dRF/s320/ppm_drive_on_plate.jpg" width="252" /></a></div>The motor crown gear was welded to a 1-¼" steel pipe with an OD of 1.66".</li><li>A bearing had to take the weight of the mast and antennas since a prop pitch motor can't deal with that.</li><li>The 20' mast falls ~2' short of the bearing plate. It had to be extended to reach the bearing.</li><li>The available tower girts for bearing and motor plates resulted in a tight fit for the drive shaft between the motor and the bottom bearing.</li></ul><p>Please note that the diagrams are not complete. I left out the many washers (flat and lock), where the pipes are tapped, and several other details. <br /></p><p>I chose a 3.5" OD aluminum pipe from my stock of materials as the mast coupler. Two cross bolts (purple) connect them. There are 14 gauge (0.078") steel spacers to fill the gap between the coupler's 3.068" ID and 2.875" mast. Some play is acceptable but not too much.</p><p>The weight of the mast and antennas rests on the bottom 75 mm fully sealed industrial bearing that is designed for both axial and radial loads. A 2.875" aluminum (6061-T6) schedule 80 pipe serves as a drive coupler. It fits through the bearing bore and has one cross bolt to the mast coupler, and four 0.078" steel spacers. A short length of the drive coupler projects below the bearing plate. There is one cross bolt to connect the pipes. </p><p>There is a large 0.33" gap between the drive shaft and the drive coupler. ⅜" nuts fill the gap, but not perfectly. They are difficult to install so a gap needed to be left. Two positioning bolts help to prevent movement of the drive shaft.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiTl9X0YDuQERKZ0fKAKwXlyJ0_PXMYs-_5VPF0AF6TZvA4M21ZUuZhc6QD7V3rP5q4eFZNitEM_t8IMIhxUohaKHOjc2apojJVdfvoeiC9o8tUA3sYClPzKxFl61Tqf7taQMyPTUs7-Y_gdI9HEERxz0_9PTLcZjGDUZf5DTjrpbFUpgMdcAgDIt2RIkm4/s240/ppm_old_coupler_spacer.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="210" data-original-width="240" height="210" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiTl9X0YDuQERKZ0fKAKwXlyJ0_PXMYs-_5VPF0AF6TZvA4M21ZUuZhc6QD7V3rP5q4eFZNitEM_t8IMIhxUohaKHOjc2apojJVdfvoeiC9o8tUA3sYClPzKxFl61Tqf7taQMyPTUs7-Y_gdI9HEERxz0_9PTLcZjGDUZf5DTjrpbFUpgMdcAgDIt2RIkm4/s1600/ppm_old_coupler_spacer.jpg" width="240" /></a></div><p style="text-align: left;">It worked for several years despite its flaws. There is too much play in the drive coupler due to the lack of spacers at the bottom of the mast coupler. The adjacent picture shows one of the dual spacers fitted to the top of the drive coupler. That and the use of only one cross bolt allowed the bottom of the drive coupler to sway side to side under torque. The creaking could sometimes be heard on the ground.<br /></p><p style="text-align: left;">The bearing bore is ~2 mm wider than the 2.875" coupler. I didn't worry about it too much at the time because the crown gear on the motor can accommodate the play without binding.</p><p></p><p>However the most serious problem was the cross bolt to the drive shaft. There is a high shear stress on the bolt and pipe openings due to large gap between the pipes (red circles). The stress cycling is continuous due to the antennas rocking in the wind and when the mast is turned. That is why I selected a grade 8 bolt. In the earlier picture you can see the marks on that bolt, and on the grade 5 bolt that failed, where it passed through the pipes. There is less bending stress (orange circles) between the mast and drive coupler to the 3.5" mast coupler since the gap between them is small.<br /></p><p>I could have had a larger pipe welded to the crown gear. I didn't because the tight fit between the motor and bearing plates required fitting the drive shaft at an angle through the tower face. While that may have been a mistake there was no opportunity at the time to design a better system. At least I couldn't come up with one that satisfied all of the previously listed constraints.</p><p>Another measure I could have taken was to install more cross bolts to reduce play. I tried to keep those to a minimum because I was concerned that more holes would increase the risk of stress cracks in the pipes. That may have been a mistake since the total load isn't higher and more bolts helps to distribute the load, thus lowering point stresses. Also, when the pipes twist out of alignment under load there are greater bending stresses on the pipes and bolts. <br /></p><p>The big design questions must be left for the future. There was an immediate problem to be solved or I'd spend the first half of 2024 unable to rotate the upper 15 and 20 meter yagis. I inspected the components to determine whether they could be reused and what could be improved without full replacement.<br /></p><p>Once I decided on a course of action I reascended the tower on a unseasonably warm Christmas day to retrieve the mast coupler. I had left it there as insurance 2 weeks earlier in case the jack failed. I adjusted the jack and pulled the bearing plate so that the coupler could be slid off the mast.<br /></p><p>I was surprised that the aluminum (6061-T6) components were in good shape. The holes for the cross bolts were at most only slightly elongated by the repeated torque stress. Perhaps that was due to the thick walls and relatively large bolt diameters that distributed the stress over large surfaces. There was noticable elongation of the 5/16" holes in the steel drive shaft. There were also wear marks at the bottom of the mast coupler where movement abraded the aluminum. It was superficial so it, too, could be reused. </p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhZBZUmgWxRZQ8N4WDzkvZJkOophhIr9GnOtoaPqhEp79BrUXEjukQWsZPb9LB5JJvreE5532mKN-wl7nCMSpi7oEU6lVe1TUqD6Vi6VHTd5V1ucUQjLR3TnrH1kBhlkyJ2TYlIDTgOQzbvHSFnHaasIuAOznh0NY1aU18L3TD_3qiG6kDtmMJJYpPQbYw7/s640/ppm_making_new_coupler.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="330" data-original-width="640" height="330" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhZBZUmgWxRZQ8N4WDzkvZJkOophhIr9GnOtoaPqhEp79BrUXEjukQWsZPb9LB5JJvreE5532mKN-wl7nCMSpi7oEU6lVe1TUqD6Vi6VHTd5V1ucUQjLR3TnrH1kBhlkyJ2TYlIDTgOQzbvHSFnHaasIuAOznh0NY1aU18L3TD_3qiG6kDtmMJJYpPQbYw7/w640-h330/ppm_making_new_coupler.jpg" width="640" /></a></div><p style="text-align: left;">I gave myself one day to rebuild and reinstall the system, in the
interests of safety (I trusted the mast jack only so far) and to exploit the record breaking temperatures. It may have been a strange way to spend the holiday but you do what you have to do. I kept a couple of friends on standby in case I needed to interrupt their holiday to help with the tower work. Luckily there was no need to inconvenience them. I appreciated their willingness to come to my assistance if needed.</p><p></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmCoMUz47DfQaRLm6L5x8ddJCU10q-UN-eXP-BGPzE_bzPXxuty5zGl4s2xCqMPS1pbp1VTMR1cJqgQ-9G86ACWONXzCmWRh-c_No6gyNaHIGNMIIt1CVKJVtiWb-EY-0xNfqjwlVjiJzgoR5_3hG3z-pVsccafFt05RZswWhcQRPvEaCiUNtkJWHrRlw1/s495/ppm_coupler_positioning_bolts.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="495" data-original-width="480" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmCoMUz47DfQaRLm6L5x8ddJCU10q-UN-eXP-BGPzE_bzPXxuty5zGl4s2xCqMPS1pbp1VTMR1cJqgQ-9G86ACWONXzCmWRh-c_No6gyNaHIGNMIIt1CVKJVtiWb-EY-0xNfqjwlVjiJzgoR5_3hG3z-pVsccafFt05RZswWhcQRPvEaCiUNtkJWHrRlw1/w388-h400/ppm_coupler_positioning_bolts.jpg" width="388" /></a></div><p style="text-align: left;">All the work was done in my basement workshop since my garage workshop isn't heated and I had more lighting available for evening work. The picture doesn't show the full setup and procedure where I used levels and other tools to ensure good alignment of the new holes. I didn't work blindly with a hand drill!</p><p></p><p>I made several improvements to the drive shaft and its coupler:<br /></p><ul style="text-align: left;"><li>I widened the holes in both to accommodate a ⅜" grade 8 bolt as a coupling pin. I judged that the wider hole left more than enough material to avoid stress cracks. The widening conveniently removed the elongation of the drive shaft holes. The bolt is ½" longer than the one replaced so that the unthreaded shank is in contact with all 4 holes. For applications with shear stress you should avoid having bolt threads in contact with the pipes where the bolt diameter is thinner and therefore weaker. The threads also abrade the pipe.<br /></li><li>Two more holes were drilled and tapped so that there are 4 positioning bolts. They stabilize the drive shaft within the coupler without the need for difficult to install spacers on the cross bolt.</li><li>The positioning bolts are now grade 8. I found that their use as set screws on a constantly wiggling drive shaft rounded the tips of the grade 5 bolt threads. They were difficult to remove and afterwards I had to chase the threads in the coupler.</li></ul><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjacdSyXjbmJ8QWm7VjbT0XYyltEIymOPnEnmPpc54rBNixQSHs1pO_gBW9B3SlXqceTSGDV61bVl-UJ16it9pmpt_Zft2H9ATkJRMbkLn-n9c9H2mUORMYGoPMnwxhOTWqzm6CHEf6euO08zVKNyCZyaWwnkhHxd8j76-eHnTFOJmhYckQr6Mlc0GL_ZjN/s539/ppm_new_couplers_ready.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="539" data-original-width="400" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjacdSyXjbmJ8QWm7VjbT0XYyltEIymOPnEnmPpc54rBNixQSHs1pO_gBW9B3SlXqceTSGDV61bVl-UJ16it9pmpt_Zft2H9ATkJRMbkLn-n9c9H2mUORMYGoPMnwxhOTWqzm6CHEf6euO08zVKNyCZyaWwnkhHxd8j76-eHnTFOJmhYckQr6Mlc0GL_ZjN/s320/ppm_new_couplers_ready.jpg" width="237" /></a></div><p style="text-align: left;">I next turned my attention to the mast coupler. A second cross bolt was added. To avoid placing it too close to the bottom end, the second bolt is ⅜" rather than ½". Since there was no elongation of the original holes I saw no need to make the new cross bolt any larger. Both bolts are grade 5.<br /></p><p></p><p>New spacers were shaped for the top of the drive coupler. I added a ring spacer below the cross bolts using the same 14 gauge steel. The ring spacer is visible in the picture on the right.</p><p>There is significantly less play with this arrangement. A better solution would be to make the mast coupler from schedule 80 pipe where the ID is 2.9". That would leave a gap of 0.0125" between the couplers and eliminate the need for spacers. There was no time for that to be done.</p><p>The picture above shows the assembly from the bottom of the drive coupler. All the bolts are there, including the cross bolts through the mast coupler just visible through the pipe. A carabiner is already attached for lifting.</p><p>In addition to the enlarged holes, the water cap on the drive shaft had to be replaced. The glue on the aluminum disk seal didn't survive the trip to the ground. I cut a new one from the top of a food tin, glued and taped it to the pipe, and added caulking to prevent the tape from peeling.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgXxnjo_db9tByFg7xZJXaEbkPve2FZv61oKcFO_LV3oUv6EZhOXMDYhfhXBE1d-J9WpzSwWiod8kD8zD4bJjBcgdXaWzvO_N_-G7VzpQLbG5PxFoq_G-by_KnfaBXvgAqqpYv3jVZ-4h8AjgULPEA3_EuR8SwIyCcDrL34dONYzNTcvSn0JDxZRrpSsz70/s400/ppm_drive_coupler_connected.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="344" data-original-width="400" height="344" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgXxnjo_db9tByFg7xZJXaEbkPve2FZv61oKcFO_LV3oUv6EZhOXMDYhfhXBE1d-J9WpzSwWiod8kD8zD4bJjBcgdXaWzvO_N_-G7VzpQLbG5PxFoq_G-by_KnfaBXvgAqqpYv3jVZ-4h8AjgULPEA3_EuR8SwIyCcDrL34dONYzNTcvSn0JDxZRrpSsz70/w400-h344/ppm_drive_coupler_connected.jpg" width="400" /></a></div><p style="text-align: left;">Here you see the prop pitch motor attached with the new coupler system installed. There is almost zero play. For this design the difficult part of the installation is to wiggle the mast back and forth to align the pipes and drive the cross bolt through the 4 pipe holes. Luckily the wind was calm that day as I used a long wrench to rotate the mast back and forth until the bolt was driven home.</p><p></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjnG2x0g179XMlQzof20szfA7R5whiTUrAnz1JP5JB58QH-toMZ27cO_Zckty1QsbH7wTNkSXexuVp2OkSskt4f0mgd4jZ6q7DYPTsSLgyI-Rwg2e0TTjV9d6azWegStx3Y9igadNylAvNIgWsP8_YU5cYVl1UrlaTgfnz3RCUIcHVO9fwnxeNI29pd5kIi/s484/ppm_mast_cupler_reinstalled.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="484" data-original-width="360" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjnG2x0g179XMlQzof20szfA7R5whiTUrAnz1JP5JB58QH-toMZ27cO_Zckty1QsbH7wTNkSXexuVp2OkSskt4f0mgd4jZ6q7DYPTsSLgyI-Rwg2e0TTjV9d6azWegStx3Y9igadNylAvNIgWsP8_YU5cYVl1UrlaTgfnz3RCUIcHVO9fwnxeNI29pd5kIi/s320/ppm_mast_cupler_reinstalled.jpg" width="238" /></a></div><p style="text-align: left;">At right is the view looking down on the mast coupler and bearing. The only visible difference from the original is the added cross bolt a short distance above the bearing.</p><p></p><p>Since I didn't have an assistant, the final test had to wait until I climbed down (with a cumbersome load of steel). Back in the shack I confirmed that the rotator was working again. </p><p>I would like to do another test with a friend operating the controller while I monitor the rotating couplers on the tower. That will have to wait for a warm winter day after the holidays are over.</p><p>In the spring I'll discuss the design with a machinist and see if we can come up with a better system. As already said, it must be easy to install, remove and service. It must also not involve jacking the mast a large distance or the removal of the prop pitch motor. There are several possibilities brewing in my mind so we'll see where this goes.</p><p>I am relieved to enter 2024 with a fully functioning rotation system for the 15 and 20 meter stacked yagis. There are months of contests and DXpeditions coming up before spring arrives. I can live without being able to rotate the yagis for a while during the summer lull, and that may be my best opportunity to address the system design. </p><p>Although having a big station can be a lot of fun it is also a lot of work. Things break and maintenance is an unending job. The failure described in this article may be worse than most, but there are many smaller issues that regularly crop up. Despite few readers having towers and antennas of this size, my hope is that my description of the design, design flaws and the repair will prove to be helpful.<br /></p><p>This is my final article for 2023. I wish all of you a happy new year.</p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com0tag:blogger.com,1999:blog-6207999661586171874.post-30778331620139628202023-12-15T10:01:00.001-05:002023-12-15T10:02:04.663-05:00QRP Lessons from the ARRL 10M Contest<p>Operating QRP is not typical behaviour for someone with a station in the so-called "<a href="https://ve3vn.blogspot.com/2023/11/on-becoming-big-gun.html">big gun</a>" class. I used to do all my operating as QRP and the pleasure of it has never abandonned me. It may seem odd to put 5 watts into big antennas, and yet <a href="https://ve3vn.blogspot.com/2023/03/big-gun-qrp-in-arrl-dx-ssb.html">it is a lot of fun</a>. If you scan the results of any major contest you will notice that I am not the only one doing it.</p><p>But why QRP in the <a href="http://www.arrl.org/10-meter">ARRL 10 Meter contest</a>? My interest in the contest is limited and I needed a way to spice it up if I was to bother. Hams with small stations -- be it power or antennas -- know that the <a href="https://ve3vn.blogspot.com/2014/10/going-qrp-in-cq-ww-ssb.html">high bands make working stations easier</a> due to the low atmospheric noise. Of course the MUF has to be high enough to make it possible. A solar maximum is the ideal time to have fun on 10 meters.</p><p>To answer my own question, I operated QRP in this contest for two reasons. One was that the pace is less hectic than with high power due to the pile ups a big signal attracts. The second is that it was an interesting test of how my antennas perform. With a solar flux of about 125, 10 meters was open but marginal over many paths. That means a few decibels can have a large impact on results. So I put the antennas (and myself) to the test.</p><p>To recap, I have 4 antennas on 10 meters:</p><ul style="text-align: left;"><li>5 element yagi at 34 meters fixed to Europe (lower yagi of the <a href="https://ve3vn.blogspot.com/2021/10/lifting-10-meter-yagis.html">10 meter stack</a>)<br /></li><li>5 element yagi at 46 meters, rotatable (upper yagi of the 10 meter stack)<br /></li><li><a href="https://ve3vn.blogspot.com/2023/10/rearranging-yagis.html">Skyhawk tri-bander at 21 meters</a>, rotatable</li><li><a href="https://ve3vn.blogspot.com/2023/10/rearranging-yagis.html">TH6 tri-bander at 25 meters</a>, fixed south</li></ul><p>It is handy to have all of these directional antennas on 10; I didn't need to rotate the rotatable antennas often. Just click the mouse to select an antenna and then call the station.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiL1CdnfHf9uYYcjy095dWC0o5r-MdjsKG37ONBawEJPtkwOdvbfURAHgnjQ8uPJl_NhzF70tJAM7fovS-GbXVia7qUw2WN5HiD1vQI77zUusu94UiOYlMln3W6fOw2cXypI-mxjrwcanOrUGh8KgDNXEUyFEXNAbGfuOXv_HjLA5r4Up0DIGzuzcXREbFG/s800/7610_now_on_left.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="333" data-original-width="800" height="266" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiL1CdnfHf9uYYcjy095dWC0o5r-MdjsKG37ONBawEJPtkwOdvbfURAHgnjQ8uPJl_NhzF70tJAM7fovS-GbXVia7qUw2WN5HiD1vQI77zUusu94UiOYlMln3W6fOw2cXypI-mxjrwcanOrUGh8KgDNXEUyFEXNAbGfuOXv_HjLA5r4Up0DIGzuzcXREbFG/w640-h266/7610_now_on_left.jpg" width="640" /></a></div><p style="text-align: left;">This was my first contest using the <a href="https://ve3vn.blogspot.com/2023/10/new-rig-icom-7610.html">recently purchased Icom 7610</a> as my primary rig. After CQ WW SSB, I switched the transceivers so that the FTdx5000 is now the second radio, positioned on the operator's right. Getting used to the 7610 was a secondary objective for the 10 meter contest. It was a stretch for me to quickly learn how to use the 7610 for SO2V operation. To avoid the hassle I reverted to SO1R and used the second VFO/receiver to tune stations. I swapped the VFOs when I wanted to call a station during my occasional runs.</p><p></p><p>The 7610's power setting is measured in percent of full power (nominally 100 watts). That made me suspicious of the actual power output so I used a power meter to measure the power at various settings. The power percentage does not perfectly track the power output, although it is close. It varies by band and across the power range. For this contest I chose a setting that gave a power of slightly below 5 watts on the 10 meter band. At least this is more convenient that the <a href="https://ve3vn.blogspot.com/2019/11/qrp-for-ftdx5000.html">3 db attenuator</a> I built to use the FTdx5000 on QRP due its 10 watt minimum power setting.</p><p>Conditions at the start of the contest on Friday evening were poor. It was well past sunset and few signals were to be found. Those that I did hear were weak and not really worth calling with QRP. I put off operating until Saturday morning. I got up early to catch the sunrise opening. Although many Europeans were heard before sunrise their signals were weak. I had to wait until signals became stronger. I began filling the log soon after 1230Z. </p><p>Europe was coming in strong and it was easy to work stations with 5 watts and the 5-over-5 stack. Indeed, Europe was the source of about half my contest contacts and the bulk of the multipliers (65 countries overall). That is despite the brief openings. I was able to get as far as UA, UR, 4X and 5Z. By late morning the Europeans faded to only a trickle of stations in F, EA and CT. The path closed soon after their local sunset.</p><p>The rest of the day was spent hunting stations to the south, and later to the west. I could run Europeans with QRP but runs were painfully brief to the US and I frequently lost my run frequency to North American stations that couldn't hear me. However, <a href="https://ve3vn.blogspot.com/2017/03/i-hate-running.html">running is mandatory</a>, even with QRP. If you don't it is impossible to work the large number of casual contesters who only S & P. I kept my run attempts brief but frequent. </p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiG6PprTonBHo6hXmXbFauNlgcYixnJqM1ZDXFbCEMg-sxSM64YOfMVsgtNWn9UE9rLpzw0GXJtg9CpYfooWfGnJ_O4oT7hZaRe8ANVV2GNkoTZLc7ttVjvI0uDufzpkT4SfepMSiEGfj06Sy4YROMSku32nc05zP5g7sFCtEv49z__2JWFxIXqIEmv7C9E/s536/skip_zone_arrl10m.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="450" data-original-width="536" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiG6PprTonBHo6hXmXbFauNlgcYixnJqM1ZDXFbCEMg-sxSM64YOfMVsgtNWn9UE9rLpzw0GXJtg9CpYfooWfGnJ_O4oT7hZaRe8ANVV2GNkoTZLc7ttVjvI0uDufzpkT4SfepMSiEGfj06Sy4YROMSku32nc05zP5g7sFCtEv49z__2JWFxIXqIEmv7C9E/s16000/skip_zone_arrl10m.jpg" /></a></div><p style="text-align: left;">Propagation under the marginal conditions was intriguing. The most important aspect was the large size of the skip zone. It was both a curse and a blessing, as I'll describe. The map above is my attempt to illustrate my observations, and my successes and failures.</p><p></p><p>Stations at the edge of the skip zone would be S0 one minute and S9 the next. It was very evident with MN and MB to the west and W5 and W0 to the southwest. It was a lot like sporadic E openings on 6 meters, except that sporadic
E, also a staple on 10 meters, did not appear to be evidence despite the
nearness of the winter season peak.</p><p>As a QRP operator I had to check station signal levels often to catch those peaks to increment my small total of state and province multipliers. This is where entering the assisted class came in handy. I could rapidly check on stations with a click of the mouse. I used both human and skimmer spots.<br /></p><p>Particularly galling was that I was shut out of most of W4, other than Florida. That is the reason my state and province total of 49 multipliers was so low. I missed GA, TN, AL and KY. I heard many of them but weakly on back scatter. Unlike W1/2/3/8/9 stations that I could work on back scatter (mostly just the big guns), the added distance to W4 made it too difficult for QRP. W5, W6 and W7 were easy to work most of the time. The same with the western provinces from VE4 to VE7. A few Maritime provinces were workable on back scatter but, again, I missed most of those multipliers.</p><p>That's the con. Now for the pro case. Everyone has a skip zone centred on their QTH. For the bulk of the US eastern seaboard and south, they were at a relative disadvantage working the Caribbean and, occasionally, Central America and the north coast of South America. There aren't many stations there but almost every one is a multiplier. There were many times when I could sail over their skip zone and work those stations, right through modest pile ups. That was only in the morning because in the afternoon I could not compete with those further to the west that were in a similar relative position to me. Skip went long early as the MUF fell.<br /></p><p>Back scatter was a puzzle that I had to solve since signals are very weak in comparison to the direct propagation path. QRP is not conducive to effective communication via back scatter. Yet it is the only option to reach stations within the skip zone. Every attempt was a roll of the dice and I had to find a way to increase the probability of success. Sometimes it was simply of matter of trying every few minutes to hopefully catch a small upward variation of the scattered signal strength. </p><p>Calling a big gun has the best chance of success on back scatter since they have the antenna gain to better hear my signal. Unless you recognize the call signs of those stations you can only go by what the S-meter tells you. Obviously, the stronger you hear them, the better.</p><p>Equally important is listening to who they're working. That tells you where their yagis are pointed. Your best chance of success on back scatter is to point in the same direction that they are. Sometimes that is northeast to Europe and other times it's south to the Caribbean or west to the Pacific. That's true no matter where the target station is located. Early in the day when the band was open to Europe, northeast was best. That suited me well since my 10 meter stack is most effective in that direction. </p><p>With four antennas at my disposal and the ability to point in various directions, it was a simple matter of clicking through the options and seeing which antenna netted the strongest signal. Then I call and hopefully work them. When you have only one antenna, testing the back scatter path by constantly rotating the antenna is time consuming. The wealth of antennas was highly advantageous.</p><p>I decided early on Saturday to change my operating plan to better utilize the propagation that was available. I had intended to operate mixed mode (SSB and CW). Since signals levels were generally poor I decided to stick with CW. I certainly would have had a higher score operating both modes, although I suspect that I would have been less competitive. Due to the lack of daylight at this latitude, the openings were shorter. Stations further south had the advantage since they experienced a higher MUF. Their advantage is greater with SSB due to the lower SNR.</p><p>Late in the afternoon the band opens to the Pacific and east Asia. The pile ups on the few VK stations were intense. I had to wait for their rates to drop before I had a chance. With no other callers it was no problem to work them. The same can't be said for Japan and stations further west on mainland Asia. The low solar flux had the band closing soon after sunset, which is nearly coincident with our sunrise. Signals were weak and not workable with QRP, even with 5 elements 46 meters up. Very soon they were gone. I heard long path Asian stations in the morning that were also unworkable with QRP.<br /></p><p>Was I competitive? Did I win? Reports on <a href="https://www.3830scores.com/">3830</a> suggest that I may come out on top in CW QRP (unlimited/assisted). Not everyone posts on 3830 and scores will change after log checking. I didn't set out to win, just to have fun and test the station. It would be nice to win even though that was not my objective. Time will tell.</p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com1tag:blogger.com,1999:blog-6207999661586171874.post-38102745537815238632023-12-07T22:50:00.001-05:002023-12-10T11:49:36.836-05:00Stubs for Attenuating Harmonics - an Experiment<div><p>I'll start with a funny story. There were 3 of us doing a M/2 (multi-op, two transmitter) operation in CQ WW CW at the end of November. We kept both seats occupied for almost the entire 48 hours. As you might guess it was a tiring effort when each of us had to put in 32 hours on average. We got into this situation when our fourth operator had to cancel at the last minute.</p><p>Sleep deprivation is an occupational hazard for dedicated contesters. We may be able to do it, but not always with good results. It explains what happened to me on Sunday morning when the band opened to Europe on 20 meters and the running began. The run was going quite well when I was perturbed to find that an imposter using my call had come on frequency and began to run stations. The interference was high and I was incensed that some joker was going to mess up a lot of logs.</p><p> After a string of expletives that surprised my operating partners, I QSY'd a few kilohertz and resumed running. I made a mental note about the letter I ought to write to the contest committee describing the incident. </p><p>Two days later, one of us (VE3KI) did a log analysis. He remembered the incident and pulled up the time interval in the log. I think I turned a little red when he shared what he found. </p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjC-iupHjUEXbz7E6p9sVZYPMYVITg3UP5WlRaFNlW0V2SpYW6XPCM-_ccwAjUea3DxtyR3GDxjWuqGx2_7GeC-bZ-t35_FPHvj-VVmCqege1-wUajVAaFqkWvcJljBByiyX5z5Tjz4VGfmMo2Lbv5Tov2v7vi8nNdTfEGaYBEmW-GIXIZ3karqPdBYYJ5x/s656/cqwwcw2023_harmonic_interference.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="126" data-original-width="656" height="123" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjC-iupHjUEXbz7E6p9sVZYPMYVITg3UP5WlRaFNlW0V2SpYW6XPCM-_ccwAjUea3DxtyR3GDxjWuqGx2_7GeC-bZ-t35_FPHvj-VVmCqege1-wUajVAaFqkWvcJljBByiyX5z5Tjz4VGfmMo2Lbv5Tov2v7vi8nNdTfEGaYBEmW-GIXIZ3karqPdBYYJ5x/w640-h123/cqwwcw2023_harmonic_interference.png" width="640" /></a></div><p style="text-align: left;">The data was right in front of me on the screen, but I didn't look. That's what sleep deprivation will do to you! </p><p></p><p>The incident had me thinking about harmonics and how much more I can do to reduce their intensity. I am using low power BPF on both stations, and nothing else to prevent inter-station interference. The BPF are good but they cannot suppress the harmonics generated by the amplifiers. That requires high power filters after the amplifier.</p><p>Low power BPF are not the ultimate solution for SO2R and multi-op contesting. I selected them well aware of the limitations. I understood that I might eventually require high power BPF or stubs, or both. I can avoid the harmonics very easily when operating SO2R, but it is not so easy to coordinate with others in a multi-op. That takes communication and vigilance, or perhaps software to flag the risk.<br /></p><p>High power BPF are expensive and the insertion loss typically ranges from -0.2 to -0.6 db. For low power BPF you can compensate for insertion loss by increasing the amplifier drive by 5 to 10 watts. Not so with high power BPF. The dissipated power can be quite high and may require fans to vent the heat. Can stubs do an effective job of attenuating amplifier harmonics, and let the low power BPF take care of transmitter spurious emissions? I have tube amplifiers which generally suppress harmonics well, due to the tuned pi output network. When I switch to solid state amps, as planned, the amplifier-generated harmonics will almost certainly increase.</p><p>I decided that it was time to do an experiment. I wanted to see for myself <a href="http://www.vibroplex.com/techdocs/INRAD/MII_W2VJN.pdf">how well a stub can suppress harmonics</a> and (hopefully) not otherwise interfere with station performance. I have the necessary equipment so an experiment was easy to arrange.</p><p>Before delving into the experiment, it is worth taking a moment to consider what it is that we want to accomplish. The following are the concerns I identified at the start of my quest:</p><ul style="text-align: left;"><li>Which harmonics are potentially deleterious, and which are benign</li><li>Which harmonics can be effectively attenuated</li><li>Bandwidth and depth of the harmonic notches</li><li>Impact of the stub on the fundamental band of operation (insertion loss and SWR)<br /></li><li>Effect of the load (antenna) impedance on stub performance</li></ul><p>It should not be a surprise that questions about stubs overlap with those of filters in general because a stub is a filter. Fixed components (capacitors and inductors) have been replaced by a network with strongly correlated L and C components due to the structure of transmission lines. You trade flexibility of filter design in return for simplicity. We will see that, as always, there is no free lunch. </p><p>For the purpose of the experiment I went into the basement and looked over my inventory of new and used coax. I chose an ancient length of Amphenol brand RG8, about 16' (5 meters) long that had N connectors on both ends. I have no recollection of where it came from, how old it is or what use I made of it in the distant past. It was therefore important to assess its quality before proceeding. I connected it between the ports of my recently calibrated VNWA3 and swept it from 160 to 6 meters.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjcE58TFAlx1rAPlYtbyx20ESb6Iki8PRvei5a-V1eL9KKErHzo_5kGPs2Ir_yOaCkDm5n1jtNeNcfVtSicsiZSMxHECw8wdLajQ7101Ysdlzp3E6ZhlAkLBcU7P0Vzln_TveyJIEcUVf-_p7A6SS3ZcdwidBqMrSfnBuGh0gTOdAIyHLQSRy_0SMUTESP5/s624/rg8_15.3ft_through.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="456" data-original-width="624" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjcE58TFAlx1rAPlYtbyx20ESb6Iki8PRvei5a-V1eL9KKErHzo_5kGPs2Ir_yOaCkDm5n1jtNeNcfVtSicsiZSMxHECw8wdLajQ7101Ysdlzp3E6ZhlAkLBcU7P0Vzln_TveyJIEcUVf-_p7A6SS3ZcdwidBqMrSfnBuGh0gTOdAIyHLQSRy_0SMUTESP5/s16000/rg8_15.3ft_through.png" /></a></div><p style="text-align: left;">It measured better than I expected. The impedance is good and the insertion loss is only a little worse than the specification for new RG8. For example, at the (randomly set) 33.5 MHz marker the loss is -0.24 db. That's only -0.055 db worse than the -0.185 db spec. However, its random length doesn't correspond to any amateur band. I only knew that, from its length, it would be effective within the HF spectrum. I declared the cable adequate for the experiment.</p><p></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj1DyqFKG8cwrTw4AqAV_-16EoUohiWVV3Y8S21Wvxx7K7L8JRzeMC_3UggGz5v8jNwfNCo7QcJ3UL36gwehBMQz64aEGy5wL1o6176aYt3nvj-GXYMoPSWdaAezB51twJf11rT7-mMiblhuIN5u3Wzu0AbS4dqOzC3JHfmt28YuMgn1ze73R5u6aJnf7QW/s446/stub_test_setup_mosaic.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="418" data-original-width="446" height="375" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj1DyqFKG8cwrTw4AqAV_-16EoUohiWVV3Y8S21Wvxx7K7L8JRzeMC_3UggGz5v8jNwfNCo7QcJ3UL36gwehBMQz64aEGy5wL1o6176aYt3nvj-GXYMoPSWdaAezB51twJf11rT7-mMiblhuIN5u3Wzu0AbS4dqOzC3JHfmt28YuMgn1ze73R5u6aJnf7QW/w400-h375/stub_test_setup_mosaic.jpg" width="400" /></a></div><p style="text-align: left;">I inserted a BNC T between the VNA port leads and, with the help of adaptors, connected the coax to the T. The other end, with more adaptors, is terminated with a BNC short from a VNA calibration kit.</p><p></p><p>The length of the coax is 16'-8½", which is 16.7' or 5.1 m. The length is measured from the through-line centre of the T to the short cap at the far end. </p><p>Assuming the nominal VF (velocity factor) of 0.66 for RG8, without compensation for the VF of the adaptors, the cable's electrical length is 1λ at 38.8 MHz.</p><p>The test setup was then swept from below the predicted fundamental frequency of 9.7 MHz (where the stub is ¼λ long) to beyond the fourth harmonic. The first predicted notch is at 19.4 MHz (second harmonic) where the stub length is ½λ; the second predicted notch at 38.8 MHz is where the stub length is 1λ. Markers were placed inside the notches and bracketing the fundamental frequency. [Note: the frequencies are not exact multiples due to the limited number of discrete points sampled by the VNA.]<br /></p><p>Were this a proper stub the fundamental and the harmonic notch would be within amateur bands. However, this test is sufficient to the requirements of the experiment. It is straight forward to scale the measurements to nearby amateur bands.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJk2-RTjsW7uvm5F-9HEpcIESQDGJzB4UxFTX4N_kpKdHVLuk5p7IYWsr7892wsbx2gFgzIOKYGuTu18IWqeXx3LWhhizqTyZaf9EE0MO5k4_2k6O5V8yV5Yv2OE0fRwsBK5vw_HoJvGvZIRTJ3zVMGs8o76xqdi80hA_tP9NWZAU6_bfLjVSok3N9oNO6/s624/rg8_9.7mhz_shorted_notches.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="456" data-original-width="624" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJk2-RTjsW7uvm5F-9HEpcIESQDGJzB4UxFTX4N_kpKdHVLuk5p7IYWsr7892wsbx2gFgzIOKYGuTu18IWqeXx3LWhhizqTyZaf9EE0MO5k4_2k6O5V8yV5Yv2OE0fRwsBK5vw_HoJvGvZIRTJ3zVMGs8o76xqdi80hA_tP9NWZAU6_bfLjVSok3N9oNO6/s16000/rg8_9.7mhz_shorted_notches.png" /></a></div><p style="text-align: left;">As you can see, the predictions were accurate. In practice you should cut your stubs long and trim them until they resonate where you want, just like you would to adjust a wire dipole. Coax has manufacturing variations that can render an accurately cut stub too short for its design frequency. The only recourse is to toss it aside and try again.</p><p></p><p>I plotted a variety of S11 curves to illustrate how the notch behaves and works as a filter. Around the stub resonance the real component of the impedance approaches 0 Ω; that is, a dead short. This is an important factor for understanding how the stub work, that will be discussed further below.</p><p>The stub is not transparent away from its resonant notches. The presence of the stub adds reactance into the transmission line that can be highly disruptive across the spectrum of interest. It is only at the fundamental frequency that the reactances cancel and the stub effectively disappears. Markers 1 and 2 are placed at the SWR 1.1 points surrounding the fundamental frequency of 9.7 MHz since I consider those to be the boundaries of the stub's usable pass band. <br /></p><p>Notice the depth of the notches: -27.7 db at 19.4 MHz (second harmonic) and -24.3 at 38.9 MHz (fourth harmonic). The notches can be deeper with better coax because loss reduces notch depth. That is also why the upper notch is a few decibels less. </p><p>The reason coax loss matters is because for total cancellation of the incident and reflected wave the amplitudes must be equal and of opposite polarity. It is not enough for the phase difference to be 180°. To achieve a -20 db notch the amplitudes must match to within 1%. For a -30 db notch the amplitude match must be 0.1%. </p><p>To illustrate the impact I tested a short length of LMR400 as a shorted stub. It was similarly equipped with N connectors and adaptors, and attached to the T connector between the VNA ports.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhuFEJklPuZjYEbA5KeRGDmT3VMj7nmXq2YD5TvhlTj8Po7Y16IhculzUK-BO4ofY2puh5E2TXvcDzQ-f_Qj-EdBAJJoxjEXXcDGkL0Jqa_UeqJwSKJJl-lLHfEI8cI9u2GOoofMRcz1IaUFGZTD20aMhgKCVUWy4hyP8BFMNstwubLAfcLNd7Vz6wOsIku/s624/lmr400_notch_74.1mhz.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="456" data-original-width="624" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhuFEJklPuZjYEbA5KeRGDmT3VMj7nmXq2YD5TvhlTj8Po7Y16IhculzUK-BO4ofY2puh5E2TXvcDzQ-f_Qj-EdBAJJoxjEXXcDGkL0Jqa_UeqJwSKJJl-lLHfEI8cI9u2GOoofMRcz1IaUFGZTD20aMhgKCVUWy4hyP8BFMNstwubLAfcLNd7Vz6wOsIku/s16000/lmr400_notch_74.1mhz.png" /></a></div><p style="text-align: left;">We've improved the notch a few decibels. Because the stub is short the harmonic notch is at 74.1 MHz. Since loss is (roughly) proportional to frequency and length, the results are applicable to HF stubs. </p><p></p><p>It is possible to achieve deeper notches with hard line like Heliax. However, notch depth is not the only important parameter. </p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjIzD6jO0XdPVMmeakSs6dCbpACg-ROAtvNNv9DU9vs6jw6jqEEpHfNwE1Nn2mYEaH7cIDbAXrJsPJ9v4AjQXlqkvDiG_CFKq1m1rP5PFtqBQti5gQ9rAvQW7y94Ay34Yanbg0nl_44mBwgo7Obtm3KLLq5ddcAOQHSFpDUVZMMx2wbELvUo4q85RblvfI_/s624/rg8_9.7mhz_shorted_passband_stopband.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="456" data-original-width="624" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjIzD6jO0XdPVMmeakSs6dCbpACg-ROAtvNNv9DU9vs6jw6jqEEpHfNwE1Nn2mYEaH7cIDbAXrJsPJ9v4AjQXlqkvDiG_CFKq1m1rP5PFtqBQti5gQ9rAvQW7y94Ay34Yanbg0nl_44mBwgo7Obtm3KLLq5ddcAOQHSFpDUVZMMx2wbELvUo4q85RblvfI_/s16000/rg8_9.7mhz_shorted_passband_stopband.png" /></a></div><p style="text-align: left;">The above plot is restricted to HF and the markers have been placed for a discussion about bandwidth. I want to know the widths of the pass band and stop band. Their definitions are not rigid so I chose my own bandwidth definitions: SWR better than 1.1 for the pass band into a 50 Ω load (matched antenna); and second harmonic suppression better than -20 db. You are free to choose your own definitions if you don't like mine.</p><p></p><p>The pass band width is 13% for both the 19.4 MHz RG8 stub and the 74.1 MHz LMR400 stub. That appears to be consistent with all or most 50 Ω coax. That is far wider than the HF band segments that are relevant to contesting; the worst case is 8.6% between 3.5 and 3.8 MHz. It is fair to conclude that a coaxial stub filter designed to suppress harmonics from operation on any HF band contest segment will not affect performance on that band. That's good news.<br /></p><p>The bandwidth of the notches is not as good according to my criteria. The -20 db second harmonic stop band between 19.11 and 19.69 MHz is 3%. It is narrower yet for the fourth harmonic. For lower loss coax the stop band is wider, but not by much; it's also near 3% for the 74.1 MHz notch of the LMR400 stub. The stop band is wide enough to cover most but not all of the contesting segments of the HF bands from 7 MHz and up.</p><ul style="text-align: left;"><li>3.5 to 3.6 MHz: 2.9%; 3.6 to 3.8 MHz: 5.6%; 3.5 to 3.8 MHz: 8%<br /></li><li>7.0 to 7.2 MHz: 2.9%; and 7.0 to 7.3 MHz: 4.3%<br /></li><li>14.0 to 14.35 MHz: 2.5%<br /></li><li>21.0 to 21.45: 2.1%<br /></li><li>28.0 to 29.0: 3.6%</li></ul><p>The low band figures are not as daunting as they appear. First, 160 meters is not discussed since we are only interested in the pass band and not the stop band because it's the lowest of the 6 contest bands. Second, harmonic filters for 15 and 10 meter are not needed since there are no higher HF contest bands to interfere with. Third, phone contests are less plagued by harmonics because, due to the higher frequencies of those segments, it is usually adequate to tune the stubs for the CW and RTTY segments. For example, the harmonics of 3.7 MHz are 7.4 MHz, 14.8 MHz, 21.2 MHz, etc. That sixth harmonic on 15 meters is usually so weak that it requires no additional suppression. Harmonics from operation on 160 meters is similarly of limited concern for most contesters.</p><p>The third harmonic of 7 MHz can be notched with an open stub. However, the insertion loss and SWR on the fundamental are less than ideal because the optimum pass band for an open stub does not coincide with ⅓ the frequency of the available notches. For the length of RG8 measured above, when it is employed as an open stub, for the best correspondence of a notch and operating frequency, the insertion loss is -0.34 db and the SWR is 1.75. Those are not acceptable. [Note: VNA plots not included.] <br /></p><p>That aside, it is arguably sufficient to have harmonic stubs for 80, 40 and 20 meters since the harmonics for 160, 15 and 10 meters are not a significant interference risk. The 80 meter stub deal with harmonics on 40 and 20 meters; the 40 meter stub for 20 and 10 meters; and the 20 meter stub for 10 meters. Since a shorted stub can only suppress even harmonics, we can't use one for the 40 meter third harmonic on 15 meters.</p><p>At this point it is worthwhile to step back and ask a rhetorical question: is a coax stub sufficient to attenuate harmonics to an acceptable level? I hope that you'll agree that the answer is no. Lowering the harmonic by -30 db is good but not great. It depends on the unattenuated strength of the harmonic. Since we're discussing this in the context of amplifiers, we'll set 1 kW as the baseline.</p><p>If the second harmonic specification of the amplifier is -50 dbC (-50 db relative to the fundamental carrier) the harmonic power is 10 mW. That's a lot, although context matters. A coax stub will further knock it down to -80 dbC. A well-designed BPF will do even better. Two coax stubs in series can perform as well as a BPF. It is equivalent to increasing the order of a traditional filter. </p><p>A BPF attenuates all out of band energy and not just the even harmonics. Its pass band insertion is typically -0.2 to -0.6 db depending on the filter design and the frequency. High power BPF often need fans to exhaust the dissipated power.</p><p>Stubs are more commonly used in conjunction with low power BPF since the BPF can't suppress harmonics generated by the amplifier. Certainly they attenuate harmonics generated by the transmitter, so that the amplifier doesn't amplify them, but the amplifier has its own non-linearity that generates harmonics regardless of what appears at the input. Amplifiers with tuned inputs attenuate transmitter harmonics regardless of whether a <a href="https://ve3vn.blogspot.com/2020/07/choosing-band-pass-filters.html">BPF is placed between the transmitter and amplifier</a>.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEit1wTiEBP7nK0_G7Fip7Ui91x4C1O2P7J-iPrtF_qAa0y1-Z2OcZRV1WYzH5cRhyphenhyphenuRKxCcTqxRWjd-7u8SUeo5keTK0PQ5mtAS-rDqBM_zDTxWDmFzcYhfE3zOdF9j9q2hBmw6WsdWXlhHy_Dus9I-XDGWwJYV6l-NmXjHJr9F-B0fN-bcuJ3RGwtwu5Kv/s467/harmonic_radiation_3modes.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="467" data-original-width="443" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEit1wTiEBP7nK0_G7Fip7Ui91x4C1O2P7J-iPrtF_qAa0y1-Z2OcZRV1WYzH5cRhyphenhyphenuRKxCcTqxRWjd-7u8SUeo5keTK0PQ5mtAS-rDqBM_zDTxWDmFzcYhfE3zOdF9j9q2hBmw6WsdWXlhHy_Dus9I-XDGWwJYV6l-NmXjHJr9F-B0fN-bcuJ3RGwtwu5Kv/s16000/harmonic_radiation_3modes.jpg" /></a></div><p style="text-align: left;">There is another place where harmonics can be attenuated: the antenna. Dipoles and yagis made of dipole elements present a high impedance to even numbered harmonics, assuming the elements are not loaded. If the elements are loaded, the third harmonic may also be attenuated. I used that to good effect when designing my 3-element 40 meter yagi to eliminate the <a href="https://ve3vn.blogspot.com/2020/03/40-meter-dilemma-interactions-size.html">resonance within the 15 meter band</a>. Of course a multi-band yagi may not attenuate harmonics at all. For example, the second harmonic of 20 meters and a tri-band yagi.</p><p></p><p>The presence of a mismatch at the antenna may not be enough. Any harmonic energy that reaches the feed point has to go somewhere. If the antenna presents a poor match (high SWR) our best hope is that it is reflected. If the coax outer surface presents a more favourable impedance, the harmonic energy will "leak" around the feed point and become common mode current on the coax shield. It can then radiate and/or return to ground by some circuitous route. CMC (common mode chokes) help prevent harmonic leakage if designed to be effective at the frequencies of the harmonics. Often CMC are optimized for the fundamental frequency.</p><p>Assuming we have well-designed high power BPF and coax stubs, should we care what happens to harmonics at the antenna? Perhaps not, although there is a valid concern when the antenna is not a close match to 50 Ω. All filters, and that includes BPF and stubs, only work as designed for specific port impedances. When there is a mismatch at the antenna or a fault due to poor coax or switching equipment, the filter may not perform as intended.</p><p>For this reason I did a further set of tests. I created a mismatch on the load side of the stub and measured the effects with the VNA. These were simple tests to probe the parameter space rather than a comprehensive analysis. I am not an expert and there was a risk that I would not design the experiment to get a broadly applicable result.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggJ15YbROXGqTf_2Gkaf15QbHoXGIOMkV7ler2LCFh1EcwdZ-fcCBJi-uCwOam6IermjVxMTwdN9bpSK1wf6VTFLU6hkXVwNixCeTDIP_DY_tn15-N9wa9nRAc5oYP1zj2TVqK9W-em01VYmdjGlofqJO12ZbPJTxPG5QDEsf5q9VCEj5I_zBO8hoWfLgT/s959/stub_swr_tests.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="527" data-original-width="959" height="352" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggJ15YbROXGqTf_2Gkaf15QbHoXGIOMkV7ler2LCFh1EcwdZ-fcCBJi-uCwOam6IermjVxMTwdN9bpSK1wf6VTFLU6hkXVwNixCeTDIP_DY_tn15-N9wa9nRAc5oYP1zj2TVqK9W-em01VYmdjGlofqJO12ZbPJTxPG5QDEsf5q9VCEj5I_zBO8hoWfLgT/w640-h352/stub_swr_tests.jpg" width="640" /></a></div><p style="text-align: left;">On the left I placed a 50 Ω resistor in parallel with the transmission line between the stub and the load (right VNA port). On the right I substituted a 100 pf parallel capacitor. In both cases I am using the original RG8 stub that has its fundamental frequency at 9.7 MHz. I skipped trying this with series elements since they would have taken more time to set up. Let's look at these two cases in turn.</p><p></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjuocQforC24zj0b4zHHVsLWMQDG_CR5j92LsVC6wDJfSDWJjerEeoV6RTENkyj2W1hFxRI4_ruW0q8dKGeVt_VfKVoy2rhoH1jZwLOwF42KR2w9h1I4YjQMLIvpEFrrMCk5LbmBWHSqQIsoe0q0MeDp-EvlKKrYxaOIRDUIA7HRv6BvhJHETg4bYqBcbyr/s624/rg8_9.7mhz_shorted_notches_swr2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="456" data-original-width="624" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjuocQforC24zj0b4zHHVsLWMQDG_CR5j92LsVC6wDJfSDWJjerEeoV6RTENkyj2W1hFxRI4_ruW0q8dKGeVt_VfKVoy2rhoH1jZwLOwF42KR2w9h1I4YjQMLIvpEFrrMCk5LbmBWHSqQIsoe0q0MeDp-EvlKKrYxaOIRDUIA7HRv6BvhJHETg4bYqBcbyr/s16000/rg8_9.7mhz_shorted_notches_swr2.png" /></a></div><p style="text-align: left;">With the parallel resistor the notches didn't change. Not surprisingly the SWR at the 9.7 MHz rose to 2 and there is an insertion loss due to the use of a real resistor rather than radiating one as found in an antenna. This is a good result. Unfortunately it is unrealistic since it is rare for a mismatch to be purely resistive. Thus we come to the second case.</p><p></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjjRZaRYKcfLFqlzWa6RdcmnoC8CJGm0APEbfn_mq3f2FaxN6TqnBZuLIabG0-7bqqngjlv0GwyBP5gMutFdl9ZkjKxlrOkkx7os5fNL1p4WWOIOExU46uhn-t38ARY9NkUNDmocvNkiPp9p7OhQkeREvKStYbsL338FaNbrtev-yuq5opoJprhzUdiKpTF/s624/rg8_9.7mhz_shorted_notches_parallel-100pf.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="456" data-original-width="624" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjjRZaRYKcfLFqlzWa6RdcmnoC8CJGm0APEbfn_mq3f2FaxN6TqnBZuLIabG0-7bqqngjlv0GwyBP5gMutFdl9ZkjKxlrOkkx7os5fNL1p4WWOIOExU46uhn-t38ARY9NkUNDmocvNkiPp9p7OhQkeREvKStYbsL338FaNbrtev-yuq5opoJprhzUdiKpTF/s16000/rg8_9.7mhz_shorted_notches_parallel-100pf.png" /></a></div><p style="text-align: left;">The notch position and performance are unchanged. What has changed is the behaviour within the pass band. The SWR at 9.7 MHz has increased to approximately 1.4. This is also a good result because, despite the imperfect load the coax stub continues to perform well. That might not be case with a much higher SWR. Although it is an interesting question, it is not one I'm too concerned about since I design my antennas to have a low SWR over the band segments of interest. Not always, it is true, but it is true enough for my purposes most of the time. I am not aiming for perfection.</p><p style="text-align: left;">One of the reasons why I did the mismatch test was that I have seen it reported that due to the varying R and X values along a mismatched transmission line, the <a href="http://k9yc.com/LocatingStubs.pdf">placement of the stub affects its performance</a>. I now doubt whether that is true. Further testing may be called for, but not now. I can explore it in greater depth another time if I feel so inclined. I'm supplementing my mismatch experiment with a simple diagram. [Too simple, but I didn't want to spend the time making it complete and complex; it is only intended as a guide while following the text.]<br /></p><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgdD4Sx2L6mhP-6uv5IJ_37YWP5Gf5B2b-KurD8HDMYFFSm7hb4rEeznn-yFUTU6jXqdTo3uSfk0bNLv82pXKTc6NFlqqpyI17VjofNv1Ly8zBOixaBfKplwxr53nynwQKb9OLQguskvdOgLDLP2VBOQvhlH4xhlZzkE8o3hdozBKP3srqjSmAxa3OcxyEm/s570/stub_harmonic_reflections.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="267" data-original-width="570" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgdD4Sx2L6mhP-6uv5IJ_37YWP5Gf5B2b-KurD8HDMYFFSm7hb4rEeznn-yFUTU6jXqdTo3uSfk0bNLv82pXKTc6NFlqqpyI17VjofNv1Ly8zBOixaBfKplwxr53nynwQKb9OLQguskvdOgLDLP2VBOQvhlH4xhlZzkE8o3hdozBKP3srqjSmAxa3OcxyEm/s16000/stub_harmonic_reflections.jpg" /></a></div><p style="text-align: left;">After the transmission starts, the wavefront splits at the T connector, half going each way (blue & red). It takes a fraction of a microsecond for the signal to travel down and up the coax stub where it interferes with the signal from the transmitter. In this case it is in phase at the fundamental frequency and out of phase at the even harmonics. </p><p></p><p style="text-align: left;">The fundamental wavefront continues toward the antenna at full power (half + half). The even harmonics go no further because the signal from the transmitter and exiting the stub are equal and opposite and travelling the same direction. Other than a small residual energy that is not cancelled (orange), the antenna behaviour at the harmonic frequencies becomes irrelevant.</p><p style="text-align: left;">Harmonics exiting the stub also travel in the reverse direction, towards the generator (amplifier). It is not cancelled, and the reflection causes extreme standing waves between the stub and amplifier. That is seen by the amplifier as a high SWR at those frequencies. The power in the harmonics is very low so the operating parameters of the amp are unaffected.</p><p style="text-align: left;">The initial leading edge of harmonic energy, having gotten ahead of the signal transitting the stub, will in most cases reflect back from the antenna's high impedance at that frequency, as discussed earlier. It, too, encounters the stub and the same thing happens in the reverse direction as it did in the forward direction. It will eventually dissipate through attenuation and (some) radiation.<br /></p><p style="text-align: left;">The fundamental and harmonic signals can be individually followed and analyzed. They do add in superposition but the harmonics are too weak to measurably affect the total system. From this brief analysis I suspect that K9YC is incorrect about the importance of stub placement on the transmission line.</p><p style="text-align: left;">Stubs are not the only way to attenuate amplifier harmonics, as already mentioned. Let's recap the alternatives:</p><ul style="text-align: left;"><li style="text-align: left;">Coax ½λ shorted stub (relative to the second harmonic): With low loss coax the second harmonic can be attenuated by at least -20 db across the higher band, often better than -25 db, with low insertion loss. The third harmonic cannot be attenuated. The fourth harmonic is attenuated only a few decibels less than the second. Filters can be ganged in series for greater harmonic attenuation.<br /></li><li style="text-align: left;">High power BPF: All harmonics are attenuated. Depending on filter design, the second harmonic can be attenuated by -40 db or better, and higher order harmonics are often attenuated better than -50 db.<br /></li><li style="text-align: left;">High power LPF: Low pass filters filter all harmonics. They are not as complex as BPF but neither can they work as well below fifth order for the second harmonic. The <a href="http://tonnesoftware.com/elsie.html">Elsie</a> model below is an example of a fifth order Chebyshev 40 meter LPF. The marker is at 14.2 MHz. Insertion loss is better than a BPF for a similar or lower component count and can be cheaper if you build it yourself.<br /></li></ul><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiTcXDRLh5PkufERWrLlrUCt2nsS-9mtJoJwIL-b1QEPb5aGxlA4-0E0RmH8qoRpPKIC2WzGvASyeaYAaJh8Z48bn4PAoA7twaWPNoKeh30vBX9hj1kRnRR0KMfR5JXgbZqE0-0cubcJhsYvEXbOtGbv2hs4B6syQaj-dJy9BktlL6yTlgnsb0PLkgzNj1z/s800/elsie_5th_order_hpf_40m_at_14.2mhz.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="457" data-original-width="800" height="366" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiTcXDRLh5PkufERWrLlrUCt2nsS-9mtJoJwIL-b1QEPb5aGxlA4-0E0RmH8qoRpPKIC2WzGvASyeaYAaJh8Z48bn4PAoA7twaWPNoKeh30vBX9hj1kRnRR0KMfR5JXgbZqE0-0cubcJhsYvEXbOtGbv2hs4B6syQaj-dJy9BktlL6yTlgnsb0PLkgzNj1z/w640-h366/elsie_5th_order_hpf_40m_at_14.2mhz.jpg" width="640" /></a></div><br /><p style="text-align: left;">How much harmonic attenuation is enough? In the story at the start of this article the second harmonic was S9+, so it was loud but not louder than a great many signals on 20 meters that morning. That helps explain why I mistook it for another station. Let's see what Acom has to say about their amplifiers. I'll quote from their specs for the <a href="https://www.acom-bg.com/products/amplifiers/acom-2000a-automatic-hf-linear-amplifier">Acom 2000a</a>:</p><p></p><blockquote><p style="text-align: left;"><i>"Classical Pi-L network, all-air coils (no ferrite), and carefully
designed layout of the output tank offer typical harmonic emissions as
low as - 55 dBc (second) and below - 70 dBc (third and above)."</i></p></blockquote><p style="text-align: left;">And for <a href="https://www.acom-bg.com/products/amplifiers/acom-1500hf-6m-linear-amplifier">Acom 1500</a> that I own:</p><ul style="margin-left: 40px; text-align: left;"><li style="text-align: left;"><i>1.8-21.5 MHz - better than 50 dB below rated output;</i></li><li style="text-align: left;"><i>24-54 MHz - better than 66 dB below rated output;</i></li></ul><p style="text-align: left;">That is about as good as it gets since tetrodes in a well-designed amplifier exhibit very linear performance. Grounded grid triodes do a little worse and solid state amp typically do worse yet. It is good practice to choose a solid state amp that has lots of headroom at your intended operating power to ensure maximum linearity. The rollout of DPD (digital pre-distortion) may play a role in removing the harmonics generated by solid state amplifiers by improving system linearity.<br /></p><p style="text-align: left;">I can't do much better for harmonic levels with amplifiers other than the ones I own -- Acom 1500 and Drake L7 -- yet I have problems with harmonics. It won't get better because it is likely that I will eventually transition to solid state amps to allow rapid and reliable band and antenna switching. Based on my experience I will wither have to switch to high power BPF, as almost all the best contest stations have done, or use stubs. The wait for broad deployment of DPD in the shack could be a long one.<br /></p><p style="text-align: left;"><a href="https://va6am.com/">VA6AM</a> makes excellent high power BPF that are used by many contesters of my acquaintance. There are other products of similar quality available. But high power BPF are expensive and in most stations will require heat management and custom switching.<br /></p><p style="text-align: left;">The time has come to try coax stubs in my station. I will start small, and if it is successful I can expand their use. For my antenna switching architecture it is easiest to make a stub for either 80 or 40 meters. The reason is that there is no switching required. My antennas for those bands have <a href="https://ve3vn.blogspot.com/2023/04/auxiliary-antenna-switch.html">auxiliary switches</a> connected to single ports on the 2 × 8 antenna switch where the stub can be conveniently attached. Better, it will be outdoors and out of sight. </p><p style="text-align: left;">I have an ample supply of short lengths of Heliax and connectors from which to make low loss coax stubs. They can finally be put to good use. Assuming all goes well, I can do the same for 160 meters. For 20 meters they will need to be switched, per station, since there are several antennas distributed across several switch ports. As previously discussed, stubs are superfluous on 15 and 10 meters.</p><p style="text-align: left;">I'll try to get the first one done in time for the ARRL DX contests later this winter if I can fit it into my schedule. I may have to make it easily removable between contests because I currently use the 40 and 80 meter antennas on 30, 17 and 12 meters (the WARC bands). The stubs are incompatible with that.</p></div><p></p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com0tag:blogger.com,1999:blog-6207999661586171874.post-33590513716292851972023-12-04T19:59:00.006-05:002023-12-04T21:14:12.697-05:00Post-contest: Silence of the Bands<p>Have you ever noticed how quiet the HF bands are after a major contest? It was true last week after CQ WW CW and it is true again this week after the less popular ARRL 160 meter contest. This is quite different from what I remember decades ago.</p><p>Contesters were a minority back then. There was a lot of conflict on the bands during major contests due to the abundance of conversations, DX hunting, nets and so forth. The HF bands are quieter now. There are several reasons for the change. Since I've <a href="https://ve3vn.blogspot.com/2022/05/radiosport-future-of-amateur-radio.html">discussed this before</a> (as have many others!) I won't repeat them.</p><p>Despite the lower level of HF activity, why are the bands unusually quiet on the Monday morning after the contest? The reason appears to be that a large fraction of today's daily activity is by contesters. They (we) are resting.<br /></p><p>Immediately following a contest that I have little interest in turning on the radio. There is fatigue, chores delayed and an aversion to returning to the air so soon. I am not alone. Unless there's an interesting DXpedition, a 6 meter opening or something else sufficiently attractive to draw me back, the radio stays off. About all I might do is to monitor DX spots for items of interest. </p><p>On Sunday evening after the ARRL 160 meter contest, the lack of DX spotting activity was notable. I recall one period of 30 minutes when there were just a few spots from stations in the eastern part of North America (I usually filter spots from elsewhere). Flipping from band to band showed a blank band map. Tuning the CW segments uncovered nearly no signals at all. </p><p>Activity will soon recover as the contesters rest and recharge. We don't stay away for long. There is no need to suspect an elevated geomagnetic activity level since that does not hurt conditions enough to keep the enthusiasts away. We really have become a hobby where radiosport is a top interest and motivator.</p><p>Of course there are many exceptions, but that does not detract from the point. Digital activity continues, though even that is at a lower level. Those normally absent from the HF bands, such as VHF aficionados and those strictly on FM, likely don't notice. Tinkerers and makers might similarly be unaware. Hams active in SOTA and POTA also seem not to notice, although they may enjoy the brief respite from QRM. Yet it is a phenomenon.</p><p>Is it a problem? Probably not, at least not yet. What it may suggest, however, is that unless radiosport is taken up in a big way by new and younger hams the HF bands will only become more silent in the future. This is already happening to a degree, but a full generational replacement is unlikely. </p><p>While it is a sad development for many of us, the amateur radio hobby will continue to change in the direction set by trends in technology and culture. HF will likely play a lesser role in that future.</p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com0tag:blogger.com,1999:blog-6207999661586171874.post-50360760339060436362023-11-29T22:17:00.002-05:002023-11-29T22:17:45.144-05:00Improving (maybe) the 160 Meter Shunt-fed Tower<p>My <a href="https://ve3vn.blogspot.com/2020/11/160-meter-shunt-fed-tower.html">shunt-fed 140' tower</a> works very well on 160 meters. But it can be made better. With the winter top band season underway, the time has come to do so. While it may seem odd to put the effort into 160 meters when the high bands are consuming the attention of most hams, there are two strong reasons: contests and DXpeditions.</p><p>I would eventually like to achieve additive <a href="https://ve3vn.blogspot.com/2021/06/driving-arbitrarily-spaced-verticals-on.html">gain and directivity</a> by shunt feeding both of my big towers, that is a project for another year. Making each of the verticals more effective are beneficial on their own and for when I proceed with the phasing project. It is time to make the existing vertical better. By better I mean the following:</p><ul style="text-align: left;"><li>Higher efficiency: lower ground loss</li><li>Match: broaden the SWR bandwidth</li><li>Permanence: replace the "temporary" construction with a more robust system</li><li>Arc elimination: lower the voltage across the gamma capacitor</li></ul><p>Lowering ground loss is perhaps the easiest: add more radials. I increased the radial count from 8 to 16. SWR bandwidth and gamma capacitor voltage are both dealt with by increasing the gamma "rod" diameter. Permanence, well, we'll see how I've done. Let's look at each item in turn.</p><p>For convenience of construction and radial placement, I previously placed the radial hub at the base of the gamma rod/wire, positioned ~2 meters from the tower base. I have now moved it to the tower base. </p><p style="text-align: left;"><b>Radial hub</b></p><p>I wrapped the tower with a band of aluminum flashing and stainless ¼" studs to attach radial wires. First I had to move the heavy aircraft cable wrapped around the concrete pillar with a small one on the tower's pier pin base. I have these on both big towers to serve as anchors for antenna work.<br /></p><p><b><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxxOSpGTHDYoh9C16a1VbIpOUlOjvwHxXpfcEIfXpuxgpGmVMGHXPpcyDFn107_HRMLC9GFCxxsEgCr0_4IXwVbd4YWLlWB0aL8I81l730V_b-S1lVsH0iIFH_iaqlonYgvmzuXRJXtJXtlWBWhOEPYh8LXPZhA0hBE7t9PgJS06rY60RX6eUxmdz7ieKL/s480/160m_radial_ring_temp.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="455" data-original-width="480" height="379" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxxOSpGTHDYoh9C16a1VbIpOUlOjvwHxXpfcEIfXpuxgpGmVMGHXPpcyDFn107_HRMLC9GFCxxsEgCr0_4IXwVbd4YWLlWB0aL8I81l730V_b-S1lVsH0iIFH_iaqlonYgvmzuXRJXtJXtlWBWhOEPYh8LXPZhA0hBE7t9PgJS06rY60RX6eUxmdz7ieKL/w400-h379/160m_radial_ring_temp.jpg" width="400" /></a></b>The new radial hub is pretty flimsy, so permanence remains elusive. It is a cheap and easy solution until I see how well the new design works. Tripping on a radial (not uncommon!) bends it out of shape, but it hasn't broken, yet. </p><p>Assuming it works out I'll replace it with a copper band next year. I could easily wrap the base with copper wire and solder the radials on, except that the radials must be removed each spring for the farming season. Mechanical connections makes that activity more convenient.</p><p>The new radial hub consists of a 2" (5 cm) wide strip of aluminum roof flashing (~0.015" thick). It's cheap and I have a lot of it, but it is not very strong. Tripping on a radial puts quite a kink in it. </p><p>I am not too concerned by that weakness. As I said earlier, it's a temporary measure until I am satisfied with the overall design. It'll do for this winter.</p><p>There are a dozen ¼" stainless bolts with the heads on the inside of the flashing. A nut secures each to the flashing and a set of washers and another nut are for attaching the radials. In the picture you can see that I have two radials per bolt.</p><p>To support the radial hub, there are several short lengths of scrap ½" aluminum tubes screwed to it. That keeps it above grade but not so high that the radials are not too exposed to mishaps. A narrow trench has been dug around the concrete pillar that I plan to fill with stone. That's to discourage growth so that I can trim the hay around the tower base without damaging the radials. Yes, I have accidentally cut a few over the years.<br /></p><p><b>Feed point</b></p><p style="text-align: left;"></p><p></p><p><b><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiv3srHn0UTGx6iwxtVnn2mj6NZNRsKyjwUL759GmYA7bNEXcqdMnT9PUGngkUXMOEA91h8EZL7LUh1jAghDiF6dOOtagz3T8yiBP5PdexmdUPrNA2v8y2dPbcc3TaP-FGeo1CV8oVRNT_gIAIJxMFjcb9F7ikYlI1QaicVcXZPY7E6zSXu4ynRZJpnUfO3/s640/160m_decayed_capacitor_box.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="415" data-original-width="640" height="130" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiv3srHn0UTGx6iwxtVnn2mj6NZNRsKyjwUL759GmYA7bNEXcqdMnT9PUGngkUXMOEA91h8EZL7LUh1jAghDiF6dOOtagz3T8yiBP5PdexmdUPrNA2v8y2dPbcc3TaP-FGeo1CV8oVRNT_gIAIJxMFjcb9F7ikYlI1QaicVcXZPY7E6zSXu4ynRZJpnUfO3/w200-h130/160m_decayed_capacitor_box.jpg" width="200" /></a></b>When
I first built the antenna several years ago I used a margarine tub to
hold the gamma capacitor. The intent was that it would be temporary. Of
course it became permanent, as these things always do. As you can see
the elements were not kind to it.</p><p>For the experiment with a cage gamma rod I used another margarine tub. Of course it'll
also be temporary. Or so I hope. </p><p>The new one has one added feature: a
coax connector. It beats the wire nuts covered in plastic and tape that I
used to connect the coax and jumpers to the radials and
gamma wire. The picture below shows the inside, with the gamma capacitor I ended with after tuning (more on this later).<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiuoq4srHLfVp-LmiavVe_iHLDNtIuiBSGJqTBuvXLXd7TWYRLmt5BmwKzG-KZexG-l0a5obnNXwWBAK66TGADoIpfoMvRlc4oO1Ydt-zzKx_NS_Zc0DW6NaQYTpXZNE2Dba9eh_0TcwN3lF-pvmOC6IMxCC-b6VFp4ocxb01s6tkNvXEiJz1yZxrYYrVXN/s600/160m_new_capacitor_box.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="425" data-original-width="600" height="284" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiuoq4srHLfVp-LmiavVe_iHLDNtIuiBSGJqTBuvXLXd7TWYRLmt5BmwKzG-KZexG-l0a5obnNXwWBAK66TGADoIpfoMvRlc4oO1Ydt-zzKx_NS_Zc0DW6NaQYTpXZNE2Dba9eh_0TcwN3lF-pvmOC6IMxCC-b6VFp4ocxb01s6tkNvXEiJz1yZxrYYrVXN/w400-h284/160m_new_capacitor_box.jpg" width="400" /></a></div><p style="text-align: left;">Seriously
though, I do have a permanent feed point system half built that uses
proper components. I can go ahead and finish it now that both CQ WW
contests are behind me.</p><p style="text-align: left;">One
curious effect on the feed point impedance is worth mentioning. When I
had 8 radials the resonant frequency measured in the shack was about 15
kHz higher than that measured at the feed point. That's because outer conduction of the
buried Heliax transmission line, when connected, becomes the ninth radial.</p><p style="text-align: left;">With
16 radials the frequency shift is negligible: what I measure at the
feed point is very close to what I measure in the shack. The transmission line has
less effect on resonance when there are more radials. That is not a
surprise since it was <a href="https://ve3vn.blogspot.com/2018/05/radials-resonant-to-non-resonant.html">what I expected</a>.<br /></p><p></p><b></b><p><b>Radial wire</b></p><p>Each bolt on the radial hub terminates two radials: one of the 8 original and one of the new 8. All are 30 meters long. The original radials are AWG 18 insulated solid copper purchased new. Of the new radials, two are the same and one is stranded. For most of the rest I used wire that I bought at flea markets at bargain prices. They range from AWG 20 hook up wire to AWG 16 electrical wire. When I ran out of wire I used AWG 17 aluminum electric fence wire left over from Beverage antenna construction. </p><p>It's a hodge podge approach that's cheap. Cheap matters since the radials require 500 meters of wire. I was not concerned with wire gauge since the more radials you have the thinner they can be. The reason is that the antenna current is evenly divided among them. However, do not make that assumption for a low radial count such as 4 since they are susceptible to imbalance due to variations in the ground composition and therefore the velocity factor in each. Too thin should be avoided since the wire is easily damaged.<br /></p><p>Power lost due to ohmic loss in the radials declines faster than the radial count increases. That is true due to the power equation <b>P = I²R</b>. When you double the radial count, as I have, the current in each is halved and the ohmic loss is ¼ what it was. Ohmic loss declines with the square of the radial count, all else being equal.</p><p>Of the 16 radials, 3 had to be bent near the end because they ran into the stone wall that surrounds my yard and house. For this many radials the impact on current balance and performance is small and is not nearly as important as having the radials.</p><p><b></b></p><div class="separator" style="clear: both; text-align: center;"><b><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhqpErCvH5J-gQEAd4IqM0jALvDfv88gKG1OGKYaLxI3CdFmACVEsiHhsF2N7rDcQcDg4nzPsWuLeUNH6vwOHPjH9qtgILXneOHPKwyWWIEd9LuCbPaXdupOc6zzUlTWx0zuxEfoYnyT8rJBe9OeOGk4_wUGa5Ulq4vWm4mSIJwhQn1xchWcxv3GJ4JMo6Q/s928/160m_gamma_cage_mosaic.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="527" data-original-width="928" height="364" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhqpErCvH5J-gQEAd4IqM0jALvDfv88gKG1OGKYaLxI3CdFmACVEsiHhsF2N7rDcQcDg4nzPsWuLeUNH6vwOHPjH9qtgILXneOHPKwyWWIEd9LuCbPaXdupOc6zzUlTWx0zuxEfoYnyT8rJBe9OeOGk4_wUGa5Ulq4vWm4mSIJwhQn1xchWcxv3GJ4JMo6Q/w640-h364/160m_gamma_cage_mosaic.jpg" width="640" /></a></b></div><b></b><p style="text-align: left;"><b>Gamma rod</b></p><p></p><p>I perused ON4UN's book and I made an initial trial with two AWG 12 wires spaced 40 cm (16"). The model (see below) suggested that it would work well to broaden the 2:1 SWR bandwidth to 130 kHz. I went ahead and built it with wire scavenged from a 40 year old 40 meter delta loop. It was a great antenna but I have better ones now.<br /></p><p>The upper cage support was made from junk box metal. The brackets that hold the aluminum tube are more than adequate to handle the dead load and the tension to keep the cage taut. I added a support rope as insurance. The pre-drilled galvanized angle is found in almost every hardware store. The multitude of holes ease experimentation with wire spacing.<br /></p><p>Another bit of scrap tube and hose clamps keep the wires in position at the bottom. Rope and brick weights provide tension. Despite the high RF voltage at the bottom of the gamma rod there is no risk of arcing because both wires are at the same potential. This arrangement was to be temporary until tuning was completed but it works well enough that I'll keep it for at least this winter.<br /></p><p>The top of the gamma rod is at 55', 5' lower than the previous 60'. According to ON4UN the tap point is slightly lower with a cage than with a single wire. The model confirmed that but the difference is so small that lowering it was unnecessary. During tuning (see below) I raised it back to 60'.<br /></p><p><b>Model</b></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgAvTpBMa94OqGPZt7LfIqITDRhZDGYyrkXtg8ke59jE-V1s7NRMBccsUF8h43WEPI2ch8FeaW3aD_wjAsezDqkJ-1kiH3Is2vz59PVS2-YjC4hT4ukmkh25LiHHLcAgk7oKN15GPiFGgLdEFh9pkW7riWA2ee6e32NCUxi8apNYPnnd0FNTHov0nC7-TAm/s302/160m_cage_eznec_feed_view.png" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="259" data-original-width="302" height="259" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgAvTpBMa94OqGPZt7LfIqITDRhZDGYyrkXtg8ke59jE-V1s7NRMBccsUF8h43WEPI2ch8FeaW3aD_wjAsezDqkJ-1kiH3Is2vz59PVS2-YjC4hT4ukmkh25LiHHLcAgk7oKN15GPiFGgLdEFh9pkW7riWA2ee6e32NCUxi8apNYPnnd0FNTHov0nC7-TAm/s1600/160m_cage_eznec_feed_view.png" width="302" /></a></div><p style="text-align: left;">The tower is loaded with yagis which make the modelling process difficult. Since including them results in a large and unwieldy model, I substituted a single wire that is the electrical equivalent length of about 58 meters based on an earlier measurement of the tower monopole. The measurement was partly swamped by the ground ESR via the lightning ground rod (~75Ω) but gave a clear signal of <a href="https://ve3vn.blogspot.com/2020/11/160-meter-shunt-fed-tower.html">resonance at about 1200 kHz</a>. That is, the tower plus yagis is approximately an electrical ⅜λ on 160 meters. The physical height of the tower plus mast is 43 meters.</p><p></p><p>⅜λ is an excellent height for a vertical but it is difficult to match. The impedance is quite sensitive to the frequency. For that reason the SWR bandwidth is narrow. It was 70 kHz for the original gamma match. Further, the high inductive capacitive reactance requires a low value capacitor to cancel it and that results in a high voltage at the gamma match feed point. Increasing the bandwidth and taming that high voltage go hand in hand. </p><p>Zooming into the feed point illustrates how the cage gamma rod is modelled. The top of the rod is the same but without the loads. MININEC ground is specified to simplify the model for the purpose of impedance matching; at this point I was less concerned with efficiency. The load in wire #1 is the estimated ESR (equivalent series resistance) of the soil and radial field. The load in wire #5 is the gamma capacitor. The source (feed point) is the circle in the bottom segment of the tower.</p><p>I adjusted the model parameters until I had a 50 Ω impedance. They were closely in line with the tables published by ON4UN. The gamma rod spacing to the tower was 0.7 meters (28"), with a 20 meter high tap point and the aforementioned 40 cm spacing between the cage wires.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZM9auohEcWmL8cvouuQkyFSxj6onm50LbGX-BjZpVPlJLPBuikkYCj86Qx6hXDWWheAfbwNj-pSEV6VHXnJcXP1vrwtgo3U3l67IN9tFxkKFxrVCX5Ju63yqr6lqFMFfExXw0SMQPPCYqB77XZjusXORm2RX1K_e6d_7NUcbSd1T-QvgV_PF3EbdIlWFU/s696/160m_cage_eznec_swr.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="240" data-original-width="696" height="221" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZM9auohEcWmL8cvouuQkyFSxj6onm50LbGX-BjZpVPlJLPBuikkYCj86Qx6hXDWWheAfbwNj-pSEV6VHXnJcXP1vrwtgo3U3l67IN9tFxkKFxrVCX5Ju63yqr6lqFMFfExXw0SMQPPCYqB77XZjusXORm2RX1K_e6d_7NUcbSd1T-QvgV_PF3EbdIlWFU/w640-h221/160m_cage_eznec_swr.png" width="640" /></a></div><p></p><p>The SWR bandwidth closely matches the 130 kHz predicted from the tables in ON4UN's book.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjlyRCixoidrLtbrhsAiPIk3zgzfvtUtuAQoI4zJ4mlI3fYW1aZ_cGgDeUzvgCTrAoxO3GQrbvuH3Ld4kjCc8WzchCDDB7D6_va9LeuIHPQvyvSFFHbIrLOT_HydqRLBLRR7MKipXSF5-m_yGgsyCz41L342H3yp4RmgffJ8-_ENRbyKrCWvvWwdQS8jfyq/s440/160m_cage_eznec_loads.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="333" data-original-width="440" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjlyRCixoidrLtbrhsAiPIk3zgzfvtUtuAQoI4zJ4mlI3fYW1aZ_cGgDeUzvgCTrAoxO3GQrbvuH3Ld4kjCc8WzchCDDB7D6_va9LeuIHPQvyvSFFHbIrLOT_HydqRLBLRR7MKipXSF5-m_yGgsyCz41L342H3yp4RmgffJ8-_ENRbyKrCWvvWwdQS8jfyq/s16000/160m_cage_eznec_loads.png" /></a></div><p style="text-align: left;">At 1000 watts the gamma capacitor voltage for the cage gamma is about half of what it was with a single wire. It is still high -- that's unavoidable in this situation -- but far safer and easier to construct with components found in my junk box.</p><p></p><p>When I reached this point I was sufficiently confident to proceed with building and installing the cage gamma rod. Before we turn to that let's first discuss an alternative model of the antenna.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjz554C3u2ybozOggAbImLve_jiwa-vybVQP1fP1oofk8ktXpwUSMhJtshCzl6-7w1c1IAm9-75f27LGdH2JyR18wIyhk-PbgbVsJrSWRHb9CktQbTdtZKYnssl8Hsb3ZzqCKsdgC088GDP7oZcLFalqv1SWKh1cCl_xu_pmdK0xHQmZK7emk7TKkpojNNn/s710/160m_lr20_shuntfed_8vs16_radials.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="405" data-original-width="710" height="365" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjz554C3u2ybozOggAbImLve_jiwa-vybVQP1fP1oofk8ktXpwUSMhJtshCzl6-7w1c1IAm9-75f27LGdH2JyR18wIyhk-PbgbVsJrSWRHb9CktQbTdtZKYnssl8Hsb3ZzqCKsdgC088GDP7oZcLFalqv1SWKh1cCl_xu_pmdK0xHQmZK7emk7TKkpojNNn/w640-h365/160m_lr20_shuntfed_8vs16_radials.jpg" width="640" /></a></div><p style="text-align: left;">In addition to the basic model, I also built one that includes additional detail. The <a href="https://ve3vn.blogspot.com/2020/12/lifting-yagis-15-and-20-meter-stacks_11.html">20 and 15 meter yagis at the top</a> were modelled as single wires that are about 30% longer than the booms. That brings the tower resonance in accord with the measurement of about 1200 kHz. The lower yagis of the stack are not included since they typically contribute little to the total capacitive loading. I may add them later to confirm that considering that the lower 20 meter yagi is not far above the gamma rod tap point.</p><p></p><p>I constructed radial systems with 8 and 16 radials over EZNEC real medium ground. To keep them out and off the ground (not allowed with NEC2) they are positioned 10 cm high. The difference is slight in comparison to on-ground radials. It is a common workaround for modelling radials with NEC2.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgFpY7IkBfDkx2IOs44QNvDpaZYxjxMjQn0TBQle-VNnoyEwjQs9v4iQbJao9zxSOXL8X8MrqApf_4Pg9Abl1GDs2lywoPK2EU6H24p1qg5E1yIvL0zhhDY8XULlym31es9ByaVvsnjVhei2RZ57Rac24oVaPWYJSNdXMQN-nupjbMj767Cm5cpFjt43ZMo/s652/160m_cage_being_tuned.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="652" data-original-width="480" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgFpY7IkBfDkx2IOs44QNvDpaZYxjxMjQn0TBQle-VNnoyEwjQs9v4iQbJao9zxSOXL8X8MrqApf_4Pg9Abl1GDs2lywoPK2EU6H24p1qg5E1yIvL0zhhDY8XULlym31es9ByaVvsnjVhei2RZ57Rac24oVaPWYJSNdXMQN-nupjbMj767Cm5cpFjt43ZMo/w295-h400/160m_cage_being_tuned.jpg" width="295" /></a></div><p style="text-align: left;">The efficiency comparison is interesting because it is less than 0.1 db. However, this is likely not really true. NEC2 is really not up to the task of accurately modelling ground loss and I've run into this discrepancy many times before. </p><p style="text-align: left;">The experiment measurements by <a href="https://www.antennasbyn6lf.com/design_of_radial_ground_systems/">N6LF</a> and others for 160 meter radial systems suggest that the expected gain improvement is between 0.5 and 1.0 db. That may seem tiny but it can make a difference on marginal propagation that is routine on top band.</p><p></p><p>I am not equipped to measure field strength. Instead I measured the feed point impedance. In the initial configuration for the cage gamma rod, the impedance dropped from about 40 to 30 Ω. Although significant, the true improvement in ground ESR is not 10 Ω because this is the impedance as transformed through the gamma match. I did not reverse the calculation in an attempt to pin down the actual change.<br /></p><p><b>Tuning</b></p><p>At right is the tuning setup for the cage gamma. When the picture was taken the tap point was at 55' so the cage wires reach almost to the ground. I was using a large capacitor since, as discussed above, the model led me to expect the voltage to be about half that as before. That corresponds to a low capacitive reactance: Xc = 1/(2πfC)<br /></p><p>After several iterations of adjusting the gamma rod spacing I achieved a 50 Ω match.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjqGt1Q3WJ991EDYwNK50eZowqUrNxWkTenP-ouOoVWijZo3h101V4jsxjZ0h87vtRkOT8KIXEzct27wygpm87Sbaq2O672gXlt3Dr6sa-SbI3nziiGZP_0jdzN904qVRQJwSPXzYJTVLd72_lCLHfhUmYqoSa3ezVtd_NfcvnlMiH7HhKP4sagjxSLjbPn/s600/160m_cage_prototype_swr.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="336" data-original-width="600" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjqGt1Q3WJ991EDYwNK50eZowqUrNxWkTenP-ouOoVWijZo3h101V4jsxjZ0h87vtRkOT8KIXEzct27wygpm87Sbaq2O672gXlt3Dr6sa-SbI3nziiGZP_0jdzN904qVRQJwSPXzYJTVLd72_lCLHfhUmYqoSa3ezVtd_NfcvnlMiH7HhKP4sagjxSLjbPn/s16000/160m_cage_prototype_swr.jpg" /></a></div><p style="text-align: left;">There are two possible reactions to this beautiful SWR curve:</p><p></p><ol style="text-align: left;"><li>Wow! Mission accomplished.</li><li>No way! The antenna physics don't permit this.</li></ol><p>I was suspicious but enough of an optimist that I was leaning towards the first reaction. I constructed the prototype high voltage gamma capacitor in the margarine carton and hooked it up. That evening I gave it a try. None of the European stations I called could hear me or could not hear me well enough to copy my call. Yet they were not weak and I usually have no trouble working them. It was then that my reaction changed to the second one and I began searching for answers.</p><p>It didn't take long to discern the likely problem. The next morning I looked over the antenna and confirmed my suspicion. When I connected the radial hub to the ground rod I forgot to reconnect the wire from the tower to the ground rod. The only path for antenna currents to complete the circuit from the base of the tower to the radials and coax shield was <a href="https://ve3vn.blogspot.com/2020/12/160-meter-vertical-ground-disconnection.html">via the soil</a>. The loss was therefore excessive. In other words, the ground loss dominated the feed point resistance.</p><p>When I restored the missing connection the beautiful SWR curve vanished. To cancel the inductive reactance the capacitance had to be greatly lowered. The impedance was approximately 21 + j0 Ω. That's far lower than what's acceptable.<br /></p><p>Unfortunately I could not raise the impedance to 50 Ω. The best that I achieved was in the vicinity of 30 Ω. It was after several fruitless trips up the tower to adjust the spacing between the tower and gamma rod that I restored the tap point to its original 60'. That, too, helped very little. Worse, the further outboard I placed the gamma cage the capacitor value declined and the SWR bandwidth narrowed. What I ended up with was little better than what I had before.<br /></p><p><b>Defeat</b></p><p>The impedance at 1850 kHz was 41 + j0 Ω and 2:1 SWR bandwidth of 80 kHz. With contests coming up and many other projects on my list I reluctantly stopped work on the antenna. It's good enough for this winter. The extra radials give my signal a boost and the SWR is easily dealt with by the amplifier. The rig's ATU is not needed across the DX segment of the band. It is needed when the I go outside that narrow range during contests when I don't use the amp.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg08n79bZuyN7uxe8IUrr8CTaxo-7RD1CEhyphenhyphensUJ4jrNj9iru2Xp8rVLGofOc5uGt8IhzOE-t4rKKchxqCl6WZFPauW-Vv87g9MgdcFgSNcsNlKQxzcYah5vj_i0uO4JwPEi5AIiPW64Vh0TtpJfZIrWOmn2S9cEuqHhWtlG5TkCCI7FPm904pcy4cul7GFD/s194/160m_57m_0.375wl_current.png" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="194" data-original-width="97" height="194" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg08n79bZuyN7uxe8IUrr8CTaxo-7RD1CEhyphenhyphensUJ4jrNj9iru2Xp8rVLGofOc5uGt8IhzOE-t4rKKchxqCl6WZFPauW-Vv87g9MgdcFgSNcsNlKQxzcYah5vj_i0uO4JwPEi5AIiPW64Vh0TtpJfZIrWOmn2S9cEuqHhWtlG5TkCCI7FPm904pcy4cul7GFD/s1600/160m_57m_0.375wl_current.png" width="97" /></a></div><p style="text-align: left;">I returned to the model to try and discover what might be happening. I can't say for certain despite learning a few new things about the antenna's behaviour. </p><p></p><p>The first thing I learned is that a gamma match on a ⅜λ vertical does not react the same way as on a vertical that is closer to being ¼λ. The reason is that the impedance <i>decreases </i>as you move upward because the current node is ⅛λ above ground. That is about 20 meters in this case. With the tap point at that height, moving up or down increases the impedance. It is then transformed by the transmission line formed by the tower and gamma rod to what is measured at the tower base.<br /></p><p>I confirmed the impedance behaviour with the simple model shown at right. The vertical wire is 57 meters long and is directly connected to MININEC ground. Peak R of more than 140 Ω occurs at 20 meters height. It is about 100 Ω at the base. I then performed a sensitivity analysis by varying the height in 1 meter steps. A 1 meter change in either direction changed R by ~10%. That's a lot!</p><p>Changing the antenna length by 1 meter in the model with the gamma match and cage caused large swings in both R and X components. Clearly the tuning is critical. It is possible there's a tap point further up the tower that will result in a 50 Ω match. Unfortunately that will bring the cage gamma rod close to the <a href="https://ve3vn.blogspot.com/2020/12/lifting-yagis-15-and-20-meter-stacks_11.html">lower 20 meter yagi</a>, and the possibility of the gamma rod threading between the elements. I'd like to avoid that if possible even though interaction ought to be minimal.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgEXp1rrfFUs0hhv4iWXTZOkaWMsIReOreQwWV4K1X-ZN5yRZ5Tmqi62Tu39-i1j_DjDI6lcIJhQhQnocYEFajiCEBUfUqaVjYRdXhmRj1hzX6OHgm-rdTnCFkzhunnFDmic4w_IEi4mLuOqbzgaTErU7yjvPW9w_bYQvWMJ2KRTWBHNdJBbhtCTVc8cMWo/s640/160m_cage_gamma_poor_swr.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="373" data-original-width="640" height="373" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgEXp1rrfFUs0hhv4iWXTZOkaWMsIReOreQwWV4K1X-ZN5yRZ5Tmqi62Tu39-i1j_DjDI6lcIJhQhQnocYEFajiCEBUfUqaVjYRdXhmRj1hzX6OHgm-rdTnCFkzhunnFDmic4w_IEi4mLuOqbzgaTErU7yjvPW9w_bYQvWMJ2KRTWBHNdJBbhtCTVc8cMWo/w640-h373/160m_cage_gamma_poor_swr.jpg" width="640" /></a></div><p style="text-align: left;">Clearly this antenna is more difficult to match with a gamma match than I expected. What I measured is not what I discovered in my cage gamma rod model or what I read in ON4UN's book.</p><p></p><p>That's all the time I have for the 160 meter antenna this season. I was already irritated that I missed the W8S Swains DXpedition appearances on 160 meters while I was in the midst of trying to resolve this mess. I likely would have been able to work them. </p><p><b></b></p><p style="text-align: left;"><b>Planning for the next round</b></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiQ3Gqj_B4k_pf9VTqMTpIv7GM4vcjf5hQDg4iR8r41-MqOUPiBURAH4GIq521UgsP6mEiHh8D33ADsShiNfaVxqrJjwzlslGbZ_tmNgOJM5UJoDoEZWwhk7IL8UWeeP974uOHj75NZn99OWI8NjHMpiA6D5TVk8eLBixLcMFPfVfQraqACzERLnv-Oackr/s728/160m_gamma_connecting_tube.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="728" data-original-width="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiQ3Gqj_B4k_pf9VTqMTpIv7GM4vcjf5hQDg4iR8r41-MqOUPiBURAH4GIq521UgsP6mEiHh8D33ADsShiNfaVxqrJjwzlslGbZ_tmNgOJM5UJoDoEZWwhk7IL8UWeeP974uOHj75NZn99OWI8NjHMpiA6D5TVk8eLBixLcMFPfVfQraqACzERLnv-Oackr/s16000/160m_gamma_connecting_tube.jpg" /></a></div><p style="text-align: left;">I am not so committed to the gamma match that I wouldn't throw it away and try something different. My options are limited since the tower is grounded. </p><p></p><p>The only one that might work is an omega match. An extra capacitor is needed, and the best it can do is shift the impedance match from 40 Ω to 50 Ω. The bandwidth will not be improved and the voltage will remain high.</p><p>The alternative is to insert a switched L-network for the higher frequencies. I could then optimize the gamma match for 1810 to 1860 kHz (SWR better than 1.5). That addresses 90% of my needs. For contests where the activity runs up to 1900 kHz or higher, a switched L-network can lower the SWR up to at least 1900 kHz. The enclosure I plan to use is large enough to accommodate the gamma capacitor, an L-network and more.<br /></p><p><b>To be completed</b></p><p>With the ARRL 160 meter contest coming up fast, I limited myself to an improved connection between the gamma rod and capacitor. It's cumbersome due to the 3 meter gamma rod spacing at the base (it's 2 meters at the top of the rod). </p><p>Using an aluminum tube makes it easy to adjust the spacing without have to cut or add wire. The ABS pipe on the tower isolates the high gamma match voltage while allowing easy adjustment of the gamma rod spacing.</p><p>After the contest I'll take the antenna offline to move the gamma capacitor to its new enclosure. I will also take the opportunity to "rough in" the components for an L-network to lower the SWR higher in the band. Although I have no plan to add it this year, I want to make it easy to do next year.</p><p>I'll continue to contemplate and research the conundrum I ran into with gamma tap point and gamma rod spacing. I'd like to understand the problem better regardless of whether I install a switchable L-network.</p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com0tag:blogger.com,1999:blog-6207999661586171874.post-13585034400845839382023-11-21T10:43:00.000-05:002023-11-21T10:43:23.949-05:00On Becoming a Big Gun<p>Over the years I've operated from all kinds of stations: big and small; QRP and QRO; portable or mobile; wire antennas or stacked yagis; noisy urban environment or quiet rural. But until recently I've never really built and operated a so-called "big gun" station. I've operated the big stations of others in the past, mostly in contests, but never before could I wake up in the morning, turn on the rig and be able to put out a big signal. It's convenient and it has become routine.</p><p>I don't have the biggest station. It's big but there are many that are bigger. That said, there's little doubt that I'm now a member of the 1% (on HF). Many hams love to visit or look at pictures of big towers and antennas even though they'd never try to do it themselves. It takes a lot of commitment and is wildly incompatible with the lives of all but a few. You have to be in a position to do it and you must really really want it. </p><p>Even then it's a big decision. You not only have to build the station, you must also maintain it. There are also improvements to be made to retain your big gun status, if that's your objective. It's a long term commitment. Most are content to get a vicarious thrill from the efforts of others while enjoying the stations within their means and that don't interfere with their lives.</p><p>Now that I've built this station it is interesting to see how it affects me and my operating style. There are differences and similarities; some things change while others do not. Consider this a newly minted big gun's perspective on what it's like being one.</p><p><b>Overwhelming force</b></p><p>This is perhaps what first comes to mind when thinking about big gun stations. There are <a href="https://ve3vn.blogspot.com/2013/03/tricks-of-trade.html">pile up</a> and contest techniques that I need less. Very often I can jump into a pile up on a rare DX station or contest multiplier, send my call once and log them. That certainly requires favourable propagation and that the called station infrequently changes their listening frequency. It doesn't matter how powerful your signal might be when they're listening elsewhere. You must still <a href="https://ve3vn.blogspot.com/2014/10/pile-ups-zig-vs-zag.html">find the sweet spot</a> to make your call.<br /></p><p>In a major contest it can be difficult to find a clear frequency to run. When you find one there will be others trying to "muscle in" from time to time. In rare cases it's a deliberate attempt to steal the frequency. More often another big guns clicks on a temporarily blank spot on the spectrum map (while I'm listening, not transmitting) or doesn't hear me because we're in each other's skip zone.</p><p>In the past I would find it difficult to defend the frequency. Now I can. To use a hockey analogy, when you get in a tight spot you put up your elbows to keep others out of your way. Instead of having to QSY it is usually sufficient to keep CQing. They will soon disappear. Although I don't use my muscle to intentionally steal another's run frequency, unintended conflict can occur anyway. For example, when I get no reply to a "QRL?" I wait a few seconds and launch a CQ.</p><p>This next point is you might not expect. I sometimes feel shame when I jump into a pile up and push through with my big signal to quickly make the QSO. Yes, I still do it but outside of contests I feel a little uncomfortable jumping to the front of the queue ahead of many others who have invested more time and effort into making that contact. It doesn't seem fair. </p><p><b>Attracting pile ups</b></p><p>Many hams are attracted to the strongest signals on the band. The weak signals are passed over because they're more difficult to copy and there is less prospect for a conversation. Yet those weak ones may be rare DX or contest multipliers. </p><p>When I call CQ on any band open to a populated area -- most often Europe -- I will quickly attract many callers. That happens on any day, not just in contests. There are many big guns who love the attention and thrive on it. I do not. Pulling call signs out of a pile up can be hard work and there's pressure to work them all. Of course I can't because I don't spend all my time operating. Without exercising discipline, you will find yourself constantly running. That's necessary in a contest, so I do it despite <a href="https://ve3vn.blogspot.com/2017/03/i-hate-running.html">not liking it that much</a>.</p><p>For ordinary non-contest operation I tend to call others rather than CQ. I find it more relaxing because there's less of a time commitment. Even then I will often sign off from the QSO with a quick note that I am QSYing. When I don't there is a good chance that several stations will call me. They don't know it isn't my frequency.<br /></p><p>When I choose to run, the pile ups can be immense. VE3 may be one of the most common prefixes on the planet, yet they still call. Since I don't do it often outside of contests, non-contesters, especially on SSB, are occasionally surprised to discover that we've never worked before. It is unusual to hear a ham with a big signal that they've never met before. We tend to stand out. </p><p>Most hams just want to talk and a big signal is very conducive to that. Those with simple antennas and low power have learned from experience that it is easier to contact a big station than a small one. I try to accommodate them because I know what it's like. I've been there. I honestly enjoy pulling their weak signals out of the noise and making the contact. When they're QRP it's even more fun.<br /></p><p><b>Satisfaction</b></p><p>A surprising number of North American hams are wealthy or have ample funds to fund their hobbies. That is not too surprising since the majority are boomers and they (we) are the wealthiest generation in human history. I am not wealthy but I am free to spend what I have on what I want. For me that means a big gun station.</p><p>When you have the money it is a simple matter to contract out the work to build the towers. You pay someone else to do the hard physical ground work and then buy antennas, shack equipment and all the peripherals. That is, if you have a family or professional situation that allows or indeed supports your big gun aspirations. Many will spend less than their means to do the best they can with their retirement property and leave the bulk of their money for other things and to support their families.</p><p>When you hire others to build your dream station, does that lead to satisfaction? For many, the answer is yes. The business of aluminum, steel, concrete and silicon is a chore that must be overcome before the fun of operating begins. There is nothing wrong with that, but that approach would not satisfy me. I feel satisfaction when I've done the work: planting and building big towers; designing, building and raising large antennas; and designing and building control systems. </p><p>Many big guns must feel the same way. They stay involved in building their stations to the extent of their abilities and resources. It is rare that no professional help is hired for part of the build. For example, excavation and cranes. On the Bell curve of personal involvement I'm at the tail end where my involvement is maximized. That puts me in the minority of big guns. It's a fat tail so the minority is quite large. There are many station builders that labour behind the scenes because only those closest to them know what they've done. Others garner the recognition by winning contests from their stations.<br /></p><p><b>Guest operators</b></p><p>Which bring me to guest operators. Builders gain satisfaction from building -- I understand that well. They may also enjoy the achievements from operating the station. It just doesn't have to be them doing all the operating.</p><p>I am a middling contester and DXer. Despite my enthusiasm, I am not especially talented and I rarely strive to win. I practice the skills needed to <a href="https://ve3vn.blogspot.com/2021/12/5000-qsos.html">excel and fully exploit</a> my station's capabilities. However, I'll never be a great contester, nor do I particularly care. As I said in an earlier <a href="https://ve3vn.blogspot.com/2021/11/cq-ww-ssb-soasb15-hp.html">article</a>:</p><blockquote><p><i>"It is not enough to put up big towers and antennas to do well in a
contest. You not only have to know how to use them to best effect, you
must also be skilled at running, SO2R, hunting stations and have a keen
eye on DX openings that can be marginal at best with small antennas at a
lower height. I have much to learn and relearn."</i></p></blockquote><p>I <a href="https://ve3vn.blogspot.com/2018/10/dxcc-remaining-40.html">track</a> the countries that I've worked and confirmed but I've <a href="https://ve3vn.blogspot.com/2016/05/dxcc-and-me.html">never applied</a> for DXCC. For anyone who has been reading this blog for a while it should be obvious that I get most of my satisfaction from building the station. A further satisfaction is inviting others to operate, whether it be for a contest or just for fun. </p><p>It came as a surprise that many of my friends who have helped me the most with building this station decline the invitation. They prefer their own stations, even if they're small ones in a crowded and noisy urban or suburban setting. I have come to understand that: there is more satisfaction from operating from one's own station, no matter the circumstances.<br /></p><p>Many big gun stations outside of the US and Canada are club stations. The clubs may be associated with institutions, a property owner and a group of supporters/operators, or a club of peers. Here the big gun stations are almost always privately owned, like mine. Guest operators may come and go but station building and maintenance is solely the responsibility of the owner. </p><p>There are also big gun stations that can be rented for on-site or remote operating. Many partake of that opportunity. As long as you don't overdo it, it is less expensive than building your own. You pay to operate from a station someone else built and you avoid major commitments. It's a business transaction.<br /></p><p>A private station rarely has a padlocked gate. Guests operators are regularly welcomed to join a team for contests or for single-op contests and events.<br /></p><p>I recently held my <a href="https://ve3vn.blogspot.com/2023/11/cq-ww-ssb-m2.html">first multi-op contest</a> and there will be more. They get to enjoy operating the station and I get the satisfaction of building a team and seeing them enjoy themselves. I get a lot of satisfaction from it.</p><p><b>Propagation</b></p><p>Every ham operates at the whim of propagation. No amount of steel and aluminum is enough if nature doesn't cooperate. A 10 db edge over other stations can't compete against 100 db or greater swings in signal strength due to the vagaries of propagation. Big guns and little pistols share the same fate.</p><p>As I've discovered many times, lesser stations that are not far away will often have a large propagation advantage over a variety of paths throughout the day. That, too, can render a big gun station impotent. I am far enough north that even stations near Toronto (300 km to the southwest) regularly beat me in the pile ups. The difference is greater just a little to the south in the northeastern US. </p><p>I really can't complain too much. When I started in this hobby half a century ago I was a VE4, and that was a dreadful location from which to DX and contest. The propagation to Europe and most of Asia had to pass the gauntlet of the auroral zone. </p><p>Not long after moving to VE3 over 40 years ago I often considered moving back to VE4 for reasons of friends, family and culture. Had I done so there would have been little incentive to build a big gun station. You can't fight propagation. Since DX propagation is far better here the incentive exists.<br /></p><p><b>Retro operating</b></p><p>With a large antenna system I often don't need or use an amplifier. The amplifier is turned only in certain circumstances: difficult DX pile ups; some contests; for contest practice; and challenging propagation on 6, 80 and 160 meters. I typically leave the amp on after its intended use in case I decide to make further use of it even when it isn't strictly necessary.<br /></p><p>Not only do I leave the amplifier off, I will often increase the challenge by <a href="https://ve3vn.blogspot.com/2023/03/big-gun-qrp-in-arrl-dx-ssb.html">operating QRP in contests</a>. It's good ongoing practice to ensure that I don't lose my DXing skills. Besides, I still love low power operating. It always puts a smile on my face when I make a difficult DX contact or I do well in a contest with QRP. Of course the antennas have something to do with that! Nevertheless, it is a lot of fun to work DX while putting 5 watts into a big antenna.</p><p>That's what I mean by "retro" operating. When being a big gun becomes too routine or easy, I deliberately challenge myself. Other than QRP, I may use one of my smaller antennas or an antenna pointed in the wrong direction to increase the challenge in a pile up. Although I no longer want to be limited by low wire antennas and QRP -- since I'd <i>have to</i> operate that way all the time -- I like variety and challenges. </p><p>Having it easy all the time diminishes one's skills and interest. To be blunt: being a big gun can be boring if you don't watch yourself. I'm a big gun now but don't be surprised if the next time you hear me on the air that you can barely copy my signal.</p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com0tag:blogger.com,1999:blog-6207999661586171874.post-38146693086022911462023-11-09T21:20:00.001-05:002023-11-09T21:21:11.156-05:00CQ WW SSB: M/2<p>At long last I've fulfilled my plan to host a multi-op. The occasion was CQ WW SSB, which is arguably the most popular contest of all. I was not keen to do it single op since phone contests are not my favourite, and I was so close to being ready to host a multi-op. I recruited a few friends living nearby -- Dave VE3KG, Vlad VE3TM, Greg VE3PJ -- and circled the weekend on my calendar. The deadline spurred me to deal with several critical items on my to-do list:</p><ul style="text-align: left;"><li><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEimoUSYmNw1FEq8ws2w_futupgOoHqAygK_8wSNuKT4W1qbq5VDCbQnXjz8y_tgyL2hQ6TWQvuEf4-FP3we75WD95PNfbyeoOEEoOItoLhB_h9WSKRL5Pez12brl4AkFXt3-KCVKIZ8VaWHvLtRSHumzOBuAXicJySGvDyBYxM70spsDH2FX1Y59W2BxuVC/s469/cqwwssb2023_raw_m2.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="469" data-original-width="237" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEimoUSYmNw1FEq8ws2w_futupgOoHqAygK_8wSNuKT4W1qbq5VDCbQnXjz8y_tgyL2hQ6TWQvuEf4-FP3we75WD95PNfbyeoOEEoOItoLhB_h9WSKRL5Pez12brl4AkFXt3-KCVKIZ8VaWHvLtRSHumzOBuAXicJySGvDyBYxM70spsDH2FX1Y59W2BxuVC/s16000/cqwwssb2023_raw_m2.jpg" /></a></div><a href="https://ve3vn.blogspot.com/2023/10/new-rig-icom-7610.html">New rig</a></li><li>New computers</li><li>Updates to the station automation software</li><li>Upgrade the 160 meter antenna</li><li><a href="https://ve3vn.blogspot.com/2023/10/rearranging-yagis.html">Move and raise yagis</a> to improve effectiveness on the high bands <br /></li><li>Arrange the <a href="https://ve3vn.blogspot.com/2023/09/new-operating-desk.html">operating desk</a> to accommodate two operating positions</li><li>Clean the house and stock the fridge and freezer with food <br /></li></ul><p>My main objective for the contest was for all of us to have a good time. From my friends' feedback it seems that I exceeded that objective. Incrementally building this stations over a <a href="https://ve3vn.blogspot.com/2016/10/welcome-to-fn24br.html">7 year span</a> I had lost sight of what it's like for those with average stations to discover that they've become a big gun and can have endless runs of DX. As one of them told me after the contest: "I had a blast!" </p><p>Although we had just 4 operators for a 48-hour contest in the M/2 category, there was never an empty seat. It was difficult to pry an operator out of the chair to give one of the others a chance. Log statistics show that I had the lowest number of contacts: 1100 out of 7000. It was my plan to be available to guide the others to familiarize them with the station and to use the antennas effectively. I can't do that while I'm operating.<br /></p><p>Our placement among the M/2 raw scores is quite good. We'll see how we did after log checking is complete and the results announced next year. I'm hoping we didn't make too many logging errors. Typos and more are a worry when the focus is on serving the pile up and keeping the rate high. </p><p>Not all of the experience was positive. On the way to running up a pretty good score we encountered a variety of difficulties. However, none dampened our enthusiasm and the impact on our score was modest. I should be thankful that so little went awry.<br /></p><p><b></b></p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEifL2Pliec1VVyaYrgTHqdpJlM6in30bLXr3YCLH-CT0a3foUVPlZ3HMQKrK-snx33ScHKhW7iNMz9FoBUCRg1FolP7QDbexYaLK8MjIaok9dMLvka-6mu91-ZM87MwwZcSYB7ktnhj8kDdqZMb5LnAN4jjvNtZToV_yVrMi3ZRsx8IkO8uxCRMnyDrYqeh/s842/cqwwssb_operators.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="354" data-original-width="842" height="270" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEifL2Pliec1VVyaYrgTHqdpJlM6in30bLXr3YCLH-CT0a3foUVPlZ3HMQKrK-snx33ScHKhW7iNMz9FoBUCRg1FolP7QDbexYaLK8MjIaok9dMLvka-6mu91-ZM87MwwZcSYB7ktnhj8kDdqZMb5LnAN4jjvNtZToV_yVrMi3ZRsx8IkO8uxCRMnyDrYqeh/w640-h270/cqwwssb_operators.jpg" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Photo credit: VA3UMM<br /></td></tr></tbody></table><div class="separator" style="clear: both; text-align: center;"><b></b></div><b></b><p style="text-align: left;"><b>The good</b></p><p></p><p>I suppose the most notable good thing is that nothing went terribly wrong. There was a lot that could have gone wrong that didn't. That's a success. Here's a sampling of what didn't go wrong:</p><ul style="text-align: left;"><li>No power outages</li><li>No equipment failures</li><li>No empty seats due to operator fatigue, disinterest or other issues</li><li>Propagation was excellent on the high bands and average on 80 and 160 </li><li>Very little inter-station interference<br /></li></ul><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhj_YTGMpbH1sGx07sOf2PSVOsMrbMMglHAHchWse0mxEuNnzcHqmZq7uFnHEk82UIE_uh9J6GAteT2Gaa7D4x_xjQZDcX3i0j0rZih7E-V9W4AI_F1ytEaIVjiP9eDmpA62LZW7fzeRPC7jKWJ_V_RLQt34flDhrCASjONuRcYvgYv5jSCIq0pSFr9tcMy/s600/pc_for_automation.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="409" data-original-width="600" height="272" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhj_YTGMpbH1sGx07sOf2PSVOsMrbMMglHAHchWse0mxEuNnzcHqmZq7uFnHEk82UIE_uh9J6GAteT2Gaa7D4x_xjQZDcX3i0j0rZih7E-V9W4AI_F1ytEaIVjiP9eDmpA62LZW7fzeRPC7jKWJ_V_RLQt34flDhrCASjONuRcYvgYv5jSCIq0pSFr9tcMy/w400-h272/pc_for_automation.jpg" width="400" /></a></div><p style="text-align: left;">That's quite good since so much is out of our control during a contest. I have some spare equipment but there is no backup electrical generator to run two high power stations and associated devices. The utility (Hydro One) seems to have been getting better at keeping the power on in this rural area. They also respond well to reports of noise due to faulty equipment. We can hear a pin drop on the other side of the world, and that's great for pulling out the many small signals responding to our big signal.</p><p></p><p>Multi-ops require one computer per station. Since I use N1MM+ those computers are Windows PCs. Inexpensive refurbished Win10 PCs are widely available and I now have 3 of them. Since they use SSD for non-volatile storage they boot quickly and perform well. All PCs have Wi-Fi, built-in or with a USB dongle. </p><p>For the PC running the antenna selector UI (user interface), I plugged in an ancient display and mouse from a defunct XP machine. This is a workaround until I have a touchscreen for each operator. I tried it with two mice (one per operator) so shorten the reach but the PC didn't like that for some reason. You can see the full <a href="http://ve3vn.blogspot.com/2023/10/new-rig-icom-7610.html">multi-op desktop</a> in an earlier article.<br /></p><p>Networking was a breeze. I worried about it unnecessarily before setting it up. A friend told me how easy it was with N1MM+ and so it was. It was so easy I thought I'd done something wrong. Within minutes I had the station PCs communicating with each other and synchronizing logs. </p><p>A third PC hosted my home brew antenna selector UI (user interface). I placed the (ancient) display and mouse for it between the operating positions, along with the controllers for the 5 rotators. I connected two mice to shorten the reach for the operators but the PC didn't like that. The mouse is a workaround until I have a touchscreen for each operator. I was not surprised to discover a few bugs in my software when I turned on N1MM+ networking for the first time. They were quickly resolved.<br /></p><p><b>The bad (where there's room for improvement)<br /></b></p><p>I can summarize the problems in a very short list:</p><ul style="text-align: left;"><li>Antennas</li><li>Amplifiers</li><li>Control</li><li>Multipliers <br /></li></ul><p>The biggest problem with the <u>antennas</u> is that there are so many. I am used to them but the others were not. There are 3 antennas on the high bands, and really 4 when you split the stacks. Some are fixed and some are rotatable. Further, the two tri-band yagis must be shared and each may be unavailable when the other operator is using it. The problem was worst during times of day when we could not run Europe or the US and it was necessary to try various propagation paths in the hunt for stations and multipliers.</p><p>Surprisingly it was the fixed direction high band yagis that caused the most confusion. It was very common for an operator to turn a rotatable yagi where it was wanted rather than click to select a fixed yagi pointed to the desired direction. I didn't anticipate that. From their feedback I learned that it was easy to "forget" about an antenna when there was no associated rotator. Similarly, splitting the stacks to maximum effect or using them to "spray" in different directions was a difficult concept to quickly master.</p><p>Antenna selection was easier on 40 meters since there are only two yagis. On 80 meters we usually kept to the vertical in preference to the inverted vee since we were primarily hunting DX. I say vertical rather than <a href="https://ve3vn.blogspot.com/2019/11/80-meter-vertical-yagi-completed.html">vertical yagi</a> because the yagi modes are only functional up to 3650 kHz. The array is optimized for CW. For most of the phone segment the array is only usable as a simple vertical. Yagi operation up to 3800 kHz has long been on my project list. Maybe next year.<br /></p><p></p><p>Mastering the Beverage receive antennas on 160 took practice. It was easy to understand but not necessarily easy to remember when and how to change direction. Since the Beverages can only be used by one radio at a time, despite having a <a href="https://ve3vn.blogspot.com/2020/05/beverage-remote-switch.html">choice of 6 directions</a>. I have begun construction of a second receive antenna and I hope to have it
ready by the end of the year. </p><p>For the contest I placed a manual antenna
switch on the operating desk to connect the Beverage system to one radio
or the other. I programmed the Icom 7610 to always use the receive antenna
port on 160 meters. On 80
meters it had to be manually selected in the Antennas menu. The FTdx5000 has a front panel switch.</p><p></p><p>The next big problem was the <u>amplifiers</u>. Mine are manual tune tube amps: an <a href="https://ve3vn.blogspot.com/2021/04/station-improvements-for-6-meters.html">Acom 1500</a> and a vintage <a href="https://ve3vn.blogspot.com/2019/04/going-qro.html">Drake L7</a>. At their own stations, the other operators either use no-tune solid state amps or do not currently have amps. They all know how to operate them, in general, but none had done so recently. That became a problem.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjkHyoj8XZOOW9sj8yL5R49-Ok9CtnE6vqB77ybl5IkCzUqTEhzPg1zQyOL7ZrRr7QXMBOmY2Gw-h2x4EdypaDMmpvFoY0h1W5a2QLel9DV30KSM080EmMIyYHYATgbrXiTPnLGOGjVZSAGa5Oo_uYnAGSiztM19w29E8gpdb5-iTNfjN-ZAW1k2pv57qol/s602/a1500_tuning_chart.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="602" data-original-width="600" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjkHyoj8XZOOW9sj8yL5R49-Ok9CtnE6vqB77ybl5IkCzUqTEhzPg1zQyOL7ZrRr7QXMBOmY2Gw-h2x4EdypaDMmpvFoY0h1W5a2QLel9DV30KSM080EmMIyYHYATgbrXiTPnLGOGjVZSAGa5Oo_uYnAGSiztM19w29E8gpdb5-iTNfjN-ZAW1k2pv57qol/w399-h400/a1500_tuning_chart.jpg" width="399" /></a></div><p style="text-align: left;">My attempt to be helpful wasn't as helpful as I'd hoped. Before the contest I made a tuning chart for the A1500 by tuning and documenting the Tune & Load settings across the SSB segments for every antenna. It got ridiculously complicated due to the many antennas.</p><p></p><p>Although precise tuning isn't necessary it does help to keep the amps running smoothly and it also maximizes tube life. Errors were made. No, <i>many </i>errors were made. When you haven't used an amp for a while it can be intimidating. It is also very inconvenient when changing antennas or clicking to work a multiplier 200 kHz away, and the tuning is very wrong. </p><p>Either the power output would be painfully low or the protection circuits would place the A1500 offline. Often the operator didn't notice until I pointed it out. Setting the drive level too low or too high was another common error. I jumped in to do a quick tune whenever necessary.<br /></p><p>Another confusion was the pair of foot switches for the FTdx5000: one for PTT and one to generate a carrier for tuning. Guess what happened more times than I care to think about!</p><p>The L7 is more forgiving since it uses 3-500Z triodes rather the tetrode in the Acom. For that reason I didn't bother with a tuning chart. However, it must still be tuned. Too often it wasn't and the power output was little better than running barefoot. Without a foot switch, the only way to generate a carrier was to use the CTRL-T function of N1MM+. </p><p>This is why many contest stations now use broadband solid state amps and broadband antennas such as OWA yagis and 4-squares. There are tube and solid state amps with built in ATUs, but those are expensive. One reason I like my amps is that they're cleaner than almost every solid state amp with regard to IMD and harmonics. I don't use BPF or stubs on the amps so that is important. We'll have to live with the hassle since I am unwilling to spend $20,000 for two new amplifiers with built in ATUs.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhoI8HPW37W8ElT1ukqrUhgP2TW6L91ws6mcnjj5csT66d57vj0BHtAKN3EPyRxldacqE_OyGA_ox9pChnL7Br3iAsD32kNYV2lTnXC754HFEB7X0clOn9RutoO9qqwjI03Hdx3h6yRTGdiem93QAjTQwk3IlH1rMNmvgm9lWr8wRA9kb1wNN8uFhJLFerw/s640/antenna_selector_ui_annotation.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="269" data-original-width="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhoI8HPW37W8ElT1ukqrUhgP2TW6L91ws6mcnjj5csT66d57vj0BHtAKN3EPyRxldacqE_OyGA_ox9pChnL7Br3iAsD32kNYV2lTnXC754HFEB7X0clOn9RutoO9qqwjI03Hdx3h6yRTGdiem93QAjTQwk3IlH1rMNmvgm9lWr8wRA9kb1wNN8uFhJLFerw/s16000/antenna_selector_ui_annotation.jpg" /></a></div><p style="text-align: left;">Which brings us to antenna control. For reading ease I've copied the original UI (user interface) from an <a href="https://ve3vn.blogspot.com/2022/07/station-automation-design-choices.html ">earlier article</a>. It's almost unchanged. You can read that article for detail on how it works. </p><p style="text-align: left;">Despite my misgivings, I didn't think it would fail as badly as it did. It was barely comprehensible to the others. I have a plan to make it much better, but I've had no time to work on it. </p><p></p><p>I was frequently guiding the operators on its use. Part of that was due to the poor design and part was their lack of familiarity with the antenna and rotation options (see above). The contest raised the redesign priority and I will get down to work this winter. In my defense, the first priority was getting the automation system working and the UI was rushed. It was never intended to be a final design.</p><p>The system itself glitched several times which it has never done before. It was always at night when we were active on the low bands, so it is likely due to RFI. Intermittent faults are difficult to track down so all I can do is add more RFI protection like toroids and bypass capacitors for every wire touching the Arduino controller and the cables to the PC. Transitioning from USB to Wi-Fi will help.</p><p>On the bright side, recovery was quick and easy. When it locks up the status bar turns yellow or red. The UI is shut down, the Arduino power cycled and the UI restarted. One time the PC required a restart to clear a COM port fault. It takes 30 seconds to restore service, or twice that when the PC must be restarted. SSD storage makes for very fast Windows restarts.</p><blockquote><pre><span style="font-size: small;"><i>Call: VE3VN
Operator(s): VE3KG VE3PJ VE3TM VE3VN
Station: VE3VN
Class: M/2 HP
QTH:
Operating Time (hrs): 48
<span style="font-family: courier_newregular,courier;">Summary:
Band QSOs Zones Countries
------------------------------
160: 116 10 14
80: 470 15 58
40: 1451 26 99
20: 1586 36 119
15: 1863 35 116
10: 1462 32 130
------------------------------
Total: 6948 154 536 Total Score = 12,442,770</span></i></span></pre></blockquote><p>With regard to operating strategy, I believe our greatest shortcoming was <u>multipliers</u>. The runs were so good and the operator enthusiasm so high that it was difficult to interrupt and suggest spending more time hunting multipliers. Not all of us were experienced or comfortable with clicking those spots or using the N1MM+ <a href="https://n1mmwp.hamdocs.com/manual-windows/available-mults-and-qs-window/">AMQ window</a>. </p><p>It takes practice and a sharp eye to click on a spot, call the station and resume running. Both radios have dual receive so it is possible to listen on two frequencies concurrently. I try do it when one or two CQs go unanswered. Timing is key. Multi-single teams have it easier since only one station can run; the other (or others) can only work multipliers on other bands. In M/2 we must carefully weigh the options.<br /></p><p>That is not to say our multiplier count was dreadful; we did pretty well (see above). Improvement will come with time. We could afford to lose a few multipliers since they were partly compensated by the high QSO points. I was more concerned with 80 and 160 meters since the runs were relatively weak and more time could have been spent hunting multipliers overnight. The rules allow us 8 band changes per hour, yet we never came close to the limit. I suspect that part of the problem was operator avoidance of frequent amplifier tuning (see above).<br /></p><p><b>The future</b></p><p>We'll do this again, with the same team or with others depending on availability and contest mode (SSB vs CW). I made a list of station improvements that I'll work on over the coming months. My objectives are to rise higher in the standings and increase operator enjoyment and engagement. I have an incentive to stick with a core team who will become familiar with the antennas, equipment and station features.<br /></p><p>I may gather a team for CQ WW CW at the end of November. If that occurs it will involve few if any improvements to the station. There have been other priorities in the waning weeks of fall while the weather is not yet very cold. The next likely opportunities are the ARRL DX contests early next year.</p><p>For the present, the operating desk has been reconfigured for SO2R, which I used for a casual effort in Sweepstakes CW. I will also need to spend time exchanging the IC7610 and FTdx5000MP so that the former becomes the primary operating rig for everyday operating.</p><p>Accommodating guests in my small house is a challenge. There is a guest
bedroom and an adjoining bathroom and shower, but that's it apart from
my own space and a couple of sofas. Old people tend to be finicky about these things but that
didn't seem to apply to this fine group of contesters. We made do with few
problems or complaints. That might not be the case with a larger team.
It is something to think about for future contests.</p><p><b>The past<br /></b></p><p>I am not a fan of nostalgia. Tube rigs and paper and pencil logging are history and they have no place in my shack. The fondness I feel about the past involves people. So bear with me as I finish this article with an old scanned photograph and a story.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-9t0TVHowQEkKPkijqyIPRVvVWiNqhhyQbQIUQqoHC9pMnx1vmBJbv1ercizZaBjzeZW8zP-UUgBhR_w3m6ovFF1TOCPmi7dWKoxUuVo8qDzSdsOuPuMDTx8BrzeH0LBv6u7Irhs1IU9jr_hkUB7CbVS0_tWx_YseTMsiHZ5X-dsgTomXh4Al4WqFvAgl/s800/ve3pca_circa1981.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="589" data-original-width="800" height="471" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-9t0TVHowQEkKPkijqyIPRVvVWiNqhhyQbQIUQqoHC9pMnx1vmBJbv1ercizZaBjzeZW8zP-UUgBhR_w3m6ovFF1TOCPmi7dWKoxUuVo8qDzSdsOuPuMDTx8BrzeH0LBv6u7Irhs1IU9jr_hkUB7CbVS0_tWx_YseTMsiHZ5X-dsgTomXh4Al4WqFvAgl/w640-h471/ve3pca_circa1981.jpg" width="640" /></a></div><p style="text-align: left;">The picture was likely taken in 1982, which is 41 years ago. It would have been at the end of one of the CQ WW or CQ WPX contests. Our multi-op call sign was VE3PCA. The station was owned by Doug VE3KKB (top centre) and located at his parents' rural home near the town of Perth. Those were good times. I was a lot younger then (left), new to VE3 and without a station of my own. I had yet to trim my 1970s hair. The others are Dave VE3KG (top right), Brian VE3CRG (lower right) and John ex-VE3EL (bottom, SK).</p><p></p><p>I have always enjoyed the energy level of multi-op contesting. I hate being alone in a room for 48 hours for single op contests and I hated it more when I was young. Joining a team at the moderately large station that Doug built was a great joy. Conditions were good, the camaraderie infectious and we sumptuously hosted by Doug's parents Mary and Jim (ex-VE3KJG). Both have long since passed.</p><p>By 1984 VE3PCA was no more. I had few opportunities to do a multi-op contest since. Later that year I bought a house and built my own modest station. In 1992 I exited the hobby entirely. When I <a href="https://ve3vn.blogspot.com/2013/02/no-longer-qrt.html">returned to amateur radio</a> 10 years ago, it wasn't long before I resumed contesting. First casually and then with enthusiasm. With my contesting interest rekindled I developed a long term plan to build a station that could do well in contests and host a multi-op. Mission accomplished. </p><p>The 4 surviving VE3PCA members in that picture remain friends. Brian VE3CRG continues to be very active on HF though not in contests. Doug VE3KKB has downsized his station and no longer has HF capability. Dave VE3KG, like me, continues to be very active. He was on our team for CQ WW SSB (see the pic near the beginning of the article). It is almost exactly 44 years since we did our first multi-op together. </p><p>Amateur radio, and contesting in particular, breeds long lasting friendships. We may not stay in frequent contact but when we do the good times return. My longest and firmest friendships are with fellow contesters. On the air you may hear <a href="http://ve3vn.blogspot.com/2023/05/hello-goodbye-in-praise-of-599-qsos.html">little more than "59 4"</a> but behind that brevity lies a rich culture, full of friends, pizza and smiles. Contesting, in my experience, is an extraordinarily social endeavour.</p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com0tag:blogger.com,1999:blog-6207999661586171874.post-75366415035941726102023-11-02T21:57:00.005-04:002023-11-02T22:01:16.785-04:00Rapid Tower Decommissioning<p>Hams with towers are growing old. Many young hams are content with simpler HF antennas that don't require a tower or a long term commitment. Lifestyles have changed over the decades. When a tower comes on the used market there is often little interest. Many are free for the taking, if you take them down. Few are willing.</p><p>What do you do when the ham passes away? Small towers can usually be taken down, and I've done that. They are then given away or sold by the estate. Home buyers prefer not to see a tower when shopping. Bigger towers are a greater challenge. The estate incurs the expense of professional removal, and that may be the only option. The cost can only be recovered if there's is a buyer once it is on the ground.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgys-XO1tLiMBIJ8imNcT9hlplD4OHboYPjY69J1xj_5Be4jU5hRnrmi_Ph0wy971d-TSGI7gdbtrF7UFIT-R3X3RcVAoiWqjIvZPGZk0W7ILEx78lLQ0GW2T7TF3vSvm9ca4ctDGZesOvlqpVxyRphFayavV8P6ZSaqwxVHfdV8PRFTmxVSg39G6k2q0wB/s492/zq_tower.JPG" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="492" data-original-width="179" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgys-XO1tLiMBIJ8imNcT9hlplD4OHboYPjY69J1xj_5Be4jU5hRnrmi_Ph0wy971d-TSGI7gdbtrF7UFIT-R3X3RcVAoiWqjIvZPGZk0W7ILEx78lLQ0GW2T7TF3vSvm9ca4ctDGZesOvlqpVxyRphFayavV8P6ZSaqwxVHfdV8PRFTmxVSg39G6k2q0wB/s16000/zq_tower.JPG" /></a></div><p style="text-align: left;">A friend (Dave VE3KG) has been helping the widow of a silent key (Ajmal Rahman ex-VA3ZQ, and formerly VE2ZQ and AP2ZQ) to dispose of his station. He had a dilemma: a 110' guyed tower that no one wanted. Without a buyer, it wasn't worth the trouble and expense to dismantle it. Due to the illness of the owner preceding his death, it was in a state of disrepair. </p><p></p><p>I previously <a href="https://ve3vn.blogspot.com/2023/09/singing-isnt-just-about-element.html">showed</a> a picture of the tower on this blog, along with the antenna parts that had broken and fallen to the ground. At right is a full height picture taken this past summer.<br /></p><p>I knew Ajmal a long time ago. When I dropped out of the hobby I did not stay in touch with many ham friends. The last time we spoke was at least 30 years ago. I visited his country home when his family was young and he was eager to build an effective HF station. The tower was raised soon after.<br /></p><p>Following my inspection, I decided that the tower was safe to climb despite several issues. But to what purpose? There was little of value to salvage. A lightning strike several years previous had disabled the rotator and likely destroyed some or all of the cables. With fatigued elements having fallen to the ground, the antennas were little better than scrap. The house was being sold and the tower had to go. We decided it would have to be cut down.</p><p>That is easier said than done. There are many things that can go wrong in that seemingly simple operation. Risk of injuries to people and property should not burden the family. Despite the large size of the property there were several complications due to the property layout and guying. </p><p>We considered options while waiting for a neighbour to drive over with his bush hog to clear the field around the tower. There was lots of time on our hands since he didn't show up until two months later. Luckily the house hadn't been sold in the interim.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEirh7t4Tur7PvheBCfSpqcpQFvouLdRXRIEzixy1ciSAp35oLrrTQG8sijONxY5NoTMC5fgvZwViCg-j4IGBoejcMnSi6aN1UPDktAw47xnEhrCc7vTbQlYTRsrv0Xb1VfR3me4X17AF0fV1Ez9d-9Of__Fx3CJyaOqS9F8rb0rRCPCgZX1bdLdYBJRLff4/s616/zq_site_plan.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="616" data-original-width="595" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEirh7t4Tur7PvheBCfSpqcpQFvouLdRXRIEzixy1ciSAp35oLrrTQG8sijONxY5NoTMC5fgvZwViCg-j4IGBoejcMnSi6aN1UPDktAw47xnEhrCc7vTbQlYTRsrv0Xb1VfR3me4X17AF0fV1Ez9d-9Of__Fx3CJyaOqS9F8rb0rRCPCgZX1bdLdYBJRLff4/s16000/zq_site_plan.jpg" /></a></div><p style="text-align: left;">The tower and property are annotated on this Google satellite view. The yellow dots are the approximate location of the guy anchors, the orange letters are hazards and the red arrows are the directions the tower is most likely to fall when the opposite anchor is severed. The gray circle is the approximate 120' fall radius (tower height plus mast and yagi measured on the ground from the pier pin base).</p><p></p><p>There are a few general concerns about felling a tower in this manner:</p><ol style="text-align: left;"><li>The fall radius is the <i>minimum </i>distance where debris will land. Tall towers can bounce. Their forward momentum can take them beyond the marked circle. Although that isn't likely for a tower of this size it must be taken into account.</li><li>Debris from the tower top can be dispersed well beyond the fall radius. Impact velocity and momentum are very high. Mast, antennas and other attachments can break off and take flight to damage property and injure unprotected people in the vicinity. Spectators must keep their distance.<br /></li><li>Towers are <i>most </i>likely to fall in the direction opposite of the cut guy anchor. However they can fall in any direction in which the remaining guys are slack. That covers a lot of ground. Steps must be taken to ensure the tower falls where you want unless there are no hazards in the path of the tower or the two intact sets of guys.<br /></li></ol><p>We are now in a position to discuss the three fall directions and their hazards. </p><p>The <u>south anchor</u> is inside the edge of the bush. Only a little vegetation had to be fought to access it. By dropping the tower to the north it would likely fall across the eastern edge of the lawn. That's undesirable but in this case was permitted. </p><p>The problem is the northwest anchor and hazard C. I won't draw a diagram so you'll have to visualize the scenario. C is a mature hardwood about 30' to 40' tall. When the tower topples forward the guys attached to the northwest anchor would wrap around the tree. That would severely injure or kill the tree. Worse, the tangling would cause the tower to veer left into the lawn and towards hazard E, the house. </p><p>The first is very unwelcome and the second is unacceptable due to the risk of flying debris and lawn damage. I've seen the effects of a yagi striking a house when a 120' tower unexpectedly collapsed. It wasn't pretty.<br /></p><p>The <u>northwest anchor</u> we just discussed has bushes growing all around but they were easily removed to reach the anchor. By cutting that anchor the tower would fall to the southeast. No matter how it falls there would be no risk of damage to anything of value. That sounds wonderful but for two things.</p><p>First, a tower falling into a forest typically will not reach the ground. A tower hanging overhead amid a tangle of broken tree limbs is not easily or safely removed. Neither is it easy to reach since the bush in front of the trees is dense and more than head height. I tried to get in there for a look and quickly decided it wasn't worth the trouble, both for the aforementioned problem and because of hazard D. That's the property line. We were told that it wasn't acceptable to fell the tower into the neighbour's patch of forest.</p><p>The <u>northeast anchor</u> was easily accessed once the bush hog levelled the field. The open field seemed an ideal landing area and the guys from the other anchors would easily cut through the light bushes on their west sides. Which brings us to hazards A and B.</p><p>Hazard A is utility pole supporting a transformer and hazard B is the distribution line and includes the telephone service cable. The fall radius comes almost exactly to the pole's guy anchor that stretches a short distance to the east (barely visible in the satellite photo). The distribution line at southwest corner of the property is 200' from the tower and well outside the fall radius. Potential debris set flying from the impact is at risk of hitting the anchor, pole or distribution line.</p><p>The red X marks the desired fall target. <br /></p><p><b>"A ham's got to know his limitations"</b></p><p>It was at that point I recommended calling in the professionals. I was not comfortable taking on the job using a crew of hams who understood even less about the procedure than I did. I received good advice and an offer of tools from someone of my acquaintance in the commercial business in case I decided to take it on. </p><p>He agreed with me that the best option was to cut the northeast anchor. When the anchor was cut, a rope tied to near the top of the tower has to be pulled hard within 2 seconds of separation to direct the tower to fall where we wanted. That's a precision operation. I considered the options and the procedure details and I decided it was outside of my comfort zone. Although I believed the chance of success would be very high, the cost of failure, low risk that it was, was too high to bear.</p><p>The firm I called on, <a href="https://ontower.ca/">Ontower</a>, is very familiar to me and they are located a 30 minute drive from the site. The owner stopped by the site and agreed with the level of risk. A simple "cut and run" felling was out of the question. The recommended options were a crane to lay it down or bring a full crew to manage a precision fall to the target in the southwest area of the property. Cranes are expensive so we got the widow's approval to do the latter. Since the firm is fully insured, the risk of failure was covered.</p><p><b>Felling a tower</b> <br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEilt_HZerJVSufzO3Do18sz1TYw9wqsxu1GszqB3mL3-YP5uhVkdRup_8cbWwaKAwdINbNdY7fJrdrAfkhzCR0P_H6mWiiYqNE4SHUlEjv4NGOM57TOTvBRVAl9vmCsAJ84dJ9LiiJR84Wd-2HVu8bnFNNqaVoWndOdOtR-4q0wszLzpD8Ag_ggkAvK7Xz_/s600/zq_cut_anchor.JPG" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="441" data-original-width="600" height="294" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEilt_HZerJVSufzO3Do18sz1TYw9wqsxu1GszqB3mL3-YP5uhVkdRup_8cbWwaKAwdINbNdY7fJrdrAfkhzCR0P_H6mWiiYqNE4SHUlEjv4NGOM57TOTvBRVAl9vmCsAJ84dJ9LiiJR84Wd-2HVu8bnFNNqaVoWndOdOtR-4q0wszLzpD8Ag_ggkAvK7Xz_/w400-h294/zq_cut_anchor.JPG" width="400" /></a></div><p style="text-align: left;">The appointed day was the Tuesday morning following the CQ WW SSB contest. It was a hectic weekend in which our team of 4 did pretty well. I'll have more to say about the contest in a future article. </p><p></p><p>One of the multi-op team members, Dave VE3KG, was there with me. He knew Ajmal far better than I did and took the lead helping his widow dispose of the station. All the pictures and video in this article were taken by him. I was going to do it but after the first picture my phone battery went dead. I forgot to charge it.</p><p>The first job was to expose the guy anchors. All were galvanized angle stock, with two being ⅜" and the northeast anchor was about 3/16". One extended above grade, one was at grade and one was below grade. Use of angles is unconventional but perfectly fine if <a href="https://ve3vn.blogspot.com/2018/12/customizing-guy-hardware.html">sized appropriately</a>. What was very unusual was the use of shackles to tie the turnbuckles directly to the angle, spread onto the two faces of the steel. That's awkward. A header is preferred.</p><p>The picture gives you an idea of the anchor style since I don't have a picture of the northeast anchor that was cut. They dug deeper than I did during my inspection to expose over a foot of it. The gas powered cut off saw needed space to work. The <a href="https://ve3vn.blogspot.com/2018/06/tuning-up-tower-guys.html">safeties</a> had to be cut since, for reasons unknown, they appeared to be tied into the (presumably) concrete anchor further down. </p><p>All guys are often loosened before cutting the anchor. In this case they decided against it, using the tension of the other guys to start it falling in the approximately correct direction. The cut anchor and its guys recoil violently towards the tower when it is done this way. </p><p></p><table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6uwYGGisRV5-gAYnxy8bTdNBxGPp_KrdyQ2oi36hTdcZGQiM4wf9syVc4MHc89dhhvh0u5ZAXZK8fu25VomFk7c7wghxCobsmcTskUR95ewcYnET-ZWiIU36AhhIJvwn2kB2umQ1M7xjP-DMt44TgQSdB_Ac2-8XiOiAnTnpww4IxNQ9P9sGOZeNYsylE/s187/zq_video_frame.png" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="187" data-original-width="156" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6uwYGGisRV5-gAYnxy8bTdNBxGPp_KrdyQ2oi36hTdcZGQiM4wf9syVc4MHc89dhhvh0u5ZAXZK8fu25VomFk7c7wghxCobsmcTskUR95ewcYnET-ZWiIU36AhhIJvwn2kB2umQ1M7xjP-DMt44TgQSdB_Ac2-8XiOiAnTnpww4IxNQ9P9sGOZeNYsylE/w167-h200/zq_video_frame.png" width="167" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;"><a href="https://youtube.com/shorts/iT4CtAq84zE?feature=share">Click to view on YouTube</a><br /></td></tr></tbody></table><p style="text-align: left;">A rigger tied a rope about 80' up the tower. The other end extended to the southwest corner of the property. One of the two most experienced crew cut through the northeast anchor while the other maintained tension on the rope. The fall happens very quickly. </p><p style="text-align: left;">Once the tower starts moving, the forward momentum becomes too high to direct the tower. There would have been less than 2 seconds to pull the tower while it was near vertical. That's why the person on the rope maintained tension throughout the cutting -- there was no time to communicate over the almost 100 meter distance at the moment the anchor was severed. The person on the rope can feel when the cut guys go slack and do what's necessary.<br /></p><p></p><p>I'm sure many of you are expecting a video. We have one! Dave pulled out his phone and recorded the cutting and the fall. It's short and 95% of it is the cutting. The tower falls fast. We were of course told to stand well back. The falling tower hit the bullseye. It was a neat job. Professionals make it look easy. It isn't.<br /></p><p><b>Salvage</b></p><p>With the tower on ground, our thoughts turned to salvage. The disposition of everything was not yet decided as I write this article. The crew separated all the sections while we inspected and disconnected the rotator and mast. The foreman brought the saw over to speed the work by cutting both steel and aluminum jammed into the ground. </p><p>He then inspected every tower section and cut through one leg of the sections that were damaged. This is a smart way to discourage hams from the temptation to reuse them. An hour later they were done. They were on site for little more than 2 hours. </p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrLJvE1GRiFi568JxE0lMCFfY5wm_dr1hU538x3PPf5mmalkA9fiRK9ON6Im0weiP2wev7-Md3QGhpSh-Qrbkl8yLgGPmKOI5ZmxMSYhttYccTlBJ5OHBfziayIfRUaLYtQ8oLvURV1tHanZAgo5OrqZ_DGzZ3dtzpI9phx9VSK6nKcTPd31xALaSmckuH/s666/zq_tower_sections.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="666" data-original-width="600" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrLJvE1GRiFi568JxE0lMCFfY5wm_dr1hU538x3PPf5mmalkA9fiRK9ON6Im0weiP2wev7-Md3QGhpSh-Qrbkl8yLgGPmKOI5ZmxMSYhttYccTlBJ5OHBfziayIfRUaLYtQ8oLvURV1tHanZAgo5OrqZ_DGzZ3dtzpI9phx9VSK6nKcTPd31xALaSmckuH/w576-h640/zq_tower_sections.JPG" width="576" /></a></div><p style="text-align: left;">There are aluminum bars that can be reused, but the the guys are scrap other than, perhaps, the porcelain insulators. The short fibreglass rods that electrically decouple the tower from the EHS guys are old, likely damaged from the fall and partially delaminated. While tempting, they must not be reused.</p><p></p><p>The only prize I left with was a Tailtwister rotator. Although damaged by the fall it might be reparable. I can use it for parts if not. I'll open it up for inspection later this fall and if it looks interesting I'll write it up for the blog.</p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com2tag:blogger.com,1999:blog-6207999661586171874.post-41719919706198127882023-10-26T23:01:00.001-04:002023-10-26T23:01:52.088-04:00New Rig: Icom 7610<p>For several years I've had a new transceiver in my annual plan. This year was no different. What is different this year is that I finally did it. The spur was the upcoming CQ WW SSB contest. Since this will be the first multi-op contest from my station, I was uncomfortable asking others to put up with the relatively ancient Yaesu FT950. It was only marginally acceptable when it was just me using it, and then only during contests when I operated SO2R.</p><p>The FT950 is not that bad of a rig, for its time. It is unsuitable for a modern contest station where I want ultimate performance. I've had it for years and it did what I asked of it, and it is now set aside. For the time being it will be a backup rig. It will eventually be sold. Due to the march of technology, perfectly good rigs of an earlier generation fetch <a href="https://ve3vn.blogspot.com/2020/08/price-vs-value-economics-of-used.html">increasingly lower resale prices</a>. It is almost not worth selling.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj96bjsq35R1Y-dB4lg4HhfqrCcBibL5tFNwOzZW01P3cyc__A5X-vRqktjXzQc-sQSCJKWTvRRKjAISWzsae9v_e375k4PImfZgXgH-hLHvbveoOxWaohcP-uBGMuxmnp46CAcSM7trH193CLhZIy9jJuWHdLRANGpk2H3-XQzHs8B4mRng-RZIdkk163q/s800/ic7610_installed.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="458" data-original-width="800" height="366" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj96bjsq35R1Y-dB4lg4HhfqrCcBibL5tFNwOzZW01P3cyc__A5X-vRqktjXzQc-sQSCJKWTvRRKjAISWzsae9v_e375k4PImfZgXgH-hLHvbveoOxWaohcP-uBGMuxmnp46CAcSM7trH193CLhZIy9jJuWHdLRANGpk2H3-XQzHs8B4mRng-RZIdkk163q/w640-h366/ic7610_installed.jpg" width="640" /></a></div><p style="text-align: left;">The IC7610 is a complex rig and there is much to learn. I have to learn quickly because the contest is almost here. I moved slowly while setting it up and integrating it into the station to avoid mistakes. For now it is a drop in substite for the second operating position. When the contest is behind me it will be become the rig for the main station. The Yaesu FTdx5000MP will be demoted to the second operating position. It has been my primary rig for <a href="https://ve3vn.blogspot.com/2017/02/new-rig-in-new-shack.html">more than 6 years</a>, but it's time for it to be set aside.<br /></p><p></p><p>As I said, it's an expensive item and I did not spend the money without due consideration. Is it worth the money? Many hams would never spend that much on a transceiver; I know that I am reluctant to do so. Needs and means are different for each of us, and for me this was the right choice.<br /></p><p>Here's how it looks in the shack, as it has been rearranged for two-position multi-op in CQ WW.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigKxGB6NbleVg0QDKG_9NKnjdZXx2EMiV-0yizOQarOVbLwrzXu-iGbaYJawfbugGwFSy3cRU5TOOmnh3sT2dzo0lVpIcgaMNil12o0zHFv7oVkmdPMI_YkZ1gRdxBwUUg3f-xuvs8BgeCg9d28AAxKu47tldGVM61C8mGOK3kcndlMn08-I_UE-t2YDoz/s800/cqwwssb_setup.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="489" data-original-width="800" height="392" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigKxGB6NbleVg0QDKG_9NKnjdZXx2EMiV-0yizOQarOVbLwrzXu-iGbaYJawfbugGwFSy3cRU5TOOmnh3sT2dzo0lVpIcgaMNil12o0zHFv7oVkmdPMI_YkZ1gRdxBwUUg3f-xuvs8BgeCg9d28AAxKu47tldGVM61C8mGOK3kcndlMn08-I_UE-t2YDoz/w640-h392/cqwwssb_setup.jpg" width="640" /></a></div><p style="text-align: left;">It's small and light, and hardly looks as if it is worth the price. The FTdx5000MP is nearly 3× its weight. When the contest is behind me, I will get deeper into its features and capability. For the next few days I am solely focussed on the features needed during the contest. I am likely to have more to say about the 7610 in the future.</p><p></p><p>The following is a quick take based on my first impressions. Bear in mind that first impressions can be wrong. Do not interpret this article as a review because it isn't.<br /></p><p><b>Buttons</b></p><p>The FTdx5000 has almost every operator feature on the front panel. The panel is large, the buttons many, and the buttons are small. It has to be this way because the features are many and the text-based menu system is slow and difficult to navigate. This high end rig predates the adoption of touch screens. It is one of the last of the "big iron" transceivers. </p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiRAAjRMjIZSKDP773RnZ2lYpAgacBu4j92PSr1DTOTRk5lPHwPwjX4kcnj4qZpMsqnVyJGbRA6cx-WwV3ye_1riyrS0ZBBhZyP8AcSqp4pj23i-IqnAfX8FvTb2MCLHWfiD7O7tjmb2jOfrdAZvOQvKU3lObES-XSrWoGmiIDLnb2i_9KsWbpSTw14whjK/s1200/ftdx5000mp_front_panel.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="376" data-original-width="1200" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiRAAjRMjIZSKDP773RnZ2lYpAgacBu4j92PSr1DTOTRk5lPHwPwjX4kcnj4qZpMsqnVyJGbRA6cx-WwV3ye_1riyrS0ZBBhZyP8AcSqp4pj23i-IqnAfX8FvTb2MCLHWfiD7O7tjmb2jOfrdAZvOQvKU3lObES-XSrWoGmiIDLnb2i_9KsWbpSTw14whjK/w640-h200/ftdx5000mp_front_panel.jpg" width="640" /></a></div><p style="text-align: left;">Buttons have their good and bad points. The majority of the features are not used or rarely used. That's a waste of panel real estate. They are small and hard to read, especially in dim lighting. You remember the buttons you regularly use and mostly ignore the others. Another point that is rarely considered is that cleaning the multitude of tiny buttons and knobs with their textured rubbery surfaces is difficult. But it must be done. A years long buildup of dirt, grime and skin oil is a subject best avoided in polite company.<br /></p><p style="text-align: left;">The OLED displays age poorly and, as you can see, the ones on the lower right are in dire need of replacement. This is a well known flaw of the '5000. Their replacement will be a winter project. </p><p style="text-align: left;">Another problem with many closely space buttons and knobs is that it's easy to grab the wrong one while you're operating. Often you will accidentally bump the ones nearby with unpredictable results. If it's a feature you rarely use it can take some time to figure out what happened and to correct it.</p><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjVQgQpHjfe8bsOIaZYcOPJxPPOQUOEuYqDxDJBDTBFzslthwTaePqR_Gg74Yn5LhRx94jzekZUys6fNT3xfNlXADTMTYCu1G0emo-Y0UbHY68iLlL2GnFFaPzyyaImXH3gG90akM1AAm8Lv_cTveGvJIvFDcrKSu0UwOUrbibkDR3kmwDzmc-YIDJfQ3ef/s800/ic7610_main_menu.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="452" data-original-width="800" height="362" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjVQgQpHjfe8bsOIaZYcOPJxPPOQUOEuYqDxDJBDTBFzslthwTaePqR_Gg74Yn5LhRx94jzekZUys6fNT3xfNlXADTMTYCu1G0emo-Y0UbHY68iLlL2GnFFaPzyyaImXH3gG90akM1AAm8Lv_cTveGvJIvFDcrKSu0UwOUrbibkDR3kmwDzmc-YIDJfQ3ef/w640-h362/ic7610_main_menu.jpg" width="640" /></a></div><br />There are few buttons on the IC7610 front panel. A large fraction of the space is taken by a touchscreen where many features can be directly accessed or accessed via the menus. Whether the physical buttons are assigned to the right features is debatable. Operators will have different opinions depending on their individual needs and interests. It's too soon to have developed a solid opinion of my own.<br /><p></p><p></p><p><b>Menu maze</b></p><p>The number of transceiver features increases with every generation of technology. Buttons and knobs for all of them is impractical. Of course there are many rigs that are designed to have a small feature set and don't need more than a few buttons and knobs. But those are usually smaller or special purpose products that take a minimalist approach for specific purposes such as portable operation. High end rigs are feature rich and need menus.</p><p>Although they many be necessary, menus are not always better than buttons. For a sophisticated rig like the IC7610 the menu system is a deep tree with many branches. It can be difficult to reach many features or even to know where to look in the menu system. </p><p>The names of novel features can be so unfamiliar that you can easily pass by the one you want. Reading manuals is tedious, and there are two of them for the IC7610, the basic and the advanced. Both are large and from my reading the descriptions are occasionally puzzling or incomplete.</p><p>That said, the menu system for the IC7610 isn't that bad considering its extensive feature set. Pressing the Multi key (upper right) displays a context sensitive list of only a few features. For example, transmitter power and mic gain. There are several context sensitive features on the left side of the touchscreen that can be directly accessed by a short or long press.</p><p>It took me several days to become reasonably comfortable with the menu system. Every modern rig has a learning curve and each manufacturer has their own ideas for menu design. There are many critics of the FTdx101's menu system. I tried it for myself in Dayton last year. That is one reason I favoured Icom for this purchase.</p><p>Menus are a necessary modern evil, so I live with it. I escape a lot of the tedium of operating feature use, like with RIT and XIT, using the <a href="https://n1mmwp.hamdocs.com/setup/keyboard-shortcuts/">keyboard commands of N1MM+</a>. I preferentially do that whether or not I'm in a contest. There's less to learn because the N1MM+ keyboard shortcuts for common features are the same for most every rig.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh78aPhFkhYEfgYTrvwT9MT-pINPVAXY6VSbGYGi6rC97QzSEZG6LVmMVFIJyy8kT-Ua3h8h-gfbTK8R4g25eEWetgGgy-7hSibfhUAOEcvXWdsGL0pzRiB-UttI2eqoHVkfDgt8kh_X6S54f7sDMBkc9NVpjDgjtgZJICAZSAPYm3HooX-oiykrk7pDKcY/s518/ic7610_electret_adaptor.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="518" data-original-width="400" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh78aPhFkhYEfgYTrvwT9MT-pINPVAXY6VSbGYGi6rC97QzSEZG6LVmMVFIJyy8kT-Ua3h8h-gfbTK8R4g25eEWetgGgy-7hSibfhUAOEcvXWdsGL0pzRiB-UttI2eqoHVkfDgt8kh_X6S54f7sDMBkc9NVpjDgjtgZJICAZSAPYm3HooX-oiykrk7pDKcY/s320/ic7610_electret_adaptor.jpg" width="247" /></a></div><p style="text-align: left;"><b>Connector standards</b></p><p></p><p>The simplest things can cause a lot of grief. The most basic interconnection needs are the microphone, headphones, keyer and PTT (in and out). At least headphone and keyer jacks are almost always ¼" or 3.5 mm. I'd prefer they all were 3.5 mm but I can deal with it using the adaptors I've accumulated over the years.</p><p>But...microphones? Dynamic vs. electret, 3.5 mm vs 8-pin Foster, and different pin outs for the same physical connector. This must be quite the revenue generator going by the extortionate prices they charge for their branded lines of microphones, complete with their unique mic connectors and features. One of my first jobs was to make an adaptor for the 8-pin Foster connector to allow connection of a 3.5 mm electret mic almost universally used for PC headsets. A USB headset connector would be even better. The connectors are right there on the 7610 just above the mic connector.</p><p>PTT was easier in one respect. Unlike so many transceivers, the PTT line (that they call Send for some reason or other -- see my thoughts further below) is a simple phono connector. I have loads of phono-to-phono cables. However, there is nothing simple about connecting a foot switch and keyer for PTT control (that they confusingly also call Send). There's an 8-pin DIN (ACC1) where that resides. </p><p></p><p style="text-align: left;">The rig does not include the DIN connector. In fact, the only connector they include with a multi-thousand dollar piece of equipment is a ¼" stereo plug. Typical of most transceivers, the interconnecting cables are included with the other equipment that they sell. In most cases it's their amplifiers.</p><p></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg1dNgS30ku6EJlJcUSKtRlkDlqWDnIGnj6Ve4qrc5GBK33d8rfT2fklT3dTmmPZSw0pvKjb9rJmzILOjbbIkGRk7vMAw-LDCuuxUN9WV9pHAedziC5UI3M1p4Wsp-cX75-tda-_bA6UhveD2EbMmK3M6WOKzrL8OaLkwa9TOJPRI0QIAr6n8sBIu5iSHkE/s555/ic7610_ptt_in_adaptor.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="555" data-original-width="400" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg1dNgS30ku6EJlJcUSKtRlkDlqWDnIGnj6Ve4qrc5GBK33d8rfT2fklT3dTmmPZSw0pvKjb9rJmzILOjbbIkGRk7vMAw-LDCuuxUN9WV9pHAedziC5UI3M1p4Wsp-cX75-tda-_bA6UhveD2EbMmK3M6WOKzrL8OaLkwa9TOJPRI0QIAr6n8sBIu5iSHkE/s320/ic7610_ptt_in_adaptor.jpg" width="231" /></a></div>By some miracle I found one of these connectors lying at the bottom of a box full of orphan connectors and cables that I've accumulated over the decades. I soldered on a phone jack and plugged a splitter into that. I could finally connect the foot switch and keyer.<br /><p></p><p><b>USB</b></p><p>The USB connection to the PC removes clutter from the back of the rig. One cable replaces several. Since it provides both CAT and a sound card, there are no separate audio cables. </p><p>There is a prescribed installation process to properly install the driver so that Windows doesn't substitute its preferred driver with which the interface will not work. I appear to have done it correctly since everything works as it should.</p><p>One way in which Icom is deficient in comparison to other manufacturers is that not every function on the rig is accessible or completely controllable by the PC. I knew this in advance. There are a few peculiarities when using N1MM+ despite the development team's best effort to overcome those deficiencies. I can live with it.</p><p>One day soon I hope we can eliminate the cables entirely when the PC connection evolves to wireless and TCP/IP. Some rigs have already done so and I expect the rest to eventually follow. But for now this style of PC interface is good enough.<br /></p><p><b>It's different</b></p><p>Equipment manufacturers have most of the same features as all the others in the same price class. Of course they also have unique features, and those can be very useful. Competition is good! What annoys me is that for the common features they too often use unique terminology and methods to manipulate those features. This has proved to be an obstacle since I've never owned an Icom HF rig before. I had to figure out their names for the features that I am familiar with.</p><p>For example, what most hams call RIT and XIT is called the Clarifier by Yaesu. Icom uses the more common terms so this was easy and welcome. The Twin PBT feature of the 7610 is very nice, but only once I figured out the relationship between the high/low cutoffs, filter selection and width controls and their relationship to the CW pitch control. Okay, maybe that isn't too difficult a difference.</p><p>There is a prominent button above the VFO knob labelled Change. Change what? So I pressed it and discovered it's what most other rigs call the A⟺B feature to swap the contents of the two VFOs. I'm still trying to figure out what the XFC button symbolizes but I did finally figure out what it's used for. The bizarre name does not make it intuitive. I'm still puzzling out split and dual watch which we need for 40 meters in the contest.<br /></p><p>I was surprised to find that the AF Gain also controls the volume of the CW side tone monitor. That's very odd. It was disconcerting when I first encountered it when, after turning down the gain, I had difficulty hearing what I was sending when I next transmitted. </p><p>Speaking of CW, why can't there be a common usage for normal and reverse CW reception? CW (normal) on this rig is the opposite of what I expect (USB reception), and was pretty well the standard decades ago when tubes ruled the airwaves. At least I could reverse the default behavior of CW and CW-R deep within the menu maze.</p><p>One thing I really liked was the speed of the ATU. Compared to previous rigs I've owned or used it's wonderful. Not only that, the tuner setting hold over 100 kHz. This is far better than the 10 kHz typical of so many other rigs. Unless you use a small magnetic loop antenna there is no need to tune every few kilohertz.<br /></p><p>Well, there's lots more I won't bore readers with. You get the idea. Like connectors, I wish rig manufacturers would standardize more of their terminology for common features. They have no particular incentive to do so since their customers don't base their purchasing decisions on it.</p><p><b>Contest priority<br /></b></p><p>I am trying to understand this rig in time for CQ WW SSB this weekend. When the team arrives I have to be able to explain to them how the rig works. I'm getting closer so we'll have to see how it goes.</p><p>After the contest I'll have a better understanding. Expect to hear more about the rig and other contest matters after the weekend is in the rear view mirror. When there's a long enough break between contests and DXpeditions I'll swap the IC7610 and FTdx5000MP to make the former my main rig.</p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com0tag:blogger.com,1999:blog-6207999661586171874.post-73615442221773400392023-10-17T22:43:00.003-04:002023-10-20T17:11:48.449-04:00Belated 6 Meter Season Report<p>Each year I report on my 6 meter experiences after the end of the sporadic E season. It usually comes out in mid-August. This year I'm 2 months late; it is not because I've been putting it off. The season was not the greatest and with the increasing solar flux and the approach of the fall equinox I hoped that I would have more of interest to say by waiting. </p><p>I regret to say that I was disappointed with both sporadic E and equinox north-south propagation (TEP). That makes the year interesting in some respects and less so with regard to my (and others') achievements this year. </p><p>Despite the disappointments, let's go ahead and recap the year. We can learn from mediocre results, often more than with spectacular results. Many may therefore find this article uninteresting. Since I find it educational, I'll press on regardless. Read on if you will.<br /></p><p><b>Perspectives on propagation</b><br /></p><p>Reports of the sporadic E season have varied. In this part of the world the experience seems to have been mostly poor. Others had greater success. Propagation is not the same for everyone. If you're an ARRL member, please read the VHF column in the October QST which contrasted the differences among locations. A lucky few had great propagation this year.<br /></p><p>Antennas matter. The more marginal the propagation the more the antennas matter. It is common for those stations to have openings that others nearby do not. I frequently notice this since my 6 meter antenna is higher and bigger than many of my friends. There are many bigger stations and in better locations who do far better than I ever will.<br /></p><p>TEP to the southern hemisphere has been productive though not as good as I had hoped. The fall equinox season had one good opening and many "teasers" in which little could be worked. However the spring equinox season was good. It delivered numerous openings to South America which netted two new countries (more on that below).</p><p>Europe, the usual stalwart, delivered only a handful of good openings during the sporadic E season. When it was in it was pretty good, covering every corner of the continent. There is a lot of activity in Europe so that when there is a path we know it on this side of the Atlantic. Unfortunately I failed to work any new European countries. That said, there are only a few European countries that I have yet to work!<br /></p><p>F2 paths that rely on a sustained high solar flux have been absent in 2023. Our geomagnetic latitude is higher than the geographic latitude due to the position of the <a href="https://en.wikipedia.org/wiki/Geomagnetic_pole">geomagnetic pole</a>. The average flux is rising at a steady and slow pace so there is hope for better next year. I say next year because as daylight fades with the approach of winter so do our prospects for F2 openings over the next several months.<br /></p><p>Perhaps my disappointment is due to having experienced several good years of sporadic E propagation. Although 2023 has been poor, it was not worse than the worst I've seen since I returned to 6 meters in 2017. Propagation has its ups and downs, sporadic E is sporadic and sunspots come and go. 6 meters is the magic band and magic is fickle. The long anticipation of yet-to-arrived DX openings requiring a sustained solar flux of 200 tries our patience.<br /></p><p>As I often say, if it was easy what would be the point? A challenge is what motivates station and skills improvement. It's us against nature and the laws of physics. Technical advances have made predicting and finding DX openings easier, but technology cannot manufacture openings. We learn, improve and measure our progress by our successes and our failures.</p><p>There was one very good aurora session this year. That netted contacts stretching across the northern US as far as Idaho. Although not DX, it was exciting to do well on aurora. That's one of the rare times I shut down WSJT-X and put the paddles to work. FTx modes are not compatible with aurora Doppler. We can expect more aurora propagation as the solar cycle peaks and then slides down the other side.<br /></p><p>My log tells me that I made about 350 contacts on 6 meters this year. Most was via sporadic E. The total could have been much higher but I am not very interested in non-DX. I monitor most openings, scan the DX spotting networks and I will occasionally CQ into a seemingly dead band. Catching those brief and weak DX openings takes effort. Many times I am out of the shack when the band opens and I miss out.<br /></p><p><b>New countries</b></p><p>My count of DXCC countries increased from 120 to 131. That's worked, not confirmed. On LoTW (the only way I confirm contacts) I have 120 confirmed. While I do operate CW and SSB when conditions warrant, all of my new countries are on FT8.<br /></p><p>11 countries isn't much. A higher annual increment is unlikely until the solar flux increases enough to sustain F2 openings at this high geomagnetic latitude. As I said at the <a href="https://ve3vn.blogspot.com/2022/08/6-meter-season-diminishing-returns.html">end of the 2022 season</a>, I've reached the point on diminishing returns: each new one takes more effort than those that came before.</p><p>The most noteworthy new country I worked this year was New Zealand. I've heard ZL before but previous openings were too fleeting to make a QSO. Back in June, <a href="https://ve3vn.blogspot.com/2023/06/new-zealand-on-6-meters.html">ZL1RS</a> was not only workable, I was able to copy him pretty well for more than 20 minutes. I briefly heard but could not work two other ZL stations that evening. </p><p>The other new one in the <a href="https://ve3vn.blogspot.com/2023/03/whet-appetite-6-meters.html">Pacific direction</a> was FK8. They were in fairly consistently for several days in the spring. Then they were gone and they haven't been heard since. The solar flux hasn't risen too high for several months. On one of the days FK8 was heard, several strong Hawaii stations were rolling in but none that I haven't work before.<br /></p><p>Another interesting new country was Angola. D2UY has been heard here and elsewhere in eastern NA quite regularly early in the year. On one day, and one day only, his signal was in for long enough to allow a QSO. There is not a lot of activity in Africa so every new country from there is an accomplishment. I heard and was heard in V5 and ZS but, again, there wasn't enough sustained propagation for a contact. Southern Africa was a common opening during the 1989-1990 solar maximum so there is reason to hope for better next year.</p><p>The rest of the new countries were in many respects uninteresting yet challenging in their own way. There was J8, V2, V4, FJ, OA and other Caribbean, South America and Central America countries that found their way in my log this summer. It should be an easy shot from here but, like for many parts of the world, there is limited activity on 6 meters from many of those countries and few have big antennas or pay close attention to the band.</p><p>For TEP-enhanced equinox propagation to the south, the new ones this year were OA and VP8 in March. The latter was a difficult contact since he had difficulty copying stations. Perhaps the local noise was high. I am running out of unworked countries in South America other than the rare islands. Galapagos Island (HC8) was worked by many locals. My attention was elsewhere and I missed it.<br /></p><p>The final notable country was CY0S. That one was done on MSK144 meteor scatter. These were random meteors so it was very tough for everyone. A lucky few got through. We had no good sporadic E openings on this short path during the DXpedition.</p><p><b>Other stations heard and worked</b><br /></p><p>Although not a new country, I was pleased to work OX3LX on a
grid-pedition to northern Greenland. We don't often hear arctic stations
on 6 meters. Although I don't enthusiastically chase grids and islands, working these
unusual locations is always a pleasure.</p><p>There were numerous brief openings on long DX paths. Few delivered results but it was nice to hear them. These included:</p><ul style="text-align: left;"><li>Japan: only <a href="https://ve3vn.blogspot.com/2023/05/50313-share-what-you-hear.html">two stations worked</a>. This year was similar to the <a href="https://ve3vn.blogspot.com/2018/06/making-move-to-ft8-on-6-meters.html">first time</a> I briefly heard Japan but didn't work them. This time I was watching but this was all I could accomplish. There were other evenings with a few signals form JA netted no QSOs. Nothing else was heard from east Asia.</li><li>Central Asia: We had one fleeting opening to UN. That's typical for us. Last year's bounty of UN stations was very unusual. Two stations called me but signals faded before we could complete the contacts. PSK Reporter told me that I was heard in another country in the region but I didn't hear them if they called me.<br /></li><li>Indian Ocean: <a href="https://ve3vn.blogspot.com/2023/03/whet-appetite-6-meters.html">Early in the year</a> I heard 3B8, 3B9 and FR, and had a partial QSO with FR4OO. I was being heard, as seen on <a href="https://ve3vn.blogspot.com/2023/05/50313-share-what-you-hear.html">PSK Reporter</a>, but I wasn't always hearing them. It is likely due to a power difference.<br /></li><li>A scattering of other DX: 9K, Z6, TR, among others. The only one of these worked was 9K.<br /></li><li>W6: We had many openings to California this year. That's unusual. W6 isn't DX but a long path nonetheless. I worked some though most were stations I'd worked before. I pay close attention when I hear the southwest US and northern XE because they can herald openings to the Pacific, which are on the same western bearing.</li></ul><p><b>How can I do better?</b> </p><p>We are all <a href="https://ve3vn.blogspot.com/2016/08/6-meters-irritating-reality-of-magic.html">at the mercy of propagation</a>. We can monitor, let others know what we hear or toss a CQ into the aether. Bigger antennas and higher power can help. However, the several decibels you can glean that way pales in comparison to the far greater range of propagated signal levels. On the HF bands you can see results every day with a superior station because the propagation is more consistent.<br /></p><p>That <a href="https://ve3vn.blogspot.com/2021/04/station-improvements-for-6-meters.html">does not mean</a> station improvements are pointless. I already run the legal limit on 6 meters so all I can do is improve the antenna. I can replace the <a href="http://ve3vn.blogspot.com/2016/08/perils-of-chasing-yagi-performance-a50-6.html">optimized A50-6</a> with a bigger (longer boom) yagi or put another antenna higher up on one of my two big towers, and I may do so, even though that'll get me 1 or perhaps 2 db. </p><p>To go further I'd need a stack, both for gain and for a variety of elevation angles. That would require a new tower since I'm out of room on the ones I have. My priority is HF contests so VHF and other antennas must be placed wherever I can find room left for them. A new tower is unlikely since I'm not getting any younger and station maintenance will eventually become a burden.</p><p>I continue to consider the possibilities despite the obstacles. Since I'll soon sate my HF station objectives there will be time to devote to other projects. A long boom yagi in 2024 is a possibility. That's about all I can say at this point while I ponder the alternatives.</p><p><b>Closing note</b> <br /></p><p>I think this will be the last of my annual 6 meter reports. I've had a lot to report on for the past 6 years, and many seem to have enjoyed those articles. The rise of FT8 and FT4 was partly responsible due to its novelty and how it drew many hams to the magic band.</p><p>The <a href="https://ve3vn.blogspot.com/2022/08/6-meter-season-diminishing-returns.html">diminishing returns</a> I spoke about in the 2022 report about DXCC countries can now also be applied to these articles. There will continue to be individual articles on select topics about 6 meters, including notable propagation, new technology and station improvement, but not annual reports.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggLjDeBj13DOlGrqc1-87L_ARkoFCDoq5PdvRXo4mHo8B1TCt2zFd-aYRvPA2O-xe-RzwEnFjn9vPWp8rXY2CaxKbJPXuR35TYLbpp4xgC6zKXKfvTqySiR6ErW9GxtOcGruIb78MK01yOJgyEu_4bQ8NTb_PGyJUD3iLNmXb4MxCyIzQcOqBLivlxeEws/s499/6m_dx_20231019.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="499" data-original-width="311" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggLjDeBj13DOlGrqc1-87L_ARkoFCDoq5PdvRXo4mHo8B1TCt2zFd-aYRvPA2O-xe-RzwEnFjn9vPWp8rXY2CaxKbJPXuR35TYLbpp4xgC6zKXKfvTqySiR6ErW9GxtOcGruIb78MK01yOJgyEu_4bQ8NTb_PGyJUD3iLNmXb4MxCyIzQcOqBLivlxeEws/s16000/6m_dx_20231019.jpg" /></a></div><b><i><u>Update Oct.20, 2023:</u></i></b><p></p><p>My gloomy report about DX for the remainder of the year proves that my belated report ought to have been belated a little longer. I got an email alert on October 19 from the newest member of our <a href="https://ve3vn.blogspot.com/2021/10/6-meter-dxing-using-buddy-system.html">local 6 meter buddy group</a> (VE3KG) that stations from the Indian Ocean were rolling in.</p><p>Frantic activity followed, with most of us working 3B8FA, 3B8CW and 3B9FR. A few hours later I worked 7Q7EMH. But that wasn't all! That evening saw an excellent TEP opening to South American. I worked a number of Brazilian stations while my friends chased ZP9HTL, who I worked last year. Then today, October 20, VP8LP was worked by many stations in this corner of North America. </p><p>I guess the magic band still has a few surprises in store for us this year! It is remarkable considering that the solar flux index is hovering around 130. The key factor appears to be a rare October sporadic E opening bridging to TEP. Both days saw strong signals from VO1 and VY2, and later from W4.</p><p>It's a good thing someone in our group was checking 6 meters or I'd have missed all of it. The buddy system works.</p><p>3B8, 3B9 and 7Q are new DXCC countries for me, bringing my total to 134. My 2023 increment is now 14 countries. TO8FH (Mayotte) was heard by others nearby but not by me. That would have been a fine catch. I am no longer quite so gloomy about 6 meter prospects in the coming days and weeks.<br /></p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com0tag:blogger.com,1999:blog-6207999661586171874.post-44307412713445079592023-10-10T21:59:00.004-04:002023-10-10T22:00:31.338-04:00Inspecting a Bencher Skyhawk<p>This is not a typical product review. Indeed, it is really not a review at all. But as I inspected, cleaned, reassembled and installed the Bencher Skyhawk tri-band yagi I recently purchased <a href="https://ve3vn.blogspot.com/2023/08/preparing-for-fall-antenna-work.html">secondhand</a> I thought that it might be instructive to look at how an antenna ages and how it is designed. Nothing lasts forever, and problems crop up in the best antennas. They are totally exposed high up on a tower and endure everything nature can throw at them. </p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhvlSu7NK5LDoxrmNwiJ8bwPCKHkgs-LBYnZ6L7EoozkzazlREbUzonE2HjmtvdxzFAtR8bUFH6xcbgn290Pdq2E6ocpEln6rAVpW3Ly7uQFlQQVPL_o3daFN8cWXMl1JKoHuO7Mv6yUAgNAn2SljmhczbMFxMGI9_nO360yDCB7nVtspfwsjoZAGHWljD8/s640/skyhawk_on_trylon.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="605" data-original-width="640" height="379" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhvlSu7NK5LDoxrmNwiJ8bwPCKHkgs-LBYnZ6L7EoozkzazlREbUzonE2HjmtvdxzFAtR8bUFH6xcbgn290Pdq2E6ocpEln6rAVpW3Ly7uQFlQQVPL_o3daFN8cWXMl1JKoHuO7Mv6yUAgNAn2SljmhczbMFxMGI9_nO360yDCB7nVtspfwsjoZAGHWljD8/w400-h379/skyhawk_on_trylon.jpg" width="400" /></a></div><p style="text-align: left;">Mine is an approximately 12-year old <a href="https://www.eham.net/reviews/view-product?id=267">Bencher Skyhawk</a>, a product which has since been transferred to <a href="https://www.dxengineering.com/parts/dxe-3x10">DX Engineering</a>. The new owners have made only a few small changes so that the antenna you can buy today is substantially the same as the original. My observations are mostly applicable to both. </p><p></p><p>The electrical and mechanical design of this no-trap tri-bander is very good and reviews are almost all very positive. This is a fine antenna. That's why I bought it. But a 12-year old antenna is not a new antenna and time has taken its toll. That's one good reason you don't pay new prices for old merchandise. The resale prices of many products fall precipitously because they age poorly.</p><p>The Skyhawk is now on the air at VE3VN. Raising of the antenna was described in a <a href="https://ve3vn.blogspot.com/2023/10/rearranging-yagis.html">previous article</a>. <br /></p><p>This article contains my notes and observations. As already said, this is not a review but a collection of my impressions from inspecting, assembling and raising the antenna. It was an interesting study.<br /></p><p><b>Electrical design</b></p><p>A multi-band yagi is very difficult to design and optimize. This is true with or without traps. All the elements interact, so that even non-resonant elements, and even the tips beyond the traps, have induced current and their fields add to those of the resonant elements. There are no analytical solutions except in the most trivial of cases. </p><p>An iterative numerical process is needed to solve the design problem. Before computer modelling, trap yagis had to be refined with great time and expense on a test range. Many manufacturers didn't even bother trying. I've done manual iterations using EZNEC to optimize small yagis but large ones like the Skyhawk require automated algorithms. For my own antennas, I most often take an already optimized design, whether one band or more, which I may tweak to meet my personal performance objectives.<br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgRu1M6BP4H6cVE7TdKPNhR5ijEk5__kcDOJC7S6pOCAxUMvhYVgCyiSqJA-MV4l5O3Vq_W7mHWdkGJny2pjOjibt-EYRPDVtlPX_ex3RAkFgbhtuBSNMua8i_UjftMEqR5Wwnn9xAai9Ec5s98E9yG6ReTyJZxsrfbPEIENIOOY2_qTn8seV2NNPt2Gnxf/s937/skyhawk_swr_20-15-10.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="176" data-original-width="937" height="120" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgRu1M6BP4H6cVE7TdKPNhR5ijEk5__kcDOJC7S6pOCAxUMvhYVgCyiSqJA-MV4l5O3Vq_W7mHWdkGJny2pjOjibt-EYRPDVtlPX_ex3RAkFgbhtuBSNMua8i_UjftMEqR5Wwnn9xAai9Ec5s98E9yG6ReTyJZxsrfbPEIENIOOY2_qTn8seV2NNPt2Gnxf/w640-h120/skyhawk_swr_20-15-10.jpg" width="640" /></a></div><p> <u>Measurement notes</u>: The SWR plots were made with a RigExpert AA54 in the shack, through
about 40 meters of low-loss coax (except 2.5 m of RG213) and a 2×8
antenna switch. I checked the SWR at the feed point after it was raised but the measured impedance is affected by body proximity. The effect increases with frequency: little change on 20 but noticable on 10 meters.<br /></p><p>The Skyhawk is optimized and it is a good design. Although I have not developed a computer model of the antenna, nor have I read an engineering review of it, it appears from its behaviour that some gain may have been sacrificed in favour of an excellent match across all three bands.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi3Uq88bxkp_wFRb8e_uB9KPK2W4QWH98z3oOXD9bctOlamFyC7xJ1SetBrD-xZj_425VfHOhc7xeB7IDZmX7d7vrHk0usRaS9uP8_EVInzqaWYgY2GP7PU0oeoLGrELWokKsC72zfrDu0jj_T29fudOp31SY-5rhC-pVoITo37kFgT-eehL_7e-MO1Syxh/s533/skyhawk_prep_major_pieces.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="533" data-original-width="400" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi3Uq88bxkp_wFRb8e_uB9KPK2W4QWH98z3oOXD9bctOlamFyC7xJ1SetBrD-xZj_425VfHOhc7xeB7IDZmX7d7vrHk0usRaS9uP8_EVInzqaWYgY2GP7PU0oeoLGrELWokKsC72zfrDu0jj_T29fudOp31SY-5rhC-pVoITo37kFgT-eehL_7e-MO1Syxh/w300-h400/skyhawk_prep_major_pieces.jpg" width="300" /></a></div><p style="text-align: left;">There's nothing wrong with that and it may be better for the majority. I tend to favour a little more gain. But that's a nitpick.</p><p></p><p><b>12 years of wear</b></p><p>Nothing lasts forever, and that includes antennas. Exposure to the elements takes its toll no matter how good the antenna's mechanical design. An inspection found problems, both small and large. These were corrected before it was reassembled and raised.</p><ul style="text-align: left;"><li>Rivets<br /></li><li>Driven element spacer</li><li>Grease <br /></li></ul><p>I laid out the pieces of the antenna on the deck to do the inspection and element assembly. Rivets had to be removed from several elements to break into sections that would fit on the truck. </p><p>It was an excellent opportunity to inspect how rivets perform over time. I was interested because I've never owned a yagi that used rivets and I didn't use them on my many home brew antennas.</p><p><b>Rivets </b><br /></p><p>Rivets have always struck me as inadequate for joining the sections of tapered element since they are quite small. I wondered if they were strong enough to last and whether the longitudinal stress on the element would accelerate failure of the softer aluminum alloy tubes. Disassembly of the antenna for transport gave me an opportunity to inspect their long term behaviour.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiG1yZohPPm0HEgPMbene0PqKwer9otyal7v_a1mVZv9eHVdUtP4aZ4SOd8C2U1Wp8NoGuVjsvm_hQwh3CtzRQt3L9i1MJnzHqSpr1d2WgSin6xgsBQhZyQHWfngKoIZrbwwRTVSqaddy3zpOiUvoq0EZWuLQho66vRZ7YPflel73zKaXKrHH5pPy-hqbca/s821/skyhawk_rivet_damage.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="359" data-original-width="821" height="280" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiG1yZohPPm0HEgPMbene0PqKwer9otyal7v_a1mVZv9eHVdUtP4aZ4SOd8C2U1Wp8NoGuVjsvm_hQwh3CtzRQt3L9i1MJnzHqSpr1d2WgSin6xgsBQhZyQHWfngKoIZrbwwRTVSqaddy3zpOiUvoq0EZWuLQho66vRZ7YPflel73zKaXKrHH5pPy-hqbca/w640-h280/skyhawk_rivet_damage.jpg" width="640" /></a></div><p style="text-align: left;">On the left is an improperly seated rivet head. I drilled out several of these to inspect the holes and insert new rivets. There was no obvious damage to the tubes or rivets in most cases so the protruding heads were likely due to mishandling of the rivet tool. The heads of all the rivets protrude around most of their circumference since it's flat and the tube is cylindrical. That isn't ideal but it seems to work.</p><p></p><p>On the upper right is a damaged hole where rivets were drilled out to disassemble the element. The sides of the hole are clean so it is possible that it was due to careless application of the drill. I left it as is and inserted a new rivet. The resulting bond was good since the rivet head is larger than the hole in the outer tube and the inner tube wasn't damaged.</p><p>Close inspection of the inner tube of one telescoping joint was enlightening. The hole is longitudinally elongated and the inside hole rim is roughly bevelled. The elongation is slight, probably no more than 0.020", and it is sometimes less (my calipers didn't fit very well for accuracy). This is what I expected since mechanical stress on the element is primarily longitudinal. </p><p>The ⅛" diameter of the stainless rivets is a small, hard surface that can amplify the stress and push the softer aluminum aside. However, it isn't enough to be of concern so I inserted new rivets and continued.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjLprG_H_nfv_pobzt2UBZ4OdXEF1MelnJDoYnMTqHtbdnhARaVkTclf3bc3fv2JUiaPKGrXvwpl-iY9myayESIKqpA675gu6IxiPFHObp0AUkfNrY3oZsEZ5aWblUcNDlJJzuiA5IiIQcKrKmNfsiFb2ymRkznMXNvpurUyZNl1wmCMFk0T70VvWwACc1u/s400/rivet_tube_gap.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="219" data-original-width="400" height="219" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjLprG_H_nfv_pobzt2UBZ4OdXEF1MelnJDoYnMTqHtbdnhARaVkTclf3bc3fv2JUiaPKGrXvwpl-iY9myayESIKqpA675gu6IxiPFHObp0AUkfNrY3oZsEZ5aWblUcNDlJJzuiA5IiIQcKrKmNfsiFb2ymRkznMXNvpurUyZNl1wmCMFk0T70VvWwACc1u/w400-h219/rivet_tube_gap.jpg" width="400" /></a></div><p style="text-align: left;">The outer diameter (OD) of the smaller telescoping tube is less than the larger tube's inner diameter (ID). In both cases the wall thickness is 0.058", which is the most common US made aerospace alloy tubes used for telescoping yagi elements in ⅛" steps. For a press fit the wall would have to be 0.0625". That leaves a maximum gap of 0.009" when the tubes touch on one side. The tubes thus slide together very easily. Please note that the gap is less than it appears in the pic due to shadowing.</p><p></p><p>The antenna obviously works well despite the gap, although it bothers me a little. A press fit a poor choice for antennas since if you could insert the smaller tube it'll probably never come out again! Oxidation, stress and galling take their toll. For full circumference contact the outer tube must be slit and a gear clamp used to squeeze them together. That introduces two points of failure: the slit and the clamp. High quality stainless clamps are essential for reliability.</p><p>There are other ways of bonding telescoping tubes. A <a href="http://ve3vn.blogspot.com/2019/10/aluminum-yagi-construction-materials.html">few of those</a> which are applicable to element tubes were described in the blog when I was building my many yagis. Each method has its pros and cons, including rivets. Perhaps rivets aren't so bad after all.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZ5xR2jfD8R5owpmT7wVokY67oE2uuKh2s2563223nmgI6hxzSqP0kou_85XMtaHBb7z8WxHXBk9E3n8y3z4d4IreEEO1sNEuAeMhs9PjAotH6nsNgaUNTXyBwJAEiPHINmUTFGbDo5uLuAWzKCpdIkO29zfjIgSLpoE1cYQrEkQyiIzvMCZu1df4NC27j/s944/skyhawk_rivetting.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="318" data-original-width="944" height="216" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZ5xR2jfD8R5owpmT7wVokY67oE2uuKh2s2563223nmgI6hxzSqP0kou_85XMtaHBb7z8WxHXBk9E3n8y3z4d4IreEEO1sNEuAeMhs9PjAotH6nsNgaUNTXyBwJAEiPHINmUTFGbDo5uLuAWzKCpdIkO29zfjIgSLpoE1cYQrEkQyiIzvMCZu1df4NC27j/w640-h216/skyhawk_rivetting.jpg" width="640" /></a></div><p style="text-align: left;">There are many online resources that explain rivets and how they work, and how to use them. High tensile strength stainless rivets are inexpensive and widely available. It's well worth wasting a few to practice using the rivet tool. I drilled a few ⅛" holes in scrap aluminum and practiced until I was sure of what I was doing. The rivet tool came with the antenna.</p><p></p><p>It takes a lot of force to seat the rivet and break the narrow neck. I found it easiest to place the element and tool on a solid surface and press the upper handle with one hand while using my other hand to align the tool head with the tubes and to ensure contact between the rivet head and the tool tip. Inset is a closeup of properly seated rivets that were drilled out. You can see how the rivet bulb expands the shank upward to squeeze the tubes together against the rivet head.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjzJennMHyyJ6DNi_ByPWgODj3IBhPQ37BPQEEAaNR7sUxMm3u_W537ip_ObG3JJU2LvEql493R_rA9ucPYESp1tkYyrjGOPrIIREZDY2twDomQFHWh6P7XaRX33GFgEUaG68iM7WqwG0kWCJBl14RvcHO60HM8bGHVitoAqjMpMpUM7-J7jhIwlkjSu7s8/s947/noalox.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="947" data-original-width="387" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjzJennMHyyJ6DNi_ByPWgODj3IBhPQ37BPQEEAaNR7sUxMm3u_W537ip_ObG3JJU2LvEql493R_rA9ucPYESp1tkYyrjGOPrIIREZDY2twDomQFHWh6P7XaRX33GFgEUaG68iM7WqwG0kWCJBl14RvcHO60HM8bGHVitoAqjMpMpUM7-J7jhIwlkjSu7s8/w82-h200/noalox.jpg" width="82" /></a></div><p style="text-align: left;">All conductive joints in a yagi should be coated to prevent oxidation, prevent binding of telescoped tubes and assure conduction. Many hams skip this step and they should not. I've taken apart many "dry" antennas that required restoration. Some use dielectric grease, and it can work well if it doesn't dry out. A better choice is a conductive grease, which is essentially dielectric grease with a suspension of microscopic metal particles.</p><p></p><p>The manual states that the Bencher product was shipped with a product called Butter-It's-Not. The name is familiar but I've never seen it and I had difficulty searching for it online -- searches favour links to margarine sites! In any case there are many products. Whatever was used on my Skyhawk, all the grease had dried, leaving a residue of the suspended metal and whatever else. From the residue at least two different products were used.</p><p>I lightly sanded the exposed joints to renew them and greased them. Rivetted joints were left as is. The product I use is Noalox. I've had good success with it. The joints remain slippery after many years. I know there are better products that I have less experience with so don't take this as a firm recommendation. My squeeze bottle is so old that the plastic is cracked and repaired with clear packing tape. I've greases joints in countless antennas over the years. A small amount goes a long way. It's cheap insurance so don't skimp.<br /></p><p><b>Driven element spacer</b></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgTCGuf3xihubSstnNF_ZNqGyPVSSYmjvUMaWRkq5iiuz8NmdCIS_cR6a3I_YFID6suL2kP5PEsV_GSLQITReEh3VaSf6KgJ2wqeqRoDg2-SpYPpghRn8k-YM1oDVDmPb4AOjYFSemNfNCNvWyX9qQM9zhvnuDTnxrzpFyxVyBwi7HX8umODeXl7UTj2b1m/s360/skyhawk_cracked_spacer.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="261" data-original-width="360" height="232" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgTCGuf3xihubSstnNF_ZNqGyPVSSYmjvUMaWRkq5iiuz8NmdCIS_cR6a3I_YFID6suL2kP5PEsV_GSLQITReEh3VaSf6KgJ2wqeqRoDg2-SpYPpghRn8k-YM1oDVDmPb4AOjYFSemNfNCNvWyX9qQM9zhvnuDTnxrzpFyxVyBwi7HX8umODeXl7UTj2b1m/s320/skyhawk_cracked_spacer.jpg" width="320" /></a></div><p style="text-align: left;">Feeding multiple elements directly from a common feed point puts them in close proximity. Without one or more spacers along their lengths the driven elements would strike one another when the wind is more than a light breeze. That would be catastrophic since the transmitter would fault due to SWR when they make contact.</p><p></p><p>The Skyhawk uses one spacer on each side of the boom to hold the three driven elements. Only the 15 and 20 meter elements are at risk of touching, and that's very unlikely unless the tubes are severely stressed. If wind or ice of such severity were to occur, you'd likely have bigger worries!</p><p>A common complaint in many online review of the antenna is that over time the bundle of driven elements develops an S curve. The reason is that the spacer gradually slides sideways on the 10 and 15 meter driven elements while waving in the wind. When it slides it tends to stay in its new position because the tube fit is tight. Only on the 20 meter element is the spacer trapped so that it can't move. </p><p>The plastic spacer is very tough but not indestructible. Apart from the unsightliness of twisted elements, the spacer and tubes are placed under increased stress. You can see where one of the spacers cracked, not surprisingly on the 20 meter element where the hole in the spacer is largest. I'm surprised that this product flaw has not been resolved.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiybkKltkhHpOhFk8Z83lfJ7WiDUXs_G6hH8G_E-mwCPfaaOI3MjgFZbbyZaxJAUFx9Stf3Z_no_maygdeD6dL6uJn_Ks-BYtX08Y4O_F99HTf20SwJUuPmwySyjq0if_Hi9gRNtv7bLVTpRx60rNpAg2mpejusJx1vXb79CroObXE3feHdZWo6GUs0VQPI/s640/skyhawk_spacer_stabilization.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="218" data-original-width="640" height="218" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiybkKltkhHpOhFk8Z83lfJ7WiDUXs_G6hH8G_E-mwCPfaaOI3MjgFZbbyZaxJAUFx9Stf3Z_no_maygdeD6dL6uJn_Ks-BYtX08Y4O_F99HTf20SwJUuPmwySyjq0if_Hi9gRNtv7bLVTpRx60rNpAg2mpejusJx1vXb79CroObXE3feHdZWo6GUs0VQPI/w640-h218/skyhawk_spacer_stabilization.jpg" width="640" /></a></div><p style="text-align: left;">My solution was to fix the spacer position on the 10 and 15 meter elements. A combination of small hose clamps and UV-resistant cable ties are lightweight and get the job done. It takes very little resistance to prevent the spacer from creeping.</p><p></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjg4vTajSpbU4ICMPgcptavNGWQ4i9ObWDo7A0h9gEcfJtvNe136gPQ7wFr1GuAvO2SiUP_G23LDgxpGW1AmWhNCJYoovLMh9Br9f8IUryBTjaJj1UozXXnybC9IbeNE_vYYdkdu5jkU9kpoAdhH2A9GNv9QUwMcw5y4_if6MwJIeT_81e4EBxtDS_vEAE0/s300/skyhawk_spacer_repair.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="219" data-original-width="300" height="219" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjg4vTajSpbU4ICMPgcptavNGWQ4i9ObWDo7A0h9gEcfJtvNe136gPQ7wFr1GuAvO2SiUP_G23LDgxpGW1AmWhNCJYoovLMh9Br9f8IUryBTjaJj1UozXXnybC9IbeNE_vYYdkdu5jkU9kpoAdhH2A9GNv9QUwMcw5y4_if6MwJIeT_81e4EBxtDS_vEAE0/s1600/skyhawk_spacer_repair.jpg" width="300" /></a></div><p style="text-align: left;">I ventured to repair the cracked spacer rather than order a replacement. I drilled a hole and threaded a heavy duty cable tie through it. The tie braces against the element to bind the sides of the crack. </p><p></p><p>When kept in the correct position, the radial stress ought to be low. The plastic itself is quite tough (it survived the crack). Time will tell whether my repair is effective.</p><p><b>Element-to-Boom clamps<br /></b></p><p>The element-to-boom clamps have no way to fix the element centre to coincide with the boom. All the elements are insulated from the boom with bonded plastic sleeves and you simply judge by eye (or a ruler) as you tighten the clamp bolts. Perfect centering is irrelevant to performance but I do it anyway.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjmUdIKvlAHndASdnAD1c4fLp6RMx7xvP0_XL3eI-fod8GfJBBLrY4172_u9_EIHx4TWCG0nSSDGZhsjZZrsgt5hUxPLg4ICO4x6faK-t73Xl6_vjPa0wCSRUj5xX64et9pmrXdQ1qArEN-PslEKV-sJfTAWnqJj61mkSwnSmfCuDnhPtNUh3eHoOoEyDUL/s577/skyhawk_feedline_from_dxe_manual.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="263" data-original-width="577" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjmUdIKvlAHndASdnAD1c4fLp6RMx7xvP0_XL3eI-fod8GfJBBLrY4172_u9_EIHx4TWCG0nSSDGZhsjZZrsgt5hUxPLg4ICO4x6faK-t73Xl6_vjPa0wCSRUj5xX64et9pmrXdQ1qArEN-PslEKV-sJfTAWnqJj61mkSwnSmfCuDnhPtNUh3eHoOoEyDUL/s16000/skyhawk_feedline_from_dxe_manual.png" /></a></div><p style="text-align: left;">The driven element clamp alignment is more critical (picture is from the DXE manual). These three elements are split for feeding. Rather than one long plastic sleeve, there's a short one on each side of centre. The straps for feeding the elements in parallel are wide and carelessness can cause a short between the strap and the element clamp (which contacts the boom). I made sure the clamps were properly tightened to prevent the elements from creeping due to wind stress. </p><p></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiASClB_xsOc0z7YhWW1_6D-T_5CUZhkVPq17ITFzybyDd09LxN3xYHJSKkqwHjjr66YwKzG5hRyjCeoV9z6fies4hRsoxWyKCHC66v3G1gFj6zmWfZxukSicIPrEqhcpg93nGF6ejb2MXGH1Ghbf8TL8kfym0FhDK4xf1uxp5ANtSXfT0NIGyNhQEzJd8v/s640/skyhawk_compensators.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="640" data-original-width="480" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiASClB_xsOc0z7YhWW1_6D-T_5CUZhkVPq17ITFzybyDd09LxN3xYHJSKkqwHjjr66YwKzG5hRyjCeoV9z6fies4hRsoxWyKCHC66v3G1gFj6zmWfZxukSicIPrEqhcpg93nGF6ejb2MXGH1Ghbf8TL8kfym0FhDK4xf1uxp5ANtSXfT0NIGyNhQEzJd8v/w300-h400/skyhawk_compensators.jpg" width="300" /></a></div><p style="text-align: left;">I wish the design of the feed and clamps were better. However, I haven't heard any complaints on various fora of shorts developing over time. It must happen but perhaps it's rare. A raised lip or rim on the inner side of the sleeve would reduce the risk.<br /></p><p></p><p>Another peculiarity (or benefit) of the clamp design is that there is no way to position or align the elements along the boom. There is a bolt that run through the upper half of the clamp and the boom. In a few cases the bolt does double duty to bond the boom sections and the boom compensator. <br /></p><p>Alignment was excellent except for the driven elements. They are less than 2° askew. It isn't noticable except when you sight along the boom. The PVC element compensator doesn't age well so it is no longer straight. That isn't the fault of the clamp, and it doesn't matter.<br /></p><p><b>Boom attachments<br /></b></p><p>The antenna has no boom truss despite its 24' length and with the longest (heaviest) 20 meter elements mounted at each end. Despite that lack the boom is pretty hefty and sags very little. You can get an idea from the view along the boom towards the reflector end.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhBH9vQN471lQaQSfQ-bUnHiF0jUcYPZs3SMS8oWZY5Ey-jpN59rsDF73vYQF9WWt652RmYnrY4cbDHxbr6rNlDNk6m8D63sJETjaY1sVlFRKhpOQU83Z9ZTjFwjG3ursLTtMb2tuctFIYjtUCSmFtoWS9OxgRpfm0dzB5zftLcOoiyVe-GOcsxZjsBGg7c/s800/skyhawk_boom_droop_rear.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="507" data-original-width="800" height="406" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhBH9vQN471lQaQSfQ-bUnHiF0jUcYPZs3SMS8oWZY5Ey-jpN59rsDF73vYQF9WWt652RmYnrY4cbDHxbr6rNlDNk6m8D63sJETjaY1sVlFRKhpOQU83Z9ZTjFwjG3ursLTtMb2tuctFIYjtUCSmFtoWS9OxgRpfm0dzB5zftLcOoiyVe-GOcsxZjsBGg7c/w640-h406/skyhawk_boom_droop_rear.jpg" width="640" /></a></div><p style="text-align: left;">You really don't notice it from the ground. Aside from aesthetics there is a question of how much severe weather load the boom and mast clamp can tolerate without the truss. The antenna is engineered for high winds and some ice so I am not especially concerned. But I do wonder how it'll fare in our harsh winters and occasional severe ice storms. On the other hand, elimination of the truss keeps the mast free of obstructions.</p><p></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhax_dFj9WXKE6bwre3L1IRDn-L_zHy_PBjGYvltLOUOq5TcqP8bOfS5aU2PPM_U_XUIU3hNkatm0J19dM6BzEP4aR_3Tv3_xXjtxmHJbRuMGKSHFtjUTbojUAqEk-cJ6-ty3g6BMJSio-E2k5qBalak8wHc9LdmM3JgNeYIUQwbMLsq7ImINVTuc52iSzB/s533/skyhawk_boom-to-mast_clamp.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="533" data-original-width="400" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhax_dFj9WXKE6bwre3L1IRDn-L_zHy_PBjGYvltLOUOq5TcqP8bOfS5aU2PPM_U_XUIU3hNkatm0J19dM6BzEP4aR_3Tv3_xXjtxmHJbRuMGKSHFtjUTbojUAqEk-cJ6-ty3g6BMJSio-E2k5qBalak8wHc9LdmM3JgNeYIUQwbMLsq7ImINVTuc52iSzB/w300-h400/skyhawk_boom-to-mast_clamp.jpg" width="300" /></a></div><p style="text-align: left;">When I removed the antenna from its previous owner's tower I was unfamiliar with the design of the mast clamp. I automatically loosened the saddle clamps and sent the antenna into the hands of the ground crew below. The u-bolts don't pierce the saddles so it isn't difficult to drop the loose saddles.</p><p></p><p>I later came to understand the two-part design. The mast side of the assembly can be left on the mast for both raising and lowering. The upper nuts on the boom side of the clamp fit into the keyholes of the mast plate and drop into the slots below. When that's done the antenna is secure. The lower nuts can be threaded on and all 4 bolts tightened. The reverse procedure is performed for removal of the yagi.</p><p>Keyhole mounts are found on all types of hardware, but this is the first time I've seen it on a yagi. I like it. </p><p>When we raised the antenna onto my tower, the mast clamp was already installed and all I had to do was direct the nuts into the slots and have the crew lower the antenna an inch. There was no fussing with multiple saddle clamps (often with short u-bolt legs that require near perfect alignment) to secure the load. </p><p><b>Balun and coax</b></p><p>The balun supplied by Bencher is more compact than the one included by DX Engineering. It appears to have weathered well. I can't say how well the PVC electrical box for DX Engineering's common mode choke will survive other than to note my <a href="https://ve3vn.blogspot.com/2023/06/perils-of-pvc.html">poor experience</a> with the same enclosure used by Balun Designs.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgbrvkWqwhW5hf2rOnDTtPZco-L2ZLlC3GFzgcJicFHYNWlHCHp5SjegQUDBNyWfMtH6Q1WJ3LfDUw-Bj5M20uel4vwgN_CWQpCWeonipZ9rMM7mwGUETb_foCQA-UpLmzSS2hzJx3hSFKQfAWu6OpADjSohmvkN8tS7UsAzaSYePT19AbQClxhGA3PtUJN/s640/skyhawk_balun.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="210" data-original-width="640" height="210" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgbrvkWqwhW5hf2rOnDTtPZco-L2ZLlC3GFzgcJicFHYNWlHCHp5SjegQUDBNyWfMtH6Q1WJ3LfDUw-Bj5M20uel4vwgN_CWQpCWeonipZ9rMM7mwGUETb_foCQA-UpLmzSS2hzJx3hSFKQfAWu6OpADjSohmvkN8tS7UsAzaSYePT19AbQClxhGA3PtUJN/w640-h210/skyhawk_balun.jpg" width="640" /></a></div><p style="text-align: left;">The balun fits snugly under the boom using special brackets to keep it centred and with adequate space for fitting and weather proofing the coax. I tested it with a dummy load on the workbench and it tested fine, with inductive reactance gradually increasing with frequency due to the pigtails. I do not have a fixture for testing common mode rejection. The quantity and type of ferrite beads determine its performance.</p><p></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhle2vxgTpDtiJvM_c9tqg0cGnJbj4ol9xTQJHoiBXVd-iJIqaR9WfNf1Ks6m5VLcoGfDxf02u5WDtzDYn6Ze9n487wZhwQ9imd4VR-vu2FkFzrYlsEPXrMTq1bteSCX_vpGiArq916Yo_EvCgjIo0064tdZa_jqX0pWSeqwdQ1vmCZtgEFArf7NixtuOYO/s640/skyhawk_feedpoint.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="383" data-original-width="640" height="384" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhle2vxgTpDtiJvM_c9tqg0cGnJbj4ol9xTQJHoiBXVd-iJIqaR9WfNf1Ks6m5VLcoGfDxf02u5WDtzDYn6Ze9n487wZhwQ9imd4VR-vu2FkFzrYlsEPXrMTq1bteSCX_vpGiArq916Yo_EvCgjIo0064tdZa_jqX0pWSeqwdQ1vmCZtgEFArf7NixtuOYO/w640-h384/skyhawk_feedpoint.jpg" width="640" /></a></div><p>The location of the feed point is not convenient for attaching the coax and rotation loop. The Skyhawk includes a boom bracket to support the coax and thus reduce stress on the connector and balun. Unfortunately, that puts the coax even further out. It isn't very far but you must be comfortable leaning out from the tower to do the work.</p><p>Since the feed system is below the boom the coax is routed above the boom. The rotation loop is located on the opposite side of the mast and paired with coax dropping down from the 6 meter yagi at the top of the mast. It is possible to put the rotation loop on the same side of the mast by routing it down on the outside of the driven elements, except that the coax has to be kept rigid as it passes the balun to avoid jostling during rotation. A few more feet of coax makes a cleaner rotation loop on the far side of the mast, so that's what I did.</p><p><b>Tube caps</b></p><p>The antenna comes equipped with plastic caps for the boom and element tips. Only a few of the elements had caps on my Skyhawk. I prefer no element caps so that water can freely flow out should any get in. </p><p>I have the boom caps and I put them on. Insects are a greater risk in booms since they are large. It's a trade off. Depending on local conditions it maybe sensible to cap all of the tube ends, or none of them.<br /></p><p><b>So far...</b></p><p>I'm happy with the Skyhawk. The first contact was with VK9LAA and I have made many other DX contacts since, including several of the current DXpeditions. It's easier and quicker to turn this antenna than the prop pitch driven big yagis. Although it is not my best antenna on the high bands, it is usually sufficient to make the contact. The agility it brings to my contesting is very welcom. </p><p>For most hams it would be a fine antenna on its own. Just make sure the tower and rotator are up to the job. There are many elements and that adds up to a high wind and ice load. </p><p>Another consideration is the price. There are few antennas I would buy new and this one is no exception. Material prices have skyrocketed over the past few years and that makes up a substantial portion of the manufacturing cost. The Skyhawk is not out of line with the prices of similar antennas. I don't see many available on the used market. I buy my antennas used or I build my own, with infrequent exceptions.<br /></p><p>Direct comparison with the TH6 hasn't yet been done since their gains will be close and the confounding factors many. 1 to 2 db of difference is difficult to reliably discern by ear or S-meter on receive. On transmit it's a different matter: the extra gain of a no-trap design <i>will </i>be noticed. This is often also true when comparing my stacks to smaller yagis. The contest pile ups are deeper and they last longer.<br /></p><p>Most hams are fortunate to have one yagi for the HF bands, and two is uncommon. Easy comparisons are impossible. Hence the reliance by some hams on myth and lore, unreliable opinions and advertising. We do have a tendency to convince ourselves that whatever choice we make is the best choice because it is our choice. Physics begs to disagree.</p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com0tag:blogger.com,1999:blog-6207999661586171874.post-51240504077541136482023-10-05T20:57:00.004-04:002023-10-05T20:58:11.629-04:00Rearranging Yagis<p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjajBsOsUFTUCaNXAQeIvhREU3G2CseSyya9Gbd5iUuD9oKhq5CDVd3EeeVohmEIpUv1dEH7zp_4MX0gAq6CVVKQPWDLRn180FhJwRmv704aA_2KBcNxcaXDtadJN6_IKCQn2QqQVte_1bp0mIHakZm7iWtxnMOAcMjNgfZ_4Rstvw4syx8Dk6gg90GUwxN/s755/xm240_th6_lr20-1_202310.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="755" data-original-width="360" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjajBsOsUFTUCaNXAQeIvhREU3G2CseSyya9Gbd5iUuD9oKhq5CDVd3EeeVohmEIpUv1dEH7zp_4MX0gAq6CVVKQPWDLRn180FhJwRmv704aA_2KBcNxcaXDtadJN6_IKCQn2QqQVte_1bp0mIHakZm7iWtxnMOAcMjNgfZ_4Rstvw4syx8Dk6gg90GUwxN/w306-h640/xm240_th6_lr20-1_202310.jpg" width="306" /></a></div><p style="text-align: left;">No long ago, I described that during <a href="https://ve3vn.blogspot.com/2023/08/preparing-for-fall-antenna-work.html">this fall's antenna work</a> several yagis would be moving or removed. You can see a graphic of the plan in that August article. Here it is in words:</p><p></p><ul style="text-align: left;"><li>Remove the TH6 from the <a href="https://ve3vn.blogspot.com/2021/09/side-mount-for-limited-rotation-yagi.html">rotatable side mount</a> halfway up the 150' tower</li><li>Move the XM240 from the Trylon to the position vacated by the TH6</li><li>Raise the <a href="https://ve3vn.blogspot.com/2023/08/preparing-for-fall-antenna-work.html">recently acquired</a> Bencher Skyhawk onto the Trylon</li></ul><p>Later in the article I'll discuss why I'm doing this. But first I'll describe what was done.<br /></p><p>Not including preparation and cleanup, the latter two items were accomplished in one day with the help of Alan VE3KAE and Dave VE3KG. I had hoped for one more helper but we made for it with mechanical muscle.<br /></p><p>Since making my annual plan, I had a change of heart and the TH6 was moved rather than removed. I spent a couple of hours in the workshop to make a fixed bracket for the big tower. I installed it a little above the rotatable side mount. With Alan's help a week earlier we lifted the TH6 the short distance to its new perch. It is fixed to the south (170°). It's been here <a href="https://ve3vn.blogspot.com/2019/09/one-step-forward.html">before</a>. That freed the rotatable side mount for the XM240.<br /></p><p>I have written so much in this blog about the various methods for raising yagis that I won't repeat myself. Do a search of the blog and you can read all about tram lines, tag lines, pulleys, vehicle power and much more. One picture will suffice for this article, of Alan posing with the XM240 at the tram line's launch point.<br /></p><p>The only significant difficulty was on the smaller tower, the 70' Trylon. Being close to the house rather than in the middle of a hay field like most of my towers, there are obstacles. The yard area of my large property is very pretty with many trees, but they pose a challenge for raising and lowering antennas. For one thing, they grow! The challenge increases every time I lift or lower a yagi.</p><p></p><p style="text-align: left;">The XM240 and Skyhawk are quite large. Each weighs about 75 lb; the original XM240 is lighter but this one has been strengthened per W6NL. The antennas must land or be lifted a distance from the tower so that the elements and boom clear the <a href="https://ve3vn.blogspot.com/2022/12/overhead-cable-run-version-2.html">overhead cables</a> and several large and growing larger trees. Steering with tag lines is critically important. Finesse is needed more than brute strength, however the latter is needed when the yagi is close to the ground and far from the tower base.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-FM5nqUJI_X8grSYHm4_DyqtZXLgn3D4iYkzMv3hTOWIb9vHOUGCvT7wc_zeIYXtxiMhkr2FCzPnoInHXr-eqXf0Cj02r5i8o_JS6hLbWE2gNOn0O4xxw71tHX8WmvKBLag7nHzTKKD9My87mdpzWMM_KPmLgrkbZp0_hu0QkQC8uQC__YZsYfs48TSda/s800/xm240_tram_and_ve3kae.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="500" data-original-width="800" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-FM5nqUJI_X8grSYHm4_DyqtZXLgn3D4iYkzMv3hTOWIb9vHOUGCvT7wc_zeIYXtxiMhkr2FCzPnoInHXr-eqXf0Cj02r5i8o_JS6hLbWE2gNOn0O4xxw71tHX8WmvKBLag7nHzTKKD9My87mdpzWMM_KPmLgrkbZp0_hu0QkQC8uQC__YZsYfs48TSda/w640-h400/xm240_tram_and_ve3kae.jpg" width="640" /></a></div><p></p><p></p><p></p><p style="text-align: left;">I will emphasize one very important lesson about tag lines. Steering a yagi requires two tag lines, one on either side of boom centre. They are either attached outside an element clamp or prevented from sliding with a clamp or other means, and be easy to remove once the yagi is attached to the mast. </p><p style="text-align: left;">Two tag lines sounds like a job for two hams. Wrong! No matter how many times I have tried it over the years with two people, it is almost always impossible for them to perfectly coordinate their actions and intentions. If you don't believe me, try it. But try it with your yagi and not mine! Element tips are fragile.<br /></p><p></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgH9KRFxnLjyp6fFs5X0FSvSgXDmHKcJxzf1T5Eu8q6SqvHFgB0ma8kERlpth78TZJ5tDxYQhHoKNRgIINHjPGdwGiMo1Rq4q5zSVZzo1f7AFzCaTm4Uyn-BV8quvOpo34Q-tch-ap7t7SdsW7ymcdiscWq-joOTKofA2DSvQ22amZs0Mom6YXvI7ACOGSN/s895/skyhawk_on_trylon_full.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="895" data-original-width="360" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgH9KRFxnLjyp6fFs5X0FSvSgXDmHKcJxzf1T5Eu8q6SqvHFgB0ma8kERlpth78TZJ5tDxYQhHoKNRgIINHjPGdwGiMo1Rq4q5zSVZzo1f7AFzCaTm4Uyn-BV8quvOpo34Q-tch-ap7t7SdsW7ymcdiscWq-joOTKofA2DSvQ22amZs0Mom6YXvI7ACOGSN/w258-h640/skyhawk_on_trylon_full.jpg" width="258" /></a></div><p style="text-align: left;">Instead we divided the work. One person drove the vehicle for lifting and lowering power, one controlled <i>both </i>tag lines and the third person relayed communications between the driver and the handler of the tag lines. </p><p style="text-align: left;">The latter job went to me since I have the most experience with the delicate matter of steering yagis. I was also highly motivated since it would be my own yagis at risk! Communications was key since the vehicle was in the driveway and out of sight of us, and the driver could not see the tower or the yagi (trees and house blocked the view). </p><p></p><p>It was entertaining and tense at times but we got it done without damaging the antennas. For added excitement, we had to avoid bumping the wireless internet radio mounted near the top of the tower. Knocking it out of position would involve a costly service call. </p><p>I climbed the tower once to uncouple the XM240 from the mast and again to attach the Skyhawk to the mast, all while the vehicle was holding the yagi's weight. I won't get into the rigging details since, even with pictures, it is likely to be more confusing than enlightening. The rigging allowed the vehicle (my lawn tractor to lower the XM240 and a car to raise the Skyhawk) to move in a wide compass of directions while the line going up the tower stayed in a fixed position where it was clear of trees, tower and internet radio.</p><p>The pictures show the successful results. The antennas checked out and I <a href="https://ve3vn.blogspot.com/2023/01/station-automation-first-contest.html">reconfigured my software</a> to reflect the changes. To my chagrin, that uncovered a couple of bugs that I tracked down and successfully fixed that same evening. </p><p>Over the next several days I finished the job of boom trusses, dressing cables and weatherproofing. Late September and the first days of October were unusually warm and sunny. Temperatures soared to 30° C. That's record breaking for our northern climate at this time of year. </p><p>As I write this, the one outstanding task is hooking up the TH6. The Heliax is connected by I still have to reconfigure the antenna switches to free a port for it. Other than that, the XM240 and Skyhawk are fully operational and being used on the air. It's auspicious that my first QSO with the Skyhawk was VK9LAA. <br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0y2BU9UIsDR4dCLu4Y9giD_3hH6JkCOP3KpAStY47tDXRF2xrrMwBIwqpOjW9g7fJjhTGcEyO9lP7khoZO8eugr3z94yqndyUfcygUhKrHcgVW2gH8KqbpLDKy0p-rMoGIWRNFlkzukzld4zIktlIFdYTVqQ_QK5j2OTCLpHQBdJ4_cDs-zWy1xuOg3gg/s198/heliax_1000yd_knot.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="184" data-original-width="198" height="184" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0y2BU9UIsDR4dCLu4Y9giD_3hH6JkCOP3KpAStY47tDXRF2xrrMwBIwqpOjW9g7fJjhTGcEyO9lP7khoZO8eugr3z94yqndyUfcygUhKrHcgVW2gH8KqbpLDKy0p-rMoGIWRNFlkzukzld4zIktlIFdYTVqQ_QK5j2OTCLpHQBdJ4_cDs-zWy1xuOg3gg/s1600/heliax_1000yd_knot.jpg" width="198" /></a></div><p style="text-align: left;">In a forthcoming article I will talk about the Skyhawk in depth since I found the antenna design to be quite intriguing. It is well worth a close look. The XM240 I've owned for quite some time, from <a href="https://ve3vn.blogspot.ca/2015/07/for-future-consideration-40-meter-yagi.html">before</a> I moved to this QTH. I bought it when it became available during the planning stage while I continued to live in the city. After the move to this QTH, it has been on a variety of towers:</p><p></p><ul style="text-align: left;"><li><a href="https://ve3vn.blogspot.com/2017/01/topping-trylon.html">Onto the Trylon</a> when it first went up the first winter</li><li>Moved from the Trylon to the <a href="https://ve3vn.blogspot.com/2017/12/topping-150-tower.html">top of the 150' tower</a> when it was built the next year</li><li><a href="https://ve3vn.blogspot.com/2019/09/one-step-back.html">Removed</a> from the big tower and <a href="https://ve3vn.blogspot.com/2019/09/one-step-forward.html">put back</a> on the Trylon</li><li>Now it has moved from the Trylon back to the big tower, but side mounted</li></ul><p>This is all fine, but by this point many readers must be thinking: why? Why keep moving these large yagis from one tower to another? Surely it's better to decide what I want or need, put them up and keep them there. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi6rgKo_AKA467am0HsWKFeG4n-yzx623LT7dKPVBCCpuDFTYgnI53nboWvCzW7ZJM82HzxF_SBc7tLhLNghyphenhyphen6WIx_MACD7vQU_kG6RrzreeyhcQeTcr1Dtps4CYqqBL0aeQMBY-35olEq42xIq7zvEZalh7yLx4SXCx7aFF3fhG3VUcz9GbVRUgimk71QV/s800/skyhawk_from_lr20.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="468" data-original-width="800" height="374" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi6rgKo_AKA467am0HsWKFeG4n-yzx623LT7dKPVBCCpuDFTYgnI53nboWvCzW7ZJM82HzxF_SBc7tLhLNghyphenhyphen6WIx_MACD7vQU_kG6RrzreeyhcQeTcr1Dtps4CYqqBL0aeQMBY-35olEq42xIq7zvEZalh7yLx4SXCx7aFF3fhG3VUcz9GbVRUgimk71QV/w640-h374/skyhawk_from_lr20.jpg" width="640" /></a></div><p></p><p>There is a method to my madness. I am not intimidated by big antennas and towers, and I have the experience (and time) to undertake these frequent changes. I choose where I want an antenna based on the state of station construction and my operating objectives. The latter is primarily contests. For daily operating there is no great need for so many towers and antennas. Of course many non-contesters do it anyway, just because they can and it can be a lot of fun. </p><p>I'll take you through my thinking so you can better understand why I've taken the trouble to do all this work. While you read, keep in mind that my primary operating activity is contests. Several of these points were documented in the <a href="https://ve3vn.blogspot.com/2023/01/2023-exploring-options.html">2023 station plan</a> that I published in January.<br /></p><p><u>Traps</u>: Traps in yagi elements have loss and narrow the SWR bandwidth. I have long yearned to free myself of them but the reality was that I had them and they filled a need. I've reached the point where I can mostly eliminate them. The Explorer 14 was sold last year and the TH7 sold this year. As I explain below, I decided to keep the TH6 to fill an ongoing need.<br /></p><p><u>Solar maximum requires more </u><u>high bands </u><u>agility</u>: 10 and 15 meters conditions are great and they're going to get even better. With only so many hams and hours in a day, it is no surprise to find increased activity on 10 and 15 meters, and less on 20 and below. For the next few years it is valuable to have more antenna options on 10, 15 and 20 meters. For the coming contests there are now 3 antenna choices on those bands, and the ability to split the stacks.<br /></p><p><u>Rapid access to W4, Caribbean, South America and Central American</u>: Several years ago, before building the rotatable side mount, I fixed the TH6 south. It's back but a few feet higher. Skip is shorter when the solar flux climbs and there are more southern US stations available to be worked on the high bands. It isn't a high traffic path so it typically isn't desirable to point the better antennas in that direction. With a click of the mouse, the TH6 provides instant access to the south for DX multipliers and the southeast US. Once the targetted station is worked, another click returns the operator to where they were.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjXffEtwLHaXBAO2wicvIB0xy0hGbNU3ZneifqaAlkgwdpDzLPgnPaaKa0V5YwZ9F1yyxItNZ2tj7STjrdJNLWdnxmktgZfyn2EC2n1Hpc3bVS-jFTUY5sGeyPOBLeTIaAubStXcHQegkHKi2lmis_p-o2MQtxu9BHKzyQjWe9CDYFmg_Fcv1vg28_rDguB/s600/th6_fixed_south_80ft.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="542" data-original-width="600" height="361" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjXffEtwLHaXBAO2wicvIB0xy0hGbNU3ZneifqaAlkgwdpDzLPgnPaaKa0V5YwZ9F1yyxItNZ2tj7STjrdJNLWdnxmktgZfyn2EC2n1Hpc3bVS-jFTUY5sGeyPOBLeTIaAubStXcHQegkHKi2lmis_p-o2MQtxu9BHKzyQjWe9CDYFmg_Fcv1vg28_rDguB/w400-h361/th6_fixed_south_80ft.jpg" width="400" /></a></div><p style="text-align: left;"><u>Prop pitch motors are slow</u>: The upper yagis of the 20, 15 and 10 meter stacks and the 3-element 40 meter yagi are turned by prop pitch rotators. They are poor choices for rapidly working multipliers. It is more profitable to use them for running and long DX openings. I turn them to a direction and leave them there for a long time. The smaller and lower yagis are used for less productive paths, shorter paths (e.g. US) and multiplier hunting.</p><p></p><p>Unfortunately, the changes I've made are not all positive. Trade offs were unavoidable. These are the most notable cons of the new arrangement:</p><ul style="text-align: left;"><li><u>Reduced capability on 40</u>: Pre-sunset and post-sunrise the DX elevation angles tend to be higher than during the night due to D-layer absorption. The XM240 at half the height of the 3-element yagi <a href="https://ve3vn.blogspot.com/2022/11/cq-ww-cw-soasb40.html">often outperforms</a> its big brother at those times. Since the side mount only allows 130° coverage from southeast through west, I may suffer a deficit to, for example, Europe in the late afternoon. It can still be used effectively in the morning towards the Pacific and South America. I plan to replace the XM240 next year with an antenna that has more complete compass coverage and that has no loading coils. I can live with the XM240 for one more year.<br /></li><li><u>Potential interference on 20</u>: With so many yagis there is the ever present risk of destructive interactions. The 3-element 40 meter yagi was expressly designed to avoid <a href="https://ve3vn.blogspot.com/2020/03/40-meter-dilemma-interactions-size.html">pattern degradation of the 15 meter stack</a>. I have not modelled the interaction between the tri-banders and the stacks, however I know the TH6 and Skyhawk won't interact because the TH6 points south and the Skyhawk is to the west of it. Due to the respective heights of all the yagis, I suspect the only significant issue may be on 20 meters with the lower yagi of the stack. Modelling the scenarios will have to wait for inclement winter weather when I'll have more free time.<br /></li></ul><p>I believe the negatives are far outweighed by the positives. At least for my style of operating. The 40 meter issue is short term since I plan to replace the XM240 with a better antenna, hopefully in 2024. Coil loaded elements, like traps, increase loss and decrease SWR bandwidth. Yagis suffer more than single element antenna because they are inherently high Q antennas and the radiation resistance is low.<br /></p><p>The agility I've gained on the high bands is worth the risk of yagi interactions. Pattern degradation depends on where the yagis are pointed so it will occur only some of the time. In any case, I don't require ultimate performance from the tri-band yagis since they will be mostly used for rapid multiplier hunting.</p><p>With this big job out of the way I can focus on several other antenna projects. I'll write about each of them as those projects come to fruition.</p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com0tag:blogger.com,1999:blog-6207999661586171874.post-54117251054333605532023-09-26T21:21:00.000-04:002023-09-26T21:22:55.374-04:00Beverage Lightning Protection<p>Beverage receive antennas are very susceptible to lightning. They are long wires that at close to the ground and grounded at both ends. While direct strikes are not rare, the greater threat is typically secondary strikes (low current lightning branch) and inducted current from a nearby strike. I can personally attest to the lightning risk, when my Beverage system has been struck not once but <a href="https://ve3vn.blogspot.com/2022/06/lightning-strikes-twice.html">twice</a>.</p><p>This summer I removed the head end electronics of my three reversible Beverage antennas, disconnected the feed lines and directly grounded the antenna wires. I rarely operate 160 meters during the warm months since noise is high, activity in the northern hemisphere is low and the radials of the primary 160 meter vertical are removed during the haying season.</p><p>One of my summer projects was to add lightning protection to the Beverage antennas. It isn't difficult and there is ample information available on how to do it. Nevertheless I moved slowly. I wanted to better understand how the protection systems work before ordering parts and making the modifications. I am now better informed though far from being an expert. </p><p>When I was satisfied with what I learned I ordered the parts and made the modifications to the Beverage head ends. After completion I tested them to confirm they still worked as they should and then reinstalled them in the field. The Beverage system is back in operation and ready for the fall and winter season.</p><p>The design I settled on is a melding of the methods I gleaned from W0BTU and <a href="https://www.youtube.com/channel/UCaPW-a8NN5LLLI6jAUxil7w">VE6WZ</a>. Those weren't my sole sources but they were well documented with good explanations. I also read what <a href="https://w8ji.com/beverages.htm">W8JI</a> and ON4UN (<i>Low Band DXing</i>) had to say on the topic and I delved deeper into the circuits and explanations from commercial lightning protection device vendors. Any mistakes or misunderstandings are my own!<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJdEE48hbRhlNpFk3CO7edS7grSk4_J9dfhJRa98SvR_s4q_8_d9gQ7FyfzbSv5NgK-pb3kjy9XreftHTfhmC2Rsy6ndIDj4pCiGnFg09R_9ktYlIYt3RdJ9Z27tcsUQheWsiQhUvimng-mVNjat_9Avg9UAaF9fqwGi5W0PjiptrvaYZ4nlgoxYOTu1At/s370/AS3xx%20schematic.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="166" data-original-width="370" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJdEE48hbRhlNpFk3CO7edS7grSk4_J9dfhJRa98SvR_s4q_8_d9gQ7FyfzbSv5NgK-pb3kjy9XreftHTfhmC2Rsy6ndIDj4pCiGnFg09R_9ktYlIYt3RdJ9Z27tcsUQheWsiQhUvimng-mVNjat_9Avg9UAaF9fqwGi5W0PjiptrvaYZ4nlgoxYOTu1At/s16000/AS3xx%20schematic.JPG" /></a></div><p style="text-align: left;">I believe it will be helpful to first review a well-known circuit for coaxial lightning protection. The circuit above is used in a variety of products made by <a href="https://www.arraysolutions.com/surge-and-rf-protection/as-303u">Array Solutions</a>. I chose it in particular because they are open with their design and their products are used by many hams.</p><p></p><p>Lightning and atmospheric static discharge have both RF and DC components. A blocking capacitor on the ungrounded centre conductor is not effective on its own since the surge has nowhere to go and the potential will build until it exceed the capacitor's breakdown voltage. The capacitor holds the charge at bay, briefly, while other components ground the surge. </p><p>There is no DC component in the RF signals hams work with so an RFC (choke) grounds the DC component of the surge or static buildup while blocking RF. If the DC charge is large enough or increases faster than the charge can be grounded via the RFC, or the RF potential is large, the GDT (gas discharge tube fires (conducts) and it has a short-term ability to conduct kiloamps of charge. The diagram text explains the other components.</p><p>It should be obvious that the choice of capacitor and RFC affects normal operation. The capacitor in particular should have a low reactance and high Q over the operating frequency range suitable to the power rating and maximum SWR. A higher power rating is recommended even with less than legal limit power unless a low SWR is certain.</p><p>A DC surge with a slow rise time and moderate current might be handled entirely by the RFC if it does not overheat and fail from grounding the surge energy. This is desirable since the GDT will fail from repeated firing and conducting high currents, so we want to reduce how often it fires. For maximum protection they should be replaced after several secondary strikes or one primary strike. Since the GDT typically fails open you cannot easily determine that it has failed.<br /></p><p>It should be obvious that the GDT firing voltage should be higher than the maximum voltage for the transmitter power into a 50 Ω load or the higher voltage due to a mismatch. For example, 1000 watts into a 50 Ω load has an RMS voltage of about 225 and a peak voltage of 320. Increase the power and the voltage rises. SWR multiplies the maximum voltage that can be present. Array solutions selection of a 1200 volt GDT is sensible.</p><p>There is more to it than that. The capacitor should be rated to hold off the surge being grounded by the RFC and GDT. How high the voltage grows depends on how quickly and effectively the surge can be grounded. Both the surge and working voltage ratings are relevant. The longer it takes the charge to flow to ground, the longer a high voltage is applied to the capacitor.<br /></p><p>It is not only the current capacity of the RFC and GDT, but also the ESR (equivalent series resistance) of the ground rod's connection to the ground and how quickly the earth charge within the ground rod's "reach" is depleted. An excellent ground connection is no guarantee of the protector's protection during a direct lightning strike. But that's a subject well beyond the scope of this article. </p><p>With measurements, I estimate that the ESR of the 4' copper clad ground rods that I use for my Beverages, in my local soil, is between 100 and 150 Ω, more or less. That doesn't appear to affect Beverage performance but it is not low enough for the best lightning protection. The sooner the GDT fires the faster the charge can be grounded. That motivated my choice of a 75 rather than a 90 volt GDT.<br /></p><p>A receiving antenna has less extreme requirements than transmit antennas because the signal level is very low. A modest amount of signal loss is acceptable and the GDT can be chosen that fires at a much lower voltage. Consider the following open-wire Beverage protection system by <a href="https://web.archive.org/web/20181115070846/http://www.w0btu.com/Beverage_antennas.html">W0BTU</a>.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgLq4ihK5NQzziYVGV6y9imz8KZhu5FgySTc6aXhyFCHwr-Ky1WedutR5amiN6Hub17E93YyGVfrEifnRgY851JE7A1AvLXSCfiHkSuTdk0W2O2uGbRqwPmx9FxugisI0EKacZyIRvKKHpxDinwI6XmpqUP7fm5svcTPquM-GeA1BwJo32N0bUj_eO6NZTu/s800/Beverage_control4436.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="522" data-original-width="800" height="418" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgLq4ihK5NQzziYVGV6y9imz8KZhu5FgySTc6aXhyFCHwr-Ky1WedutR5amiN6Hub17E93YyGVfrEifnRgY851JE7A1AvLXSCfiHkSuTdk0W2O2uGbRqwPmx9FxugisI0EKacZyIRvKKHpxDinwI6XmpqUP7fm5svcTPquM-GeA1BwJo32N0bUj_eO6NZTu/w640-h418/Beverage_control4436.jpg" width="640" /></a></div><p style="text-align: left;">The GDT are 90 volts, the RFC is replaced by a 33 kΩ resistor and the capacitors are ordinary ceramic bypass devices. Resistors are cheaper than RFC and can be effective, for RF and not just DC static and surges. Clearly it is far less expensive to protect receive antennas than transmit antennas. We must protect both conductors of the open-wire line, doubling the component count.</p><p></p><p>The capacitor can have a lower voltage rating commensurate with the GDT firing voltage. Since the frequencies are low -- typically down to 1.8 MHz -- the capacitor value must be high for a low reactance. At 1.8 MHz a 0.1 μF capacitor has a reactance of about 1 Ω, which is negligible in series with a 600 Ω antenna. The reactance is lower at higher frequencies so we size the capacitor for the lowest operating frequency. A smaller high voltage capacitor would also suit, except on the feed line side of the unit where the impedance is typically 50 or 75 Ω.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg2JzyEFYlcHEEO594nN82DAjoMVZ0CyyS2gqJ0Yuriigp71r-OCZgLYLqnZDFQSLhiqbeXVmVqfMHi4fi9IgNb6a9iKcewob2KmaMZIeLg_ApTUf6fBqaP2HR8qRETi4IkClNd5yt6nsiNrhJBlEm6wr0McX4tdae6dp_zITS-PcLfTAeOoB_RBVdoyEfa/s800/bev_e-w_lightning_protection.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="441" data-original-width="800" height="352" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg2JzyEFYlcHEEO594nN82DAjoMVZ0CyyS2gqJ0Yuriigp71r-OCZgLYLqnZDFQSLhiqbeXVmVqfMHi4fi9IgNb6a9iKcewob2KmaMZIeLg_ApTUf6fBqaP2HR8qRETi4IkClNd5yt6nsiNrhJBlEm6wr0McX4tdae6dp_zITS-PcLfTAeOoB_RBVdoyEfa/w640-h352/bev_e-w_lightning_protection.jpg" width="640" /></a></div><p style="text-align: left;">My implementation is modelled on W0BTU's unit. Differences include: </p><p></p><ul style="text-align: left;"><li>75 volt 5 kA Bourns GDT were specified by VE6WZ in his Beverage system and I wanted to keep the voltage as low as possible for maximum protection from even minor induction events. I am confident that Steve made a well informed choice.<br /></li><li>The 33 kΩ resistors that drain charge to protect the GDT are ½ watt rather than 1 watt. It isn't a big change and I had them in stock. If a resistor fails the GDT will fire more often and fail sooner.<br /></li><li>The coupling capacitors are 0.1 μF and 1000 working volts. Notice the size in comparison to the 0.1 μF capacitors on the feed line side of the unit (blue, lower right). The 630 volt devices are much smaller. I could have used the 630 volt capacitors from my stock but opted for the larger capacitors for their higher power dissipation.</li><li>I don't directly protect the relay as W0BTU does. The resistor and GDT on the coax centre conductor offers limited protection from lightning conduction between Beverage head ends via the remote switch; the coax shield is already grounded at the remote switch and has limited GDT protection in the head end via the secondary windings of the transformers. The <a href="https://ve3vn.blogspot.com/2022/10/beverage-repair-and-maintenance-again.html">current iteration</a> of the Beverage remote switch uses SPDT reed relays to ground the coax centre conductors of all but the active Beverage. That in itself is good protection. I have being doing the same for control lines <a href="https://ve3vn.blogspot.com/2022/07/station-automation-design-choices.html">wherever feasible</a>.<br /></li><li>The capacitors are mounted on the PCB but not the GDT and resistor. By direct wiring them to ground I keep the high voltage and high current surges away from sensitive components where the narrow separation of copper pads can offer an alternative and perhaps more enticing path to ground. Stranded interconnect wires allow easy removal of the PCB and connectors from the enclosure for service. </li></ul><p>The above design was used for both the <a href="https://ve3vn.blogspot.com/2020/04/reversing-single-wire-beverage.html">northeast-southwest</a> and <a href="https://ve3vn.blogspot.com/2021/04/east-west-reversible-beverage.html">east-west</a> reversible open wire Beverages. <br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiXSCkkViY0v97x7i0Ur0aWYvNui0cnGTpC1PKmqASMAvjxZyM8WzBKA1XIeyXxUA-Vcr2xfAwtRgapWYCZuLUFl4soKafIjMCo9KmO4jUJEHyQC8meisb0I4HUx55CCcDIO2l3XUrGN7HdImsmI1S9B08DIo4C3Z6UmeOnLNTkVG-dj1XJWXzov9NTAei4/s800/bev_n-s_test_protect.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="572" data-original-width="800" height="458" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiXSCkkViY0v97x7i0Ur0aWYvNui0cnGTpC1PKmqASMAvjxZyM8WzBKA1XIeyXxUA-Vcr2xfAwtRgapWYCZuLUFl4soKafIjMCo9KmO4jUJEHyQC8meisb0I4HUx55CCcDIO2l3XUrGN7HdImsmI1S9B08DIo4C3Z6UmeOnLNTkVG-dj1XJWXzov9NTAei4/w640-h458/bev_n-s_test_protect.jpg" width="640" /></a></div><p style="text-align: left;">The 470 Ω resistor between the Beverage wires was fitted temporarily to test that the added components do not affect normal operation of the unit. Above is a test of the modified <a href="https://ve3vn.blogspot.com/2020/04/reversible-rg6-beverage-antenna.html">north-south RG6 reversible Beverage</a> head end. The SWR curve is not perfect since I used a 51 Ω resistor on the antenna rather than 75 Ω, the analyzer is normalized to 50 Ω and the coax between the analyzer and unit is RG6. This was merely a sanity check that I had made no serious mistakes since all the head end units were in good working order.</p><p></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh3r-JIt8Od-LPxiTw0JARJ82P2M3gZXgvux_hpldXoR6oa_ORUjko2oZfeZoN6ZbJNiD6grmfUL-9jqeLGawepFPgkv6CjHk2oKyFM96KisXJOlWyJrH_d0WiH1KruIoelD6EAtHUwESgrs6QmMZDiYFlAewByFlneVmhIOJIHLfNgPZowmlPCx3yXcD6H/s800/bev_n-s_lightning_protection.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="454" data-original-width="800" height="364" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh3r-JIt8Od-LPxiTw0JARJ82P2M3gZXgvux_hpldXoR6oa_ORUjko2oZfeZoN6ZbJNiD6grmfUL-9jqeLGawepFPgkv6CjHk2oKyFM96KisXJOlWyJrH_d0WiH1KruIoelD6EAtHUwESgrs6QmMZDiYFlAewByFlneVmhIOJIHLfNgPZowmlPCx3yXcD6H/w640-h364/bev_n-s_lightning_protection.jpg" width="640" /></a></div><p style="text-align: left;">Here's a closer look at the reversible RG6 Beverage head end. The antenna port is on the right and the feed line port is on the left. The GDT and resistor pair protect both conductors of the antenna coax. The outer conductor protection is obviously needed. Inner conductor protection is in case of strong coupling between conductors or from the far end via the reflection transformer. I want to avoid a protection path via the fragile transformer windings.<br /></p><p></p><p>I did not protect the reflection transformers. In previous lightning strikes the reflection transformers were unaffected so I didn't feel the urgency. I will probably go ahead and add the protection after the flurry of fall antenna projects come to an end. It isn't a priority.<br /></p><p>The Beverages head ends are back in service -- well, after locating a cold solder joint. I am now ready for the 160 meter season, except...I am in the process of modifying my <a href="https://ve3vn.blogspot.com/2020/11/160-meter-shunt-fed-tower.html">big vertical</a>. For the time being I have only 4 radials installed, which I rolled out earlier than usual to work E51D. I'll have more to say about improvements to the vertical once the work is complete. One of my objectives this year has been to improve my 160 meter signal.</p><p>I also plan to protect the multitude of control lines and rotator cables. Although many are grounded by relays when not energized, others cannot be grounded that way. Unlike RF transmission lines, DC lines cannot be protected by series blocking capacitors. I have not yet settled on a design. </p><p>There are many months to work on it before the arrival of the 2024 lightning season. That is also when I will find out how well the Beverage protection works. My intent is to leave them connected year round.</p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com0tag:blogger.com,1999:blog-6207999661586171874.post-61931169749264080982023-09-20T20:57:00.000-04:002023-09-20T20:57:29.090-04:00Cutting Small Tubes With Hand Tools<p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhYzGBHNog0pgHwdYiIyL5oXad0fF4AaiWgovFG_hE3NFTxaBsm9qgWXPSiwP9-YYmjem4nonY9rzWLo9QuaHgXAAOaJsKdPphBQHr_RhZwPmxImnIzwtf8ARq8zjvKbVj7z-ep4Ar79ZdQKbcTnIC429WHZeWZDxoLA_jeT3qGMPSFvs-k9479Ug6E5Ma_/s600/bandsaw_king_lores.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="600" data-original-width="600" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhYzGBHNog0pgHwdYiIyL5oXad0fF4AaiWgovFG_hE3NFTxaBsm9qgWXPSiwP9-YYmjem4nonY9rzWLo9QuaHgXAAOaJsKdPphBQHr_RhZwPmxImnIzwtf8ARq8zjvKbVj7z-ep4Ar79ZdQKbcTnIC429WHZeWZDxoLA_jeT3qGMPSFvs-k9479Ug6E5Ma_/s320/bandsaw_king_lores.jpg" width="320" /></a></div><p style="text-align: left;">While working on a few antenna projects recently I cut a lot of ⅝", ½" and ⅜" aluminum tubes. This is a subject I touched on briefly in an article on <a href="https://ve3vn.blogspot.com/2019/10/cutting-pipe-square.html">cutting pipe square</a>. Making a straight 90° cut of a round object is not as easy as it might seem. Lucky for us, extreme accuracy is unimportant in the construction of HF yagis. An ugly cut is usually hidden inside the next larger tube, where it is invisible and soon forgotten.</p><p></p><p></p><p style="text-align: left;">The 3 most common ways to cut small tubing:</p><p></p><ol style="text-align: left;"><li>Pipe cutter</li><li>Hacksaw (with guide)</li><li>Band saw</li></ol><p>When I first moved to this QTH with a plan to build many antennas, I considered purchasing a band saw. They're wonderful machines that make clean and reliable cuts with little effort. New ones aren't cheap and used saws come with risks do to their age and maintenance record.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhlJasCK4ZPGzb7JF9GJu0bbabvqrd8ocq2KFIXFdCuYJNtSqB9itiiqvNd5qJCJav-XLLcs_hLTxUZ-idLaSY-_Y9zfhW-Q5DdphuvKxKtNuljBinvjRbcD0RcehWCufVXd9CQE6WCrm5z_LkYgu_rzvbYm3BxCbxfnDhbzmbz0IohvVxUKV39_nQlBPol/s243/mitresaw_nope.png" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="243" data-original-width="238" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhlJasCK4ZPGzb7JF9GJu0bbabvqrd8ocq2KFIXFdCuYJNtSqB9itiiqvNd5qJCJav-XLLcs_hLTxUZ-idLaSY-_Y9zfhW-Q5DdphuvKxKtNuljBinvjRbcD0RcehWCufVXd9CQE6WCrm5z_LkYgu_rzvbYm3BxCbxfnDhbzmbz0IohvVxUKV39_nQlBPol/w196-h200/mitresaw_nope.png" width="196" /></a></div><p style="text-align: left;">Many of us have a table or power saw that might seem suitable, but they are not. The blades are not designed to cut metal and the rotation speed is far too high. Aluminum in particular requires a slow speed saw. If you could get around these obstacles, do you really want aluminum shrapnel flying out of the back or damaging the saw? Those tools are designed to cut wood, not metal. </p><p></p><p>I chose to delay the purchase of a band saw and used hand tools for cutting metal. I never did buy that band saw and now that the construction flurry of the past several years has abated it hardly seemed worth it now. Cutting large pipe, tubes and plates with hand tools takes time and can be tiring. My time as a retiree is not a scarce resource and exercising the arm muscles has benefits. Others would choose differently.</p><p><b>Tool quality</b></p><p>To save yourself a lot of grief, do yourself a favour and buy high quality tools. Do not go by price alone since that is no guarantee of quality. Consider yourself fortunate if you have an acquaintance with metalwork expertise who can point you in the right direction. Otherwise you need to know what to look for in a tool.</p><p>It's time for a story. When I was in my early 20s I took a bicycle making course from a master frame builder. I loved bicycles and cycling and I wanted to learn more. This was back in the days when the best bicycle frames were made of high strength, thin wall steel. There were only a handful of reputable makers of high end steel frame components -- my choice was <a href="https://www.columbus1919.com/en/tube-sets/">Columbus SL</a>.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggnfrFytWCHwF9fZg3IDOk_BI1aGK2JMSYK6FL1wrXnCcytWUwuW45ogzHb6LdUBR4pU3l5JmVDD90BlGuQvPUECiQe1rsbNImDeL7RCik2zGlEANIFDoepliFVwl8nIrsnnJ5CVF-awgMkPh5p2v1W0jxAMQxWAwNscvnk201iVzTfAdsN6VYcZX50wXQ/s640/hacksaw_ct.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="639" data-original-width="640" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggnfrFytWCHwF9fZg3IDOk_BI1aGK2JMSYK6FL1wrXnCcytWUwuW45ogzHb6LdUBR4pU3l5JmVDD90BlGuQvPUECiQe1rsbNImDeL7RCik2zGlEANIFDoepliFVwl8nIrsnnJ5CVF-awgMkPh5p2v1W0jxAMQxWAwNscvnk201iVzTfAdsN6VYcZX50wXQ/w400-h400/hacksaw_ct.jpg" width="400" /></a></div><p style="text-align: left;">The course was held in a community college where they had classrooms equipped with enough hand tools and gas welding equipment for all of us. However the instructor urged us to buy our own high quality hand tools. Of course not everyone did, saving expense by using whatever was in the tool room.</p><p></p><p>When one student ran into difficulty cutting a (very expensive) oval tube, the instructor proceeded to demonstrate the correct technique with the shop-supplied hacksaw. It could not cut in a straight line. The hacksaw frame twisted and the blade warped no matter how much tension was applied to the blade. In an angry outburst he nearly hurled the saw across the room. </p><p>He calmed down and turned the incident into a lesson. He carefully explained the flaws in the tool's design and how it would damage the work. He rooted through the tool room and found one hacksaw that he decided was adequate. He demonstrated the difference. <br /></p><p>It's been many long years and I have not forgotten that lesson. I was careful to buy good tools even when I was loathe to spend the extra money. When you consider the pain you encounter with poor tools there really is no such thing as a cheap tool! Some of my best tools seem to last forever and continue to work well despite their heavy use. One example is my hacksaw, pictured above.</p><p>That is not an expensive tool. However it was pricier than many others. Although the logo is that of a popular Canadian brand, that is only the branding. I don't know the manufacturer. There are others like it to be found if you shop carefully.</p><p>When I bought it I inspected the structure and then performed a few simple tests. Firmly grip the handle with one hand and place your other hand on the back bar. First, try to rotate the back bar. The hacksaw should twist very little and instantly rebound when you release the pressure. If it moves more freely, the backbone or its mechanical bond the with handle and back bar are inadequate. Second, try to pull the back bar towards the handle. It should strongly resist and not behave like an accordion.</p><p>The final test may be difficult to perform in a store. Install a blade and bring it up to a high tension. If you can't achieve that it should be rejected -- the structure twists or accordions, or the tensioner is weak or is uncomfortable for your fingers. Next, try to twist the blade with your fingers. If you have adequate tension you will find it very difficult to twist. Check that the blade is vertical and straight.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh5P22tcn3BcMD_AhllNsVnh7rZDkL-nfVHZx6XEs4Ct7i6deUgzdWjERx8v0kR6kLXJlaLdMCueevxTsN6KWE2d3Xl0y0IgUIzBAu_NcNSv6XzbXwhFoQE4IIuqg2XNq239YVyYIsTy2iFEESze4WiGe_4uQSIIa6ZhSYEueJtq6n4EqBnbpCYzhWwxerL/s640/hacksaw_blade_teeth.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="219" data-original-width="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh5P22tcn3BcMD_AhllNsVnh7rZDkL-nfVHZx6XEs4Ct7i6deUgzdWjERx8v0kR6kLXJlaLdMCueevxTsN6KWE2d3Xl0y0IgUIzBAu_NcNSv6XzbXwhFoQE4IIuqg2XNq239YVyYIsTy2iFEESze4WiGe_4uQSIIa6ZhSYEueJtq6n4EqBnbpCYzhWwxerL/s16000/hacksaw_blade_teeth.jpg" /></a></div><p style="text-align: left;">My hacksaw passes these tests. I've owned it for close to 20 years and it continues to perform well. Longevity isn't easy to test, but it is easy to achieve with a good tool that is not misused or abused. The only maintenance I have to do is to change blades when they wear out.</p><p></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPPbYcVMve67zMbYFjEfGBL30lBSykgieez7VZD_3ITF3qpO6AcL4-riLUR3h2bTHIhxPM3O2paNxHvSEWlCpGRvmS4tnEuEQjkg7JMzYVSya0Pur9pV3z9_vLCDI7ocxZrwG6t-2dWCInPk9w4KNqo0n-9Kb6ADhSiqO98gTQxkNzsYYmBmIemM4vE7zk/s607/hacksaw_cut_0.08in.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="607" data-original-width="400" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPPbYcVMve67zMbYFjEfGBL30lBSykgieez7VZD_3ITF3qpO6AcL4-riLUR3h2bTHIhxPM3O2paNxHvSEWlCpGRvmS4tnEuEQjkg7JMzYVSya0Pur9pV3z9_vLCDI7ocxZrwG6t-2dWCInPk9w4KNqo0n-9Kb6ADhSiqO98gTQxkNzsYYmBmIemM4vE7zk/w132-h200/hacksaw_cut_0.08in.jpg" width="132" /></a></div><p style="text-align: left;">The common hacksaw blade length is 12". Don't buy a smaller hacksaw because you'll find it difficult to cut plate and large pipe. Don't skimp on blade quality. The better blades are well worth the premium price. I stick with 18 teeth/inch for cutting steel and aluminum. A finer blade has little benefit for antenna work, in my experience, although it can help to start the cut without the blade skipping sideways.</p><p></p><p>The width of a hacksaw cut is no narrower than the blade's maximum width. A perfect cut isn't possible so expect it to be a little wider. I measured the cut on the tube slit at right at 0.03", using the above 18 teeth/inch blade. When you cut a 12" tube into two equal pieces and file the edges clean, each will be slightly less than 6". I've never found this to be a problem in antenna work. For finer work, position the hacksaw blade to the outside of the measured cut line.<br /></p><p>I use a flat file to trim the small lip created by the cut. The blade primary removes material but it also pushes some to the side. A round file removes the lip and debris inside the tube. I use a small triangular file to clean the cut edges of tube slits, inside and outside.You want smooth surfaces to avoid cutting yourself when handling the cut tube and to ensure good mechanical and electrical performance when telescoped inside a larger tube.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiDNZAR_VOa3G_DuJwP_hqNOot2eNTXJJEPq4P3Z-h4NLl5u99FkHCGxF7Ba3BeV_HyULXI4dijVL1PqWH3DYXjjk26HyKhI3CFfPxhwrH4KKggXK1AGIcCOhZ1ggQ5eo8etYbjjoDAAJvfDyCAI8vRxSjr2EaJn8rJSxWq_slESd9CfuLXrHXp9Zajbgpc/s717/pipe_cutter.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="717" data-original-width="360" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiDNZAR_VOa3G_DuJwP_hqNOot2eNTXJJEPq4P3Z-h4NLl5u99FkHCGxF7Ba3BeV_HyULXI4dijVL1PqWH3DYXjjk26HyKhI3CFfPxhwrH4KKggXK1AGIcCOhZ1ggQ5eo8etYbjjoDAAJvfDyCAI8vRxSjr2EaJn8rJSxWq_slESd9CfuLXrHXp9Zajbgpc/s320/pipe_cutter.jpg" width="161" /></a></div><p style="text-align: left;">On to the next tool. I have two pipe cutters, one small and one medium size. They are not precision tools. Care is needed to ensure clean, square cuts. This might be surprising to some. After all, you have a blade and wheel in fixed alignment rotating around the tube. What could possibly go wrong? <br /></p><p></p><p>In a picture below you can see several tubes cut with the pipe cutter shown at right. If you look very closely you'll notice that some of the cuts are not 90°. The obliqueness is small but it's there. Again, that isn't important for antenna work. It has to do with tool design and how it's used. Even a good pipe cutter can be mishandled to cut poorly.</p><p>The tool looks simple enough.. A sturdy frame supports a roller and a round blade. The blade is thin and wedge shaped but harder than the metal to be cut. You open the gap to fit the tool over the tube and then pull down the blade until it contacts the tube, while ensuring that the roller is flush to the opposite side of the tube. You spin the tool and periodically draw the blade inward until it pushes through the tube wall.<br /></p><p>In a perfect world this would result in perfect cuts. The world isn't perfect and neither are tools.</p><p>The blade and its body spin on a removable axle (to allow for blade replacement) between the 'C' arms of the tool body. The imperfect fit for both allows for play. The worse the tool or due to long service the greater the amount of play. My pipe cutters are of no better than moderate quality. Spending more didn't seem worthwhile since the cuts are often hidden and aluminum alloys are soft compared to other metals. The blades can last a long time when only used for cutting aluminum tubes.</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_nH37C4-Xrs9eqckNSELhqyl_GBX7-aupVDXBrmCmKltx5uselinCWJsiacLGCBTO3Pln0aaP92rVecX_azhq74DznV87HuaaLg2isW22qtJJEdKvb6mO5_LgHPSyjY4SEE3g8YsSZ8JdRl6knNLM3EHsedmPcYzxtvN3oTs7Y6B2SZEtRnv8oN5kYx65/s826/tube_cutter_and_tubes.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="826" data-original-width="800" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_nH37C4-Xrs9eqckNSELhqyl_GBX7-aupVDXBrmCmKltx5uselinCWJsiacLGCBTO3Pln0aaP92rVecX_azhq74DznV87HuaaLg2isW22qtJJEdKvb6mO5_LgHPSyjY4SEE3g8YsSZ8JdRl6knNLM3EHsedmPcYzxtvN3oTs7Y6B2SZEtRnv8oN5kYx65/w310-h320/tube_cutter_and_tubes.jpg" width="310" /></a></div><p style="text-align: left;">Aggressive force on the blade will cause the blade to tilt at an angle. It may track in a circular pit or it may wander or spiral. I've found it very easy to trace a spiral when cutting PVC pipe since the soft plastic "grabs" the tilted blade. It's important to start the cut with light pressure no matter the material.</p><p></p><p>Despite being careful the cut might not be square. Can you tell from the picture? Expand it to full size and the tubes with a bad cut will be easier to identify. </p><p>The other thing you should notice is the profile of the raw cut of the tube posed in the pipe cutter. It is far was than what you get with a hacksaw or band saw. While it may be easier to cut a tube with a pipe cutter, there is more filing to be done afterward.</p><p>First, the cut is not vertical. It has the same profile as the wedge shaped round blade. A flat file on the open end of the tube (for both tube halves) is needed to remove the large angled projection.</p><p>Second, the cut is not as clean as a hacksaw because the pipe cutter does not remove material. The material pushed aside by the blade piles up to form a substantial lip. It is high on the outside of the tube and shallow on the inside. Both lips should be filed flat so that the end of the tube is corrected to its original diameter. You can see the filing marks on the set of tubes above. Don't skip this step or you may have difficulty telescoping it into the next size larger tube, and even if you do the mechanical and electrical performance will suffer. </p><p>A quick sweep of a round file is usually enough to clear the lip on the inside of the tube. For the outside lip I use a flat file while rotating the tube. Be careful not to file into the tube surface while you abrade the lip.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMUH9RB4OeO21W0NUU4o_3bkxhMTf7u22oQ_rwaoJIhUbftIZTH_3m3ounnqvm3DGkMATc7ziVvyaPVBL4T7d-sQVkwp3Jus6OolC-JZdO_slhe1AGLbV4uWD-SSkY8Viai2yn5YHuy1ATsBBcb-b-D84mEX4gPSmJkZovcv0CGy4QPaaySFGp7B39tqdO/s275/butter_knife.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="91" data-original-width="275" height="91" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMUH9RB4OeO21W0NUU4o_3bkxhMTf7u22oQ_rwaoJIhUbftIZTH_3m3ounnqvm3DGkMATc7ziVvyaPVBL4T7d-sQVkwp3Jus6OolC-JZdO_slhe1AGLbV4uWD-SSkY8Viai2yn5YHuy1ATsBBcb-b-D84mEX4gPSmJkZovcv0CGy4QPaaySFGp7B39tqdO/s1600/butter_knife.jpg" width="275" /></a></div><p style="text-align: left;">A pipe cutter works like a butter knife. It pushes the soft butter aside rather than removing it, or splitting it like the ways a chef's knife cuts pliant vegetables. Metal tubes are too rigid for cutting with a knife.<br /></p><p></p><p><b>Does it matter?</b></p><p>As I alluded to earlier, pretty cuts are rarely important for antenna work. Once it's in the air no one will notice. You might think that it'll bother you but it won't. You'll soon forget, and you'll forget even sooner the more antennas you build.</p><p>What matters is safety and performance. Improperly finished cuts will draw blood when you handle the material. Even for the clean cuts of a band saw I take a few moments to remove imperfections and the small ridges at the inner and outer tube edges. For mechanical and electrical performance we want maximum surface contact where tubes overlap. The ridge formed by a pipe cutter prevents that. For those of us in cold climates, an exposed ridge at the element tip can increase ice buildup and delay sloughing off when the sun comes out.</p><p>So, yes, it matters. It's worth the small investment of time and effort to clean the imperfect cuts of a pipe cutter or hacksaw. Or you can invest in a band saw. Then you will spend the time that you saved to keep it in good working order and spend more money on those long flexible blades. In my opinion, buying and learning to use good quality hand tools is the right choice for most hams. If you're the rare exception, by all means invest in a band saw.<br /></p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com1tag:blogger.com,1999:blog-6207999661586171874.post-89525247699910576432023-09-14T22:15:00.001-04:002023-09-14T22:16:07.948-04:00New Operating Desk<p>Widely spaced blog articles are due to me being very busy and a lot of partially complete projects that are not ready to become blog material. I was sitting in my easy chair one evening, utterly fatigued, and looked around the shack. I realized that I had not yet mentioned the new operating desk that I put into service in late August. I'll remedy that oversight now.</p><p>The previous iteration of operating desk did not work out well. It was the product of ideas not fully worked out, my horrible carpentry skills and a few unfortunate design choices. I <a href="https://ve3vn.blogspot.com/2023/08/preparing-for-fall-antenna-work.html">ripped it out of the shack</a> and made another attempt. What I learned from my mistakes led me to an improved design. Now that it's been in use for a few weeks it is worth a look.</p><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhE_3B-clJpLJdJKMlV2sKUnyUO7vGN6WUxrqlBmbrsZYUYSsmiS2tft3ixqEhUz73MiX3xwCOStL-TpdpyCybgdZLReBO1jEcw0_cFz3RdXUJEY5VMLqv8YYts0-R5szDMlO8v82IsBpoxq51I-EInMHTYFfxcmZ5ZEUFgWkfo1OrXxBh2JVOjYFTLWaOb/s800/new_desk.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="366" data-original-width="800" height="292" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhE_3B-clJpLJdJKMlV2sKUnyUO7vGN6WUxrqlBmbrsZYUYSsmiS2tft3ixqEhUz73MiX3xwCOStL-TpdpyCybgdZLReBO1jEcw0_cFz3RdXUJEY5VMLqv8YYts0-R5szDMlO8v82IsBpoxq51I-EInMHTYFfxcmZ5ZEUFgWkfo1OrXxBh2JVOjYFTLWaOb/w640-h292/new_desk.jpg" width="640" /></a></div><p style="text-align: left;">First, I will state the obvious: it is not complete. I continue to work on placement of the equipment and cable routing. The second (right) radio is installed but not connected. Desk setup is improving, slowly, and it will be a keeper for a year or two at least. My objectives for the design include:</p><p></p><ul style="text-align: left;"><li>Ergonomic improvements for SO2R contests</li><li>Rapid rearrangement for two operating positions in multi-op contests</li><li>Keeping the mess of cables out of sight, especially those for the station automation system</li><li>Convenient access to the back panels and cables for service and configuration changes</li><li>Improved appearance</li><li>Space to place infrequently or never touched equipment out of sight</li><li>Lots of legroom without the risk of knees and shins bumping into the desk structure<br /></li><li>Support heavy equipment, especially amplifiers <br /></li></ul><p>I was unhappy with reasonably priced commercial products that met my objectives. Monitoring the local used markets found many inexpensive office desks, but all had at least one fatal flaw. Maybe one would have appeared had I waited but with contest season approaching I had to act.</p><p>A friend with a truck brought a 4' × 8' × ¾" sheet of fir plywood to his workshop where we ripped it to a 30" depth and routed the edges. The remaining 8' x 18" of the sheet was set aside for shelves that will be built later (more on this below). <br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiG6e7QdytKwxgT3qzeou3pKt96W7z8u_sUcyJhsXy6Vlwl6Fo5ixdtiPmEjfy5okpTs745G0VW2T8XJdL5w-kx22OapppudX3Wx-hyRGHxemMkuh9xjV0K7oqIMVz1rU2Rb0GryT2KYrbUy8SXzVpTRdeeH8b1-bXMI1LHalRkp5KWB9QSva4y4K_YMNoA/s800/new_operating_position.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="491" data-original-width="800" height="392" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiG6e7QdytKwxgT3qzeou3pKt96W7z8u_sUcyJhsXy6Vlwl6Fo5ixdtiPmEjfy5okpTs745G0VW2T8XJdL5w-kx22OapppudX3Wx-hyRGHxemMkuh9xjV0K7oqIMVz1rU2Rb0GryT2KYrbUy8SXzVpTRdeeH8b1-bXMI1LHalRkp5KWB9QSva4y4K_YMNoA/w640-h392/new_operating_position.jpg" width="640" /></a></div><p style="text-align: left;">He delivered the plywood to my workshop where I stained it and put on several coats of polyurethane. I kept most of the <a href="https://ve3vn.blogspot.com/2022/12/anniversary-and-peek-ahead.html">frame of the previous desk</a>, discarding the desktop and beefing up the structure so that it is very stable and capable of supporting a heavy load. I put them together and positioned the new desk next to my (non-ham) desk to form an L. I was careful to make the desktops the same height.</p><p></p><p> My old <a href="https://ve3vn.blogspot.com/2014/03/moving-into-shack.html">1980s operating desk</a>, which I revived almost 10 years ago, has the same fir plywood top but it was not suitable. Too much space was taken by a set of drawers and the vertical side supports, and it is a foot shorter than the original 8' sheet size. Although perfectly good for SO2R, it is inadequate for two operators. <br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj5A33yRfeXwaHzuy9eZNtnql7BZH45MT2sW4P3pN7sjD5tlOpkR8MzcLWy6PTriKwHrpt19BgfO_MA2ArBjyGKilLQ-1uhGyTHza_TmDMzDWnNrq_UaELy6xWKFArHZ9OFZZXavP2m9eZnai9dd65ZQakkl7ostdzsPbb70LusLAkGhDfFvJs3tmNM_BJP/s600/new_desk_frame.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="567" data-original-width="600" height="378" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj5A33yRfeXwaHzuy9eZNtnql7BZH45MT2sW4P3pN7sjD5tlOpkR8MzcLWy6PTriKwHrpt19BgfO_MA2ArBjyGKilLQ-1uhGyTHza_TmDMzDWnNrq_UaELy6xWKFArHZ9OFZZXavP2m9eZnai9dd65ZQakkl7ostdzsPbb70LusLAkGhDfFvJs3tmNM_BJP/w400-h378/new_desk_frame.jpg" width="400" /></a></div><p style="text-align: left;">The desktop height must be identical to that of the adjacent desk. I got it right but it still wasn't good enough. At 8', the desk is so long there is a small sag even with a stiff frame. But the level match is very close, less than ¼" of sag at the interior corner. The keyboard wobbles a bit when it lies across the boundary, which is where it will be for SO2R with two keyboards. The pointy right front edge of the left desktop is exposed and can catch unwary fingers.</p><p></p><p>The horizontal lumber of the frame is rearward to take the weight of the equipment while staying beyond reach of the operator's knees. Addressing the sag with a forward beam isn't possible. However a mid-span vertical support can work. I will experiment to find one that removes the sag and doesn't limit the excellent legroom.</p><p>The operating desk was designed to be functional and not pretty. The frame is the lumber equivalent of "plumber's delight" yagi construction. Metal stiffening plates are placed where they are most effective and the projecting screws are out of the way of operator's legs and feet. Some are visible when you enter the shack but I don't worry about that. Power bars are mounted to the back of the frame's rear beam.<br /></p><p></p><p style="text-align: left;">The lower equipment shelves support power supplies and the station automation hardware. Other "low touch" equipment will be added later. Eventually the BPF (band pass filters) will move below the desk since band switching is automatic. The station automation hardware (<a href="https://ve3vn.blogspot.com/2023/03/automating-va6am-6-band-bpf.html">pix</a>) is in the back corner close to the floor opening for the cables. The computer is at the back corner of the desktop just above it. That choice keeps the multitude of Cat5 control cables from snaking across the floor or having to be dressed along the underside of the desk. You can see excess blue plenum cables hanging from a hook. </p><p></p><p>I can hardly wait for a full wireless control system so I can dispense with control cables entirely. The same aspiration applies to transceivers; I want all communication between rigs and computers to be wireless. We're getting closer but we're not there yet. There are so many cables that a tangled mess is difficult to avoid no matter how careful you are. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEia2PSnq-qEzm-4H2VwBWcV940N1mVJ8qkRKsFxbzWkQGsY9aQHTXOnTfdcv-VIJpLEgxlLgRecN9IvUr9nwm9sruxw3tG-oKHp6BkdRCZwh9YStveSSWSaDiPeQByKX9gfFO8TdecXspQHOd_swBxz_vVExyowlKecfwBoJBsfAZ9uYsVFWbfQq509snjL/s515/new_desk_rear_access2.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="515" data-original-width="400" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEia2PSnq-qEzm-4H2VwBWcV940N1mVJ8qkRKsFxbzWkQGsY9aQHTXOnTfdcv-VIJpLEgxlLgRecN9IvUr9nwm9sruxw3tG-oKHp6BkdRCZwh9YStveSSWSaDiPeQByKX9gfFO8TdecXspQHOd_swBxz_vVExyowlKecfwBoJBsfAZ9uYsVFWbfQq509snjL/s320/new_desk_rear_access2.jpg" width="249" /></a></div><p></p><p>I kept a gap between the desk and wall to ease service. No more crawling under (or over) the desk to access equipment rear panels and cables. The aesthetics are not great, but at 14" (35 cm) the appearance is acceptable. That may seem too narrow unless you've met me in person; I am exceptionally slim (skinny). Keeping the space narrow may dissuade guest ops from the temptation to venture where they probably should not.<br /></p><p>In the picture at the top of the article you can see a variety of rotator controllers. One recent change was to replace the old Ham-M controller with a newer Hy-Gain model. They frequently appear at flea markets for a reasonable price after the accompanying rotator dies. Two of them make a convenient support for the computer monitor. I may need more (there's another on the far right of the desk) when I modernize the home brew breadboard prop pitch controller sitting on top of the FTdx5000. Visitors are always startled to see that monstrosity, yet it continues to work very well.<br /></p><p>Eventually I will use the leftover plywood to make a prettier corner shelving unit to give the monitor a proper support and to avoid direct stacking of equipment. Amplifiers are dangerous to stack because they are heavy -- the Drake L7 is an exception because the power supply is in a separate enclosure. The extra shelves will wait until I replace the FTdx5000 with a modern rig since it is quite large and won't fit the shelf design.</p><p>The walls of the shack are bare. Not only do I not apply for awards, I have never put contest plaques on the wall. For that matter, my framed university degrees have also never been hung on a wall. The shack walls are more bare than before because I removed a bookcase to make room for the longer desk. Maybe this is an opportunity to dust off the plaques and cover the empty walls. Maybe.</p><p>Since I'm pretty happy with new desk I will continue with station setup and get it ready for the fall DX and contest season. I will tinker with it this winter as time allows. Right now I have a long list of higher priority outdoor projects to complete.<br /></p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com0tag:blogger.com,1999:blog-6207999661586171874.post-50513882941153991762023-09-06T21:06:00.000-04:002023-09-06T21:06:48.022-04:00Singing Isn't Just About the Element<p>Many owners of HF yagis are familiar with the "singing" phenomenon. When the wind blows the elements vibrate. Not always, since it depends on wind speed and direction and element design. It is an interesting sight (or sound) but often not healthy for the antenna. That is, we want to stop it from happening.<br /></p><p><a href="http://www.worldscientificnews.com/wp-content/uploads/2017/07/WSN-812-2017-121-131.pdf">Aluminum can fatigue and fail</a> at well below its yield strength when stress cycled enough times. There are many examples of yagi elements breaking and the tips falling to the ground. This is dangerous and can be expensive to repair. Rebuild the yagi with the identical replacement parts and failure is likely to recur. Some brands and antennas are notorious for singing-induced fatigue failures. Here is one example:</p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgeFVWTlgUwsOxVVtD2FfsaPIFHD2Zl0O3QKi92RJjs_Cge18dklnaV5ySu44NXFwshO8cqWlHDXtVb_ublOj8pxbZ098mbfNQpBCtlKSDWA_SmlI6PiXlsssCTEtvgRUStMEWzQ6cx4lHnDE4_Xps88RuEg9RkVwlaLViGNGgFM1LPm_gagRY0zNM6dumy/s640/broken_elements.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="345" data-original-width="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgeFVWTlgUwsOxVVtD2FfsaPIFHD2Zl0O3QKi92RJjs_Cge18dklnaV5ySu44NXFwshO8cqWlHDXtVb_ublOj8pxbZ098mbfNQpBCtlKSDWA_SmlI6PiXlsssCTEtvgRUStMEWzQ6cx4lHnDE4_Xps88RuEg9RkVwlaLViGNGgFM1LPm_gagRY0zNM6dumy/s16000/broken_elements.jpg" /></a></div><p style="text-align: left;">The tower and antennas have been derelict for several years. The ham is a silent key and before that was unable to deal with the problem. Elements broke off one by one, leaving the denuded antenna seen above. Someone gathered the broken elements and leaned them against the tower. We found another sticking in the ground like a forgotten spear. Luckily the tower is located in a rarely used field so no one was injured. The tower is tentatively on my list for removal this fall.<br /></p><p></p><p>I know many hams dealing with these issues. Large yagis with widely spaced elements may have to be lowered or carefully manipulated on the tower to access and repair broken elements. Some hams take the trouble to redesign the elements, with varying degrees of success. Haphazard changes might change the singing but not eliminate it.<br /></p><p>Yagis that are prone to element breakage are typically the ones that "sing" in the wind. You can often hear the thrumming from the ground. The sound is louder when you're on the tower near the antenna. When the pitch is too low to hear you can still see the vibration. It may not happen at all in a very strong wind, but in those cases you are more likely to be concerned with survival of the antenna and tower.<br /></p><p>Why do antenna sing? When they do, how serious a problem is it and what can be done about it? These are interesting and important questions whether you buy or build yagis. I've found too many hams that simply shrug their shoulders and say that's just how it is. Others are convinced that there is <i>one true method</i> to defeat singing and they apply that to every yagi they own. </p><p>Fatalism and certainty are nothing more than excuses to avoid understanding the issue. This is an opportunity to learn, and if you read this blog with any regularity you will know that, to me, learning is one of the greatest benefits of our hobby. We don't have to be structural engineers to gain an insight into the why of singing and what, if anything, we ought to do about it. I like to keep yagi elements up in the air and I believe that you want the same thing.</p><p>Singing is not an arcane branch of engineering. It is very well understood in the profession. Despite owning my first yagi in 1975, I had little understanding of the phenomenon until relatively recently. I would venture to say that my ignorance is typical of most hams. With the wonders of the internet at our fingertips there is no reason to remain ignorant. It is easy to learn the fundamentals with only a modest effort. Readers who are structural engineers may cringe a little at what follows, but please humour those of us who lack the background.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEifNAWQGZo0pCr6BHSGg8-O4ptvio3-loCEMz8e3tA5lolzMpFH7HhQixfh1YjNnwb26PmPIF4Jy8pAwZ3BsJNWx515-XXZmeIKUC9a44DlEMsWAV9A23vyuf4_XIcEqKWjCpdB2-dc6Yi0OoRGuVW6tBDfUpfgfn1zZdNn71Z486Lql7aLPUyP5Uj4o5Ft/s600/flow_around_cylinder.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="328" data-original-width="600" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEifNAWQGZo0pCr6BHSGg8-O4ptvio3-loCEMz8e3tA5lolzMpFH7HhQixfh1YjNnwb26PmPIF4Jy8pAwZ3BsJNWx515-XXZmeIKUC9a44DlEMsWAV9A23vyuf4_XIcEqKWjCpdB2-dc6Yi0OoRGuVW6tBDfUpfgfn1zZdNn71Z486Lql7aLPUyP5Uj4o5Ft/s16000/flow_around_cylinder.jpg" /></a></div><p style="text-align: left;">[Diagram credit unknown] When a fluid like air encounters a solid object it will flow around it. The crowding of fluid at the front and sides of the object increases the pressure, and in the lee of the object there is a low pressure region. Purposely shaped objects like wings use this effect to generate lift, while the high and low pressure regions due to hurricane force winds can lift the roof off a building.</p><p></p><p>There is a critical fluid velocity where the flow changes from laminar to vortex generation, and finally to turbulence. Vortexes form on the lee side of the object, with the low pressure regions cycling between the upper and lower boundaries of the object. This is know as <a href="https://en.wikipedia.org/wiki/Vortex_shedding">vortex shedding</a>. Objects with freedom of movement will move toward the low pressure regions. As the low pressure region moves back and forth the object moves back and forth. If that frequency is close to the structure's resonant frequency it can oscillate quite vigourously.<br /></p><p>For cylindrical objects like antenna elements there is a <a href="https://en.wikipedia.org/wiki/Vortex-induced_vibration">formula to calculate the frequency</a>. Of course it's never this simple, but for our purposes it is perfectly adequate. One complication among many is the incident angle of the wind. I won't discuss this and other complications in any depth.<br /></p><p style="text-align: center;"><span style="font-family: courier;">F = 0.22 (V / D)</span></p><p>V is the fluid velocity and D is the cylinder's diameter in the same units. For example, if V is expressed as m/s (meters per second) then D <i>must </i>be expressed in meters.</p><p>Let's try an example. Please note that in the following discussion I will liberally round quantities. One significant figure is enough to understand the basics.<br /></p><p>For a 3 m/s light breeze (about 11 kph or 7 mph) impinging on a ½" (1.3 cm) diameter element tube, F is 55 Hz. The frequency is proportional to wind velocity and inversely proportional to element diameter. Thus for a 1" diameter tube in a 6 m/s wind the frequency is identical. </p><p>It is not a given that the tube will vibrate at this frequency since only select vortex frequency ranges will excite the element. The most common is the (mechanical) fundamental resonant frequency. At other frequencies the element will move but not oscillate; yagi elements wiggling when the wind blows is normal and is not to be confused with singing. </p><p>If any tube or tube combination in the tapered element is resonant it can shake the entire element. The tip may vibrate most vigourously because it is smallest tube and unrestrained at one end. A stronger wind on a thin element tube may be at an audible frequency
that you hear on the ground. This is what we know (and fear) as singing.</p><p>It should be evident that singing depends on wind speed and direction. Too slow or too fast and the oscillation will be mild because the element's mechanical resonance is not excited. Also, a wind direction well off from normal to the elements is less able to excite resonances.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi25OI91mAdwM2x3TpSNuBmTb-GgbhfB9XqVIvPSz5X8_IysCwx4r1f3b4xGTRIWCogO3Kehk32bTLj_C6KYBrXG16ujVoahl7P3lT3JeCX7UwCMsYpeutJ3qmPhqO1mXEiBq5CIZ0yAlkFajlDC13uLsnI9VxEZidVU4ZFwMQSdQU-MNyl-6LHFNYjj69v/s640/roped_elements_ancient.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="404" data-original-width="640" height="253" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi25OI91mAdwM2x3TpSNuBmTb-GgbhfB9XqVIvPSz5X8_IysCwx4r1f3b4xGTRIWCogO3Kehk32bTLj_C6KYBrXG16ujVoahl7P3lT3JeCX7UwCMsYpeutJ3qmPhqO1mXEiBq5CIZ0yAlkFajlDC13uLsnI9VxEZidVU4ZFwMQSdQU-MNyl-6LHFNYjj69v/w400-h253/roped_elements_ancient.jpg" width="400" /></a></div><p style="text-align: left;">There are several approaches to mitigate singing:</p><p></p><ul style="text-align: left;"><li><u>Mass</u>: A heavier tube with more inertia is more difficult to excite into oscillation. Greater wall thickness or tube overlap is often all it takes to prevent singing. Very thin wall tubes used in some antennas are more prone to singing.</li><li><u>Damping</u>: Per the <i>ARRL Antenna Book</i> (22nd ed., 25.2.3): "Metal antenna elements have high mechanical Q, resulting in a tendency to vibrate in the wind." Just like in an RF network, resistance lowers the Q and therefore the oscillation potential by dissipating energy. The most common method is to insert rope into the element or just the element tip. Another is to run a piping helix around the tube surface. This is uncommon on antenna elements but I've seen it used to good effect to damp oscillations on Phyllistran synthetic guys.</li><li><u>Texture</u>: Although impractical for hams antennas, the surface of the tubes can be sculpted with patterns that reduce vortex formation and their amplitude.</li><li><u>Turn the antenna</u>: A yagi is typically pointed in the direction of stations you want to work. But when you are not in the shack the singing can be reduced by parking the yagi normal to the prevailing or current wind direction. For example, turn the antenna north or south for prevailing westerlies.</li></ul><p>I won't delve into the finer points of mechanical mitigation measures except to note a few items that I've learned from experience and listening to those with greater knowledge. First, don't use excessively thin wall tubes. It is used in many antennas because aluminum is expensive and manufacturers know that keeping prices low increases sales. Stay at or above the typical 0.058" wall of aerospace high strength tubes, and overlap tubes more than the 3" minimum to further increase mass and strength. Second, beware product instructions that tell you to rope the elements. This is very close to an admission that there is a deficiency in the mechanical design.</p><p>I have watched hams thread rope through under-engineered full size 40 meter yagi elements and I've seen roped element tips fall to the ground. Damping from an internal rope may be insufficient to keep singing in check. Vibrating yagis can also <a href="https://ve3vn.blogspot.com/2017/10/bad-vibrations.html">cause fasteners to loosen</a> or fail, and that can prove disastrous even without tube breakage. My TH6 elements are not roped and the non-trapped 15 meter elements
sing; those of the TH7 were roped yet they also sang.<br /></p><p>Singing isn't always straight forward to resolve, whether by treating the cause (design) or the symptom with rope. Without a comprehensive mechanical model and simulation software we are too often left guessing. When one mitigation method fails should we blindly substitute, say, a different or longer rope, or should we try something completely different?<br /></p><p>We may be going about it completely wrong. For example, mistaking the location of the symptom as the cause of the singing. Consider the following two yagis in my station. These are the upper and lower 5-element yagis of the 20 meter stack. We are looking toward the back of both antennas.<br /></p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhDe4IFIg-x5FblXpE0QQ4OVXks5POO_c39ZNLdVqBKoihUE4wweZJFfIc385RZ48OEv4rNQrqwWCHeOn7UCZoZ-b615CTRYFOw6ksCd01z1Q44lVBQbJUYsGwd2FueyeIN5Mu8B37wZhDStvIII8fyqp9RStvT1DGSelzl1gn0wf56CvZr2DK4iwjHK8Fk/s800/upper_20m_yagi.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="350" data-original-width="800" height="280" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhDe4IFIg-x5FblXpE0QQ4OVXks5POO_c39ZNLdVqBKoihUE4wweZJFfIc385RZ48OEv4rNQrqwWCHeOn7UCZoZ-b615CTRYFOw6ksCd01z1Q44lVBQbJUYsGwd2FueyeIN5Mu8B37wZhDStvIII8fyqp9RStvT1DGSelzl1gn0wf56CvZr2DK4iwjHK8Fk/w640-h280/upper_20m_yagi.jpg" width="640" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEin4NpStiUQr_2OKi7RsPiNUBjmMFycJbMpgzMJJCDSvRKwWcdbhU4jIRXY2u_c9gwox5QGXs1i1BjPqNdnn0MovN2nrHfKFnzPzqi0-xR7dnOPgAwz_qxL0OkTVS3xMrQaxOg5pSZjdZUxFiiIfxqRXiTOKrhg-K9_vmZoNZO3f2VxuPbGYJde9lltgpBv/s800/lower_20m_yagi.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="429" data-original-width="800" height="344" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEin4NpStiUQr_2OKi7RsPiNUBjmMFycJbMpgzMJJCDSvRKwWcdbhU4jIRXY2u_c9gwox5QGXs1i1BjPqNdnn0MovN2nrHfKFnzPzqi0-xR7dnOPgAwz_qxL0OkTVS3xMrQaxOg5pSZjdZUxFiiIfxqRXiTOKrhg-K9_vmZoNZO3f2VxuPbGYJde9lltgpBv/w640-h344/lower_20m_yagi.jpg" width="640" /></a></div><p style="text-align: left;">The construction, size and placement of the elements of the stacked yagis are identical. It may surprise you to learn that one yagi sings and the other does not. I know that I was surprised. Clearly there must be a difference. However we can eliminate a difference in the directions they are pointing since the disparate behaviour remains when the direction is the same (northeast, since the lower yagi is fixed).</p><p style="text-align: left;">The lower side-mounted yagi occasionally sings at moderate wind speeds. It isn't always noticable from the ground and I haven't carefully noted the wind speed and direction when it occurs. Typical for this latitude the prevailing winds are west to southwest, and that is approximately normal to the elements when they sing.</p><p style="text-align: left;">If not the elements themselves, what is the cause of the singing. I believe the answer lies with the frequency of the singing and how the entire antenna behaves. The audio frequency is low, below what a human can hear. The singing is not a sine wave so it may be the weaker harmonics that are heard. But when the singing is bad, <i>all </i>the elements shake and so do the boom and boom truss. That's unusual in my experience.<br /></p><p style="text-align: left;">It is instructive to return to the above equation for vortex induced vibration. A low frequency implies a larger cylinder than is present in the elements, the largest being the 1" × 0.120" centre tube. The boom is the only large cylinder in the antenna and it is approximately the same for both antennas: 3". The equation for the same 3 m/s breeze gives a frequency of 8 Hz. That is in the range of what I observe. I didn't note whether the wind was from the northwest or southeast, which are normal to the boom.</p><p style="text-align: left;">Why only the lower yagi? I think the answer is that the <a href="https://ve3vn.blogspot.com/2018/09/challenges-of-long-boom-yagis.html">booms are constructed differently</a> despite having the same diameter. The tubes comprising the boom of the lower yagi have a wall thickness of 1/16" other than the thicker 10' long pipe at the centre of the boom. The <a href="https://ve3vn.blogspot.com/2019/09/weighing-yagis.html">weight difference</a> of the two booms is substantial. As for elements, the mass of the boom seems to make all the difference.<br /></p><p></p><p>Compared to the elements, yagi booms oscillate at lower frequencies and boom truss cables at higher frequencies. Unlike a singing element, when the boom sings (oscillates) all the elements shake. That appears to be what is happening in this case.</p><p>The solution is simple: replace the boom. I probably have what's needed in my stock of pipes to do that. If not, I can probably find more surplus. It isn't urgent. Watching the entire yagi vibrate is worrisome but it is not an emergency. It happens only occasionally when the wind direction and speed are just right. Maybe next year.</p><p>Singing is an example of structural resonance where the oscillation frequency is usually in the audible range. The 20 meter yagi is singing but the fundamental frequency is not audible. I can't hear it from the ground. A low resonant frequency is common to large structures like houses, bridges, skyscrapers and towers. </p><p>Perhaps the best known example of undamped large structure oscillation is the <a href="https://en.wikipedia.org/wiki/Tacoma_Narrows_Bridge_(1940)">Tacoma Narrows Bridge</a>. Large structure oscillations are more difficult to analyze and defeat because there are many structural elements whose behaviours can be both independent and synergistic. Even so, as with yagis, there are a variety of effective mitigation methods in the engineer's toolkit.<br /></p><p>Years ago I made use of structural oscillations excited by footsteps, wind and various mechanical impulses to sense and measure activity in buildings. It was interesting work. The oscillations were damped by the structure but lasted long enough to glean useful data. Although only minimally relevant to singing yagi, or suspension bridges, the physical principles are similar.</p>Ron Schwartzhttp://www.blogger.com/profile/14421847003357507798noreply@blogger.com0