Early End to Contest Season

Maintenance. There's a word to strike terror into the heart of any ham. Especially when it's needed at exactly the wrong time: the middle of a brutal winter; during a badly needed DXpedition; or, a favourite contest. I now have enough maintenance to do that my contest season is pretty well over.

There are two issues that have cropped up, one that can be managed and one that cannot. The first is the TH6 tri-band yagi on the 150' tower. After repairing intermittency due to a fastener that came loose a more difficult problem appeared. It is more subtle, and also intermittent.

The TH6 has 8 traps: 4 on the driven element and 2 each on the outermost parasitic elements. The aluminum tabs that connect the trap shell (capacitor) to the element are prone to fatigue failures. All it takes is time, although that time is usually (and thankfully) many years. My antenna is old. When I refurbished it in late 2017 I paid particular attention to the traps. I could see that a few of them needed extra attention. Since my time was limited due to the oncoming winter weather I only dealt with the worst of them.

I wasn't unduly worried since I planned to bring the antenna down last summer. The traps only needed to survive 6 to 8 months. As matters transpired I was so far behind schedule that I left it up for another season. Now the antennas had to survive 20 months. It didn't.

Periodic increases in SWR and pattern distortion told the tale. Diagnosis with an antenna analyzer suggested that a trap on the outermost director was intermittent. The sign was that resonance shifted downward well below the band, in effect being pulled lower by the reflector when the suspect director trap was disconnected. I won't know for sure until it comes down.

It works most of the time (95%) so I have to hope it does work when I need it. When it doesn't I lose my best antenna on 20 meters. Fortunately I have two others: one fixed on Europe and a rotatable TH7 at 21 meters.

The second problem is more serious and has no effective workaround. At the start of the ARRL DX CW contest on 40 meters I pounced on the first European station I heard. The QSO was never completed: halfway through the XM240 went totally silent and the SWR soared.

In disgust and already feeling awful with a cold I quit the contest. There was no way to be competitive in the all band category without this antenna. I did return the next day to do a single band 20 meter effort but the damage had been done.

I suspect this is a similar problem to what happened to the TH6 in the fall: a loose fastener on the balun studs or the driven element. When the wind blows it occasionally reconnects and I can use it. But it's unreliable most of the time. It typically cuts out when transmitting, probably due to sparking.

This problem cannot be solved by climbing the tower. The feed point is 11' out along the boom and the antenna is 10' above the TH6. It will have to come down for repair. The XM240 had been slated to come down last year but as with the TH6 it was put off for a year. Now I have to wait for spring weather to arrive. That will be no sooner than April.

The XM240 balun is not especially robust. After lowering it from the smaller tower the studs on the balun spun loose from the enclosure when I reattached the elements to the boom. The braid straps to the driven element are flimsy. Again, I only wanted a few months from it and my schedule was tight so up it went with what I thought was an acceptable repair job.

There is a parable about time that seems pertinent: time isn't something you have or don't have; time is something you make. I didn't make enough time for these antennas. The bigger and higher the antenna the more important it is to get it right. Maintenance is a killer.

In the final tally you'll end up having to make more time, and suffer the consequences when you most need the antennas. I'll try to do better. As things stand my contest season is over but for occasional forays. On the positive side, I have more time to plan and build in advance of the warm weather when antenna and tower work resumes in earnest.

20 Meter 3-element Reversible Wire Yagi

Recently I was asked to design a reversible 3-element wire yagi. The constraints were a maximum height of 30' (9 meters) and inverted vee elements. Since many hams do not have towers or tall supports this antenna can provide good performance in two directions on what is the workhorse DX band. For this reason I thought to make a few changes and write it up for the blog.

Although the antenna is simple and easy to construct it requires attention to detail. Unlike single element antennas such as dipoles, verticals and delta loops a yagi relies on coupling and phasing between elements to develop its directive pattern. Care is required when measuring the wires, getting the angles right and building the coils and switching system. Mistakes will incur a cost.

Another consideration is antenna placement. Because it is fairly low there is the risk of coupling to house wiring and plumbing, metal fences, power lines and so on. A minimum spacing of 10 meters (λ/2) of these obstacles is highly recommended, especially to the front and back. More height, if you can manage it makes this easier.

Design

The design is similar to that of a 3-element inverted vee wire yagi for 40 meters that I described several years ago. Refer to that article for aspects of design and construction that are not repeated in this one. The element spacing is 3.5 meters, for a total length of 7 meters.

The interior angle of the inverted vee elements is 90°. A larger angle will improve performance but don't try it without a redesign of the antenna since the resonant frequency of an inverted vee rises with larger interior angles. Elevation angle of the main lobe is lowered by bending a dipole into a vee since the average current height is lower. That, too, depends on the interior angle.

The elements are made from 2.5 mm (AWG 12) copper wire with 0.7 mm insulation. Thinner wire can be used since the tension doesn't need to be very high, however ohmic loss will be higher. The wire loss for the antenna as designed is approximately -0.4 db. There is ground loss as well despite the antenna apex being up almost λ/2 since the ends are much lower. Bare copper wire elements will need to be longer because the velocity factor of the insulated wire is ~2%.

Each half element (inverted vee leg) is the same length: 5.06 meters. To feed the antenna with a beta (hairpin) match the driven element legs are lengthened to 5.11 meters. Although you'd expect the driven element with a beta match to be shorter consider that the reflector element is in fact electrically longer. The beta match uses a nominal 150 Ω shorted transmission line stub at the feed point. The antenna radiation resistance is quite low at ~15 Ω mid-band. An L-network can be used instead but a beta match is simpler and lighter.

A 0.7 μH coil is placed at the centre of each parasitic element. Relays short the coil to convert the element from a reflector to a director. To allow use of the antenna without powering relays choose a preferred direction and place a SPST-NO relay at the reflector and a SPST-NC relay at the director. To reverse the yagi power both relay coils.

A larger value coil can be selected to broaden the 200 kHz 2:1 SWR bandwidth somewhat, but at the expense of gain. In my judgment the trade off is not justified. A switchable L-network at the feed point can switch the best match between the low and high ends of the 20 meter band. A tuner (ATU) can be used in the shack at the cost of additional transmission line loss. Unfortunately an antenna of this type is difficult to engineer to achieve a good match across the full band without significant performance reduction.

Performance

At the modelled height of 9 meters the elevation angle of the main lobe is 30° which is not ideal for DXing, if that is your interest. More height is needed to lower that angle. Like all yagis with 3 or more elements its performance remains stable at greater heights without the need to adjust the match or element lengths. However it will worsen at lower heights since the element ends are already only λ/4 above ground.

The free space gain of the antenna peaks at near 8 dbi high in the band, and is greater due to ground reflection as is true with any horizontally polarized antenna. Gain is quite flat across the band, increasing only 0.35 db from 14.0 MHz to 14.35 MHz. Although a 2-element yagi has peak gain only a little more than 1 db worse the gain bandwidth is quite narrow.

The F/B, though not exceptional, is quite good across the band and, again, far superior to a 2-element yagi. It peaks at close to 30 db mid-band. As is typical of yagis the frequencies of maximum gain and F/B do not coincide, and can be far apart. In this case over 150 kHz apart.

Parting thoughts

It is the rare ham who does not want more antenna performance. That is difficult to do in the urban and suburban settings where so many live. This antenna is a simple and inexpensive way to achieve performance on the ever-popular 20 meter band. It can be almost invisible to neighbours if there are trees. Trees can also serve as convenient supports.

The particular physical design described here was chosen by the intended builder. Your circumstances and needs may be different. The antenna design can be modified. However, guessing at the impact of changes to dimensions and construction materials is not recommended. Yagis require more care than that if performance is the objective. Modelling those differences is wise. A high quality antenna analyzer, and the knowledge to use it, is so valuable it can verge on being mandatory.

Spring, and therefore antenna season, is around the corner.

Dealing with Dits

A few weeks ago I received a preview LCR (log check report) for the recent CQ WW CW contest. There is a dreadful commonality among my LCRs for all contest: dits are my bane. Typical errors include:

• Confusing S and H, U and V, and A and U in call signs
• Confusing 3 and 4, and 6 and 7 in call signs and serial numbers
• Dropped E in call signs

I know I'm not alone in making these errors yet it still bothers me. You'd think that after decades of being a primarily CW operator and operating at high speeds in contests that I'd do better. Becoming proficient at high speed CW does come easy for some, while others like myself have to work at it. True proficiency can remain elusive. The problem becomes worse when fatigue sets in after long hours in front of the rig.

I'll keep practicing.

On the other side of the QSO the LCR tells a similar tale. You may have noticed that my call sign has a lots of dits: 11 of them. When I turn up the speed the other operator can miss one or two of them. Although I love my call -- it has a nice swing on CW -- during contests I envy those with less dits and more dahs, or at least not so many dits strung together.

Very few get the VE3 prefix wrong. Yes, some do at first hear VE2 or KE3, but that may be QRM rather than operator error. The prefix is so common that it gets copied by many as a single character. Indeed that is a common technique of proficient high speed operators, that of hearing character groups or short words as a single entity.

It's almost always the suffix that is the problem. The LCR list of busted calls on the other side of the QSO is always longer than the ones I make. I am sure this reflects the difficulty of copying all those dits rather than signifying that I'm a superior CW operator! I always correct their errors when they send my call. Since they rarely do that when I'm running I may have no idea that they've made a mistake and so I can't send a correction.

The most common copying error for my call sign suffix is UN. Other common ones are KN and WN, which may be more likely due to QRN or QRM where the space between dits may be unheard. Other errors are usually call signs of active VE3 contest operators that the other operator picked out of a master call sign database as a lazy way to deal with poor copy. I correct those as well, though a few race onward without listening or caring.

Since I often have to correct the other operator's mistaken copy I created a novel message that I can send with the press of a function key. Here's what it looks like when programmed in N1MM Logger:

F7 VE3-vn,ve3 >>v n<<

The prefix is sent at normal speed, then the suffix is sent 4 wpm slower with a space added before each letter. It works very well. I thought to create the function key only last year. It saves me so much effort I wish I'd done it sooner.

At least I don't have it as bad as HH2AA, 6Y5T and many others. The varieties of error people make with their calls is startling. When they get incorrectly spotted by a human or a CW skimmer their logs fill with dupes, from operators who don't stop to think or pay attention. That happens to me too. Since a VE3 doesn't attract quite as much attention I can deal with it.

A few of these stations with dit-heavy call signs have resorted to a trick similar to the one I use, to slow down part or all of the call sign in a contest CQ. From my side of the QSO it works well, and hopefully it works for them. Otherwise the slight decrease in QSO rate would not be justified. After all, it isn't their fault that they have calls signs with so many dits.

You might think that slowing down would solve these problems. It doesn't seem to. In my experience these dit errors persist at all speeds. A few stations with dit-heavy call signs have tried this and they don't appear to stick with it. Why bother slowing down and hurting your contest score if there is so little to be gained.

I would hope that those with a lengthy LCR listing of busted calls and exchanges feel motivated to improve their skills. That's the better solution. I know that I'm still trying.

160 Meter 3-element Tower Yagi

Last month I listed a few of the ideas I'm considering for a better and permanent 160 meter antenna. One of those is to tune my two big towers as parasitic elements for a wire driven element centred between them, hung from a catenary rope running between the towers. It's an interesting idea with a few novel attributes. I decided to flesh out the idea into a complete model. The time came free when I found myself confined indoors with a cold.

Although this antenna may never be built the concepts it contains are useful enough to be written up. It may give readers ideas of their own. Keep in mind that while few hams have huge towers the design can be scaled to higher bands; for example, ~15 to 25 meter tall towers on 80 meters.

Antenna topology

My big towers are 60 meters apart, with a line through them that points approximately northeast and southwest. For this region that covers the two most productive directions for contests: Europe and the US midwest and southwest. A reversible 3-element vertical yagi would do wonders for contest scores and top band DXing. With the towers detuned the driven element becomes an omni-directional vertical. Unlike my 80 meter array the parasitic elements (towers) cannot be floated, only detuned on 160 meters.

To simplify the model I made both towers 43 meters tall with a capacity hat to emulate the yagis at the top. The unfinished tower will in actuality be a slightly shorter 41 meters. The capacity hat is a rough stand-in for a mast and yagis. As we will see this is not critical since the towers will be tuned to the desired resonance. The physical height is more important in setting the aperture of the element and therefore the mutual impedances between elements.

In previous models I went simpler yet by making the physical  height the estimated electrical length of the tower. Each capacity hat has 4 arms of 6 meters length and 25 mm diameter. This is a good enough analogue to ensure the shunt feed design can be adjusted to the required resonant frequency.

As with any reversible yagi the driven element should be centred. The symmetry ensures equivalent behaviour when reversed, greatly simplifying switching, tuning and matching. Optimum performance requires the driven element to be offset toward the reflector. An ambitious builder could drop two wire vertical elements from the catenary and switch between them and detune the unused wire, thus achieve slightly more gain and F/B. I will not be so ambitious in the present design.

A "boom" length of 60 meters (0.365λ) is just about ideal for optimal performance of a 3-element yagi. It is no accident that my towers are this far apart; it was not the primary reason, but it was a consideration. Since it isn't easy to move a tower once it's been planted in the ground some forethought is recommended.

Ground model

My modelling software, EZNEC, allows a few alternative ground models. Vertical antennas and arrays can be greatly simplified by eschewing radials entirely by replacing them with a resistor that connects the vertical to ground. The resistor value should be set to the estimated equivalent ground resistance.

NEC2 does not support wire connections to "real" ground. Instead we must use MININEC ground, which for purposes of calculating the near field assumes ground is a perfect ground plane: zero loss and infinite in extent. Its equivalent resistance is 0 Ω, hence the need to insert a resistor.  Generating the far field pattern relies on the specified ground parameters -- dielectric constant and conductivity -- which we certainly need, but it is not used to calculate the near field.

Real radial systems have non-zero equivalent resistance and are therefore lossy. We want the most extensive radial system we can manage to minimize loss. In a yagi the loss is higher than in a simple vertical antenna because the radiation resistance is lower, and the radiation resistance and ground resistance are in series. Achieving an equivalent resistance lower than 5 Ω requires at least 50 to 60 λ/4 radials. With 8 radials the equivalent resistance is rarely better than 15 Ω, even over very good ground quality. The more extensive the radial system the less real ground affects loss.

Perfect ground is a true non-resonant ground plane. A lesser system made of finite length wires will influence antenna resonance. This effects the tuning of the elements, which we compensate for in the tuning procedure. If you later add more radials in future the elements must be retuned. The resonance effect of radial count and length was discussed in an earlier article. That and other work the article references can guide the physical design of an effective radial system.

Shunt feed tuning

Tuning an electrically long tower can require a more complex network than a gamma match. Fortunately the towers are parasitic elements so all we need to tune for is the reactance, leaving the resistance part of the impedance to find its own level. Not that the complex impedance is without impact, only that we can work around it.

I found that a 20 meter long gamma rod of AWG 12 wire spaced 1 meter from the tower (centre-to-centre) worked well. In the model the rod is 19 meters long since it begins 1 meter above ground.

Feel free to experiment with other arrangements. I deliberately chose these 1 meter values to be equal to the segment length of all wires, thus assuring the best accuracy of NEC2 calculations. Consistent with this constraint, longer wires are all an integral number of meters, and equal to the segment count. Notice that the gamma rod is a small fraction of a wavelength from the tower, a case where it is critical to have their segments aligned.

There are loads in the tower's bottom segment (also 1 meter long) and the gamma rod's bottom segment for the equivalent ground resistance and gamma capacitor, respectively. Were the tower fed by transmission line the feed point would be at the bottom conductive spacer. We will only put a source there temporarily when tuning the element. In the model the source is centred on the spacer because it has only 1 segment.

When I need to float vertical elements in models I ordinarily lift the wire bottom off the ground. Because that is awkward with a shunt feed I instead temporarily raise the resistance to 100,000 Ω. This works very well to isolate the element from ground. When actually tuning the tower neither of these methods may work. The tower base itself may behave as an Ufer ground, and the bundle of coax and control cables are a long radial. Instead try shorting the gamma capacitor, adding a parallel capacitor or disconnecting the gamma rod. I can't make a firm recommendation until I try it myself.

Tuning the parasites

Setting the self-resonance of the parasitic elements is the remaining critical factor to making the antenna work. This is far easier to explore with a computer model than on a real antenna.

First I selected a centre frequency of 1830 kHz, which is a little high for general CW DXing but about right for contesters who typically use the range 1800 to 1880 kHz for CW. In ITU region 1 it may be desirable to raise the centre frequency since 1810 is the lowest frequency allowed. I am also not interested in SSB on 160 meter, so I am not concerned that the bandwidth is not enough to function higher in the band.

As an initial estimate of the desired tuning I chose self-resonant frequencies of 1738 kHz for the reflector and 1922 kHz for the director. These are 5% offsets which typically offer a good compromise between gain and SWR bandwidth. As we'll see my choice worked out pretty well. For this exercise I did not try and compare other offsets. If I ever consider building the antenna I may do so.

The tuning procedure for the shunt fed tower is straight-forward. The driven element and the other parasitic element are effectively floated by inserting a 100,000 Ω resistance at their bases. Calculating element currents confirmed they are negligible in the floated elements. The source is placed in the wire connecting the bottom of the gamma rod to the tower, as was described in the previous section.

The self-resonance is set by experimentally adjusting the gamma capacitor. We are looking for an impedance of R + j0 Ω; that is, self-resonance is the frequency where X = 0. The R value is not critical to the tuning of the parasitic element. The capacitor settings were 310 pf for the reflector (1738 kHz) and 227 pf for the director (1922 kHz). In a real antenna a variable capacitor can be used to tune the element. Because tuning is sensitive (~0.5 pf per 1 kHz) the capacitor shaft must be well insulated to prevent your hand from effecting the tuning. Once tuned the variable capacitor can be replaced by a fixed capacitor.

A small difficulty

With the model fully done I tested it. All was not well, though not in a totally surprising manner. The yagi's performance data were favourable, but for a centre frequency of 1880 kHz. The parasitic element shunt feed -- gamma rod and capacitor -- is doing something more than just achieving self-resonance at the assigned frequencies.

This is not the first time I've observed this behaviour. Performance bandwidth offset appears to be a feature of yagis using loaded elements. This is certainly true of short elements, and in this case it is occurring with electrically long elements. The 50 kHz offset is 2.7% of 1830 kHz, or about half of the parasitic element self-resonance offset from the intended centre frequency. That's a large error.

I increased the gamma capacitor values on both towers in tandem (and in proportion) until I found the settings that centred the yagi on 1830 kHz. These are 340 pf and 276 pf for the reflector and director, respectively. I floated the other elements to discover the new self-resonance frequencies: 1697 kHz and 1875 kHz. Although quite different their ratios are identical, as they should be.

The reason for the different offset for loaded elements requires understanding how the parasitic elements in a yagi perform their task. It is not due to their self-resonant frequencies; what matters is the phase shift, and that is determined by the element's reactance at the yagi's operating frequency.

The self resonant frequency varies with degree and type of element loading. Longstanding rules of thumb for tuning yagi elements only apply to unloaded elements. In reality the self resonant frequency is unimportant, only serving as a tuning guide. With modern high accuracy antenna analyzers with can dispense with it entirely.

Performance

Ground loss is an unavoidable feature of any vertically polarized antenna located close to ground. This goes double for a low impedance antenna like a yagi. Again, recall that the equivalent resistance of the ground loss is in series with the antenna's radiation resistance and conductor resistance. The lower the radiation resistance the greater is the proportion of the applied power that is dissipated in the loss resistances.

I modelled the performance over a range of resistances, from 0 Ω (perfect ground) up to 15 Ω (typically 8 to 10 λ/4 radials over medium to good ground), in steps of 5 Ω. The impact of the radial system is starkly illuminated. Getting below 5 Ω requires at least 40 radials. Depending on your ambitions it can be very good investment.

It is assumed that the radial system is identical for all 3 elements. This isn't necessary, and it can be sensible to make the radial system for the driven element better than those for the parasitic elements. Current, and therefore potential loss, is greater in the driven element than either of the parasitic elements. This was demonstrated in more detail in the design of the 80 meter 3-element vertical yagi I recently built so I won't repeat it here.

As with any 3-element yagi the gain is maximum at the top of the range while F/B is maximum lower down. Although both suffer once you pass above the frequency of maximum theoretical gain, gain rolls off sooner because radiation resistance is lowest where gain is highest.

The antenna's gain relative to a simple vertical should be considered since it is a useful comparison baseline. Gain was plotted across the same range for the same values of ground loss. Ground loss is less than for the yagi because of the higher radiation resistance. Gain gradually increases with frequency as the driven element's electrical length increases.

The array can be put in omni-directional mode to cover directions other than those available from its reversible yagi modes. This is done by floating or detuning both parasitic elements and switching in a different matching network.

Matching

The feed point resistance of the yagi is quite low, especially with a low loss radial system. A matching network is required to convert the impedance to 50 Ω. I designed a simple L-network using TLW and inserted that into the EZNEC model. The following SWR plot was done for a 5 Ω equivalent ground loss radial system for all elements.

The 2:1 SWR bandwidth is 60 kHz. I targetted 1835 kHz for the best match hoping to achieve the best result. Raising it a little higher may be better. Notice how fast the SWR rises on the high end where gain is maximum and radiation resistance is lowest.

A broader SWR bandwidth can be had with a smaller radial system because its higher loss sums with the radiation resistance to proportionately reduce variation of radiation resistance and reactance across the band. That is a poor reason to skimp on the radials! Better to use a switchable matching network to eke more bandwidth on the high end of the range.

Details of the matching network are not described since every installation will be different and the tools to design networks are readily available. I recommend building the antenna, tuning it and then measure the impedance across the band. The matching network should be designed to achieve the lowest SWR curve across the desired operating range.

Further thoughts

With an excellent radial system this antenna has 5 to 6 db advantage over a simple full-size vertical. That's a lot on top band. It will easily improve contest and DX results. But is it worth it? After all, this is no small antenna: it's big, ugly and expensive. If you already have or are planning some big towers it is certainly worth a look.

This antenna only has two directions and we ideally want four (the pattern isn't sharp). The most economical way to add those is with T-top sloping verticals wires supported from the same catenary rope supporting the driven element. These are similar to those in my 80 meter vertical yagi, just like in the original K3LR 160 meter array you can find in ON4UN's Low Band DXing book. Additional mechanical support for the catenary and stronger wire for the additional elements may be needed.

There does remain a concern of interactions with antennas on the tower which could place significant energy into receivers using those antennas. Band pass filters are mandatory. Alternatively the towers can be left as is by dropping wires from the catenary for the parasitic elements. Coupling with the tower and cables will still occur but that may be more managable by, for example, detuning the tower and bonding coax and shielded cables to the tower at several points, or by running them inside the tower. Any coupling that does occur will influence the tuning procedure to a degree that the presented design does not address -- a simple model I built proved to be challenging in this regard, but was not conclusive. Correct tuning may have to be experimentally determined.

In all cases this antenna will require a switching system and control cables to allow direction and mode selection from the shack. There is ample material in the ON4UN book on how to go about it. After the switching system for my 80 meter vertical yagi is completed and in service I'll describe it in the blog and that can be used as a template for the 160 meter yagi.

I'd really like better performance on top band but I cannot realistically assign it more than very low priority. This was an interesting thought experiment that will be filed away. Who knows what the future will bring.

2019: Year of the Yagi

Waiting for spring

It's that time of year to look ahead and make my plans for the 2019 station construction season. I've made a habit of doing this every year, and you'll find a similar article about this time of year in the blog's archives. They are also among the least interesting for readers. However this blog is about more than engaging readers at all times; it is a tool for keeping myself honest.

Despite the inward focus it can still be of use to others who could benefit from doing the same, and then measuring their progress at the end of the year. The comparison can be both sobering and instructive.

My ultimate objective is a moderately competitive contest station suitable for both single op and multi op, while also fueling my daily operating habits of DXing and experimenting with new technology and operating aids. It is not intended to be a lifelong project. With some effort the bulk of the "heavy lifting" will be completed in 2019 or early 2020. Since there will be non-radio summertime activities I may not fulfill my entire plan. But it is important to have objectives and a plan to get there.

After failing to fully achieve my 2018 ambitions I remain cautiously optimistic that I can do better in 2019. The major construction project -- a 140' tower -- is more than half raised, and should be complete in early spring. The only substantial mechanical decision to be made with respect to the new tower is whether to go with a conventional heavy-duty rotator or to use my spare prop pitch motor. Construction of the mast and drive system must be complete before the top two tower sections leave the ground.

With that out of the way I can turn my attention to antennas, and antennas means yagis big and small. Indeed, that is the focus of my plan for 2019.

Building yagis

As with most everything in our stations we have a choice between build and buy. Buying can be new or used. Time is limited and none of us can build everything in a large station. I pick my places. One of those places is antenna.

I have booms built for one each of long boom yagis for 20 and 15 meters, and I have most of the material on hand to build identical copies of each. These 4 yagis are slated for the new 140' tower (40 m, more precisely) on these all important contest bands. The lower yagis will be fixed northeast, towards Europe.

Aluminum tubing is available in abundance from just about every industrial metal dealer. The trouble comes when specifying the alloy and the less popular sizes suitable for telescoping elements. For example, one outlet that claims to sell most everything in any length does not actually do so. Alloys are mostly the weaker non-structural and the selection of wall thicknesses and outer diameters is incomplete. Another outlet carries more suitable tubing but only in full 20' and 24' lengths and charges quite a lot for cutting. I would have to cut tubes in their parking lot to fit them in my car!

Another difficulty is acquiring 0.058" wall tubing in Canada. This is classed as aerospace tubing and has a limited market. I am revising mechanical designs and about to begin machining experiments to see what I can do with common 0.065" wall tubing. The rest I will import from the US.

Boom-to-element brackets are another area of concern. Although straight-forward to design and build it is the fasteners that are expensive. Each alone isn't, but I will require a large quantity.

I am searching for good quality and reasonably prices products which, again, will have to be imported from the US. Importing from the US ought to be simple but often isn't since many dealers do not specialize in international sales and can incur substantial brokerage fees. There are alternatives to get around the problem.

Once construction of the yagis is fully underway I will surely devote a few articles to the subject. Compared to many of the components of a large station yagis are relatively simple things. It's the details that can bog you down.

Tri-banders

With mono-band yagis for the high bands I will have surplus tri-band yagis, all Hy-Gain: TH6, TH7 and Explorer 14. I will likely sell the latter and probably the same for the TH7. I would then find another TH6 and stack them on one of the towers, possibly rotatable through 120°. I would use these at a lower height to cover the US and Caribbean, without risking interactions with the mono-band yagis higher up.

Side mounting these yagis is, in part, why I will replace the TH7 with a TH6. On the TH7 the dual driven elements can easily strike the tower when rotated. Further, the electrical design of the TH7 is not optimal for the CW band segments on 20, 15 and 10 meters. I don't want to mess around redesigning the antenna to do better on CW. The gain and performance is acceptable but not the SWR.

Although not the best antennas these large tri-banders will take a lot of the operating burden from their mono-band cousins, allowing instant switching between directions and still have a powerful signal wherever I need it. It's also far cheaper than alternative but will likely need to be refurbished. Getting the TH6 down from the big tower is necessary no matter what because one of the traps is exhibiting intermittent continuity.

80 meters

My vertical yagi project has been proceeding slowly. So slowly that it's almost been standing still. I further delayed working on the switching system due to the deep snow and cold temperatures. Now that the hours of sunlight are increasing and warmer weather approaches I intend to get going on it.

80m vertical yagi switching system - some assembly required

Ideally it would be ready in time for the upcoming ARRL DX CW weekend, but that is unlikely. I'll leave it fixed on Europe as I did in CQ WW CW. I configure it that way except for Pacific area DXpeditions and North American contests.

The 80 meter vertical yagi should be completed before the warm weather when my attention will shift to other projects.

40 meters

When the TH7 comes off the 21 meter tower (70') my plan is to replace it with the XM240. This would become my short path rotatable yagi for this important contest band, covering the US and more. But before it comes down from its current position at 46 meters (150') on the big tower I need to replace it with another 40 meter yagi.

Therein lies what is perhaps my biggest roadblock this year. I want to build and raise a full size 3-element yagi to go on that tower. That's a large enough project that it may be impossible to manage this year considering everything else that needs to be done. Indeed this antenna is why the prop pitch was installed on that tower.

It's entirely possible that there will be nothing up there in the fall. That is, if I can build a wire yagi pointed at Europe between the two big towers. That way I would not have a unbridgable gap in my 40 meter capability. Alternatively I could purchase another XM240 or similar yagi as a stop gap measure for the next year or two. Should the opportunity arise I may go for it.

10 meters

This is the least of my worries. I do plan stacked yagis for 10 meters on the 40 meter tower, with one 6-element yagi on top of the mast above the planned 40 meter yagi (where the XM240 is currently situated), and one or two more lower down fixed on Europe but preferably rotatable.

With the sunspots not reappearing to boost 10 meter propagation until 2021 this project will be fit in as time is available, after the other projects are completed.

6 meters

No changes are planned this year. The redesigned A50-6 at 24 meters will be my antenna for this year's sporadic E season. The only change will be the transmission line so that I can recover most of the estimated 3 to 4 db loss in the very old run of RG213 I've been using until now. The reason I've delayed replacing it is to save the Heliax I have for runs to and up the big towers.

If that supply problem is not resolved by April I will install a run of LMR400 up the tower from the antenna switch at the bottom. With the recent rewiring the run from there into the shack is a combination of LDF5 Heliax and LMR400, which is good enough for now.

In future years I would like more gain on 6 meters. This would either be accomplished with a longer boom yagi or a stack of two yagis. They will likely require a new tower. I have some thinking to do.

160 meters

I covered my options in a recent article. As a minimum I will replace the current antenna with full height wire vertical and at least double the current 8 radials. Every decibel I can scrape out of a simple and temporary antenna will pay big dividends. This was emphasized by the difficulty I encountered during the recent CQ 160 meter CW contest when marginal conditions kept a large number of QSOs and multipliers just out of reach. I don't want that to happen again.

Longer term I do want to exploit the towers to achieve gain on top band. I have been running models to explore alternative ways to corral them into either a vertical yagi or phased array. In addition to computer models I would need to experiment to ensure using the towers will not cause serious coupling into the tower mounted yagis, and from into the station. It is a solvable problem.

Receive antennas

The short west Beverage is a stopgap until I improve my low band receive capability. At the least I plan to twin the existing northeast Beverage to make it reversible. A north-south reversible Beverage is also likely. These projects could be put off because they are not mandatory until I run high power and attract many weaker stations. It is also not absolutely needed for 80 meters since the vertical yagi has very good directivity. Receive antennas are primarily needed for 160 meters.

A vertical phased array remains a possibility, if only to simplify maintenance and eke out the best directivity and selection of directions. I have not decided. The small number of planned Beverages will prove adequate until the rest of the station is complete. More receive options raises the possibility of diversity reception, which is a powerful technique for copying weak signals.

In the shack

As I demonstrated last month it is possible to do SO2R and multi-op with no automation or filters, for low power contesting. When I acquire an amplifier that must change. I have been putting off this work until it becomes unavoidable. There is also the prospect of more antennas which will exceed the capacity of my current switching system. When my 2019 tower and antenna plan comes to fruition there will be no more putting off the inevitable.

Automated selection of filters and antennas from two operating positions will be needed by the fall contest season. That will be quite a challenge since much of it will need to customized, a hybrid with commercial equipment. The filters will be bought and the switching system designed and developed by me.

I would like to arrange the first multi-op sometime during the next contest season. Station automation is required since it may be too much to ask others to figure out the unique manual control systems I currently employ. Physical rearrangement of the shack will also be necessary so that two people can comfortably operate together. Of all my challenges this will be the easiest to accomplish.

Transceivers are going to change. I expect to sell both the KX3 and FT950. The FTdx5000MP will remain for one operating position and the other will be a K3 or similar high end transceiver. I will still be able to operate QRP by turning the power down to 5 watts (but not on the 5000 which has a minimum power of 10 watts). Although the KX3 is a wonderful rig I am becoming increasingly frustrated by its limitations; it is not suitable as a high performance base station rig.

For competitive use the FT950's DSP filtering is too noisy and rings and the receive audio is noisy. It has been surpassed by subsequent generations of equipment. I have kept it around to experiment with SO2R and as a backup for the main transceiver.

As with previous years my 2019 plan is ambitious. I have set my objectives and now must do my best to achieve them. That I will probably fall short does not deter me from aiming high.

Administrivia

Google has not only abandoned Blogger development they are also in the process of shutting down Google+. The latter is not of concern to me other than it will mess up reader comments and possibly some lesser things. I won't know until it happens. Anonymous comments unfortunately remain prohibited because every time I allow them there is a flood of spam. I apologize for the inconvenience. It's because of this problem that comments are moderated.

As many have discovered, direct email is the best way to reach me. Those I reply to. Comments on articles are routinely approved although I might not reply to those. Blogger may eventually become unusable and I'll have to find a new home. That would be an unwelcome burden and could kill the blog. But for now it's business as usual.

Short Beverage Antenna for 160 Meters

One of the many projects I did not get done in 2018 was putting up more receive antennas for the low bands. The delay is due to its relative priority being lower than transmit antennas, such as my still not quite complete 80 meter vertical yagi.

Up to now I have just the 175 meter long Beverage antenna pointed northeast at Europe. It's a wonderful antenna, although one that requires periodic maintenance. That's a common complaint about Beverages strung through bush and forest. The area was selected because it is far from sources of potential interference and it is only populated by wildlife. The farm fields are easier to work in but would require taking the Beverages down during spring and summer.

With the upcoming CQ 160 meter contest as motivation I spend some time last week putting up a temporary Beverage pointing west. It is shorter and simpler than what I have planned for a permanent antenna. What it therefore lacks in performance is compensated by the reusability of its components (even the wire) and ease of construction. By "ease" I mean relatively easy compared to alternatives.

The Beverage is ~89 meters long, about the shortest a Beverage for 160 meters can be and still deliver acceptable performance. That length is not randomly chosen. Like yagi booms there are lengths that exhibit peaks in F/B, and therefore directivity and noise attenuation. To demonstrate this I selected three lengths -- 70, 89 and 110 meters -- and modelled them with EZNEC. The impetus for the modelling comes from ON4UN's book Low-band DXing, in which optimum lengths are discussed.

Notice the differences. F/B is significantly better with an 89 meter length. However gain increases (beam width decreases) with length. There is a peak in F/B approximately every multiple of 89 meters; gain continuously increases as the length increases. Gain is not too critical since, if needed, it can be provided with a pre-amp. The length does not have to be precisely 89 meters. A few meters either way has little impact on performance. The small difference in F/B is likely swamped by other variables such as ground quality.

The gain difference is noticable. The modelled gain of the 175 meter Beverage on 160 meters is -10.5 dbi versus -15.1 dbi for the 89 meter Beverage, or -4.5 db worse on the shorter and lower antenna. About -0.5 db of that is due to the lower 1 meter height of this antenna. (There is another -1 db of coax loss, as we'll see later.) The additional loss is enough to make comparisons between the Beverages difficult. Of course the gain is not indicative of the antenna's directivity, and therefore its effect on copy of signals in the target direction.

Feed point

In the spirit of keeping it simple for this temporary antenna the feed point is built into a discarded plastic food container. The clear plastic helpfully shows all of the components, inside and outside, but does confuse which side each is on. The inside only contains the matching transformer. Stainless steel hardware provides studs to attach the Beverage wire and groung wire. I am using UHF connectors since I have them and I don't have type F bulkhead connectors.

The ferrite core and construction are the same as for the northeast Beverage. The turns ratio of 5:2 is a good match between RG6 (70 Ω) and 500 Ω for the antenna. This was tested with a 470 Ω resistor which measure 495 Ω. A better match is possible with a turns ratio of 8:3 but I got frustrated trying to thread more turns through those tiny holes in the BN73-202 binocular core. This is despite using thin AWG 24 insulated wire scrounged from old Cat5 cable.

With the cover on the container it is pretty well watertight when the lid faces up. Otherwise water could seep in around the studs and SO239 connector. Sealant is near useless due to the flexibility of the thin plastic.

Termination

Driving the ground rods into frozen ground is not fun. After a couple of weeks of extremely cold weather and thin snow cover the frost has penetrated deep. I used a pick axe to remove the top 10 cm of frozen soil. That was enough to hammer the rods through the remainder of the frozen soil into the warmer ground below. However I did encounter rocks that required repeating the process several times until I could get down the full 4'.

I did not use a 470 Ω resistor for the termination. After reviewing material on Beverage antenna construction I realized that I had to compensate for the serial resistance of the ground loss. With a single ground rod this can be exceed 100 Ω even in good soil. I opted for a 330 Ω carbon composition resistor that measure close to 350 Ω (carbon composition resistor increase in value with age). This worked out well when I measured 495 Ω at the feed point from 1.5 MHz through 7.5 MHz.

I kept the construction simple. The resistor is clamped directly to the ground rod. A wire nut connects it to the Beverage wire. Since the wire swings a bit in the breeze I dropped a piece of scrap lumber on it to avoid breakage due to metal fatigue.

The wire tensioner uses a thin nylon rope and a cleat made from a couple of nails pounded in a tree. The feed point end of the wire is secured to a wood fence rail with a nail driven through the insulator. It's simple, cheap and effective.

Beverage wire and siting

I used what was available and long enough: AWG 14 THHN solid copper wire. I have a 300 meter reel from which I've been building my wire antennas. When the Beverage is removed in the spring the wire will be reused for other wire antennas. The insulation allows the wire to sit directly on trees and wood fencing without risk of performance degradation.

The Beverage wire runs along the wood fence line about 1 meter off the ground. There is little to no risk of deer or humans tangling with the wire, other than yours truly. I climb the fence to get to work on the 80 meter array. Because the coax and control cable for the 80 meter antenna cross the fence the Beverage passes close to them. While the Beverage performance should not be affected by the proximity there is a risk 80 meter transmission into the Beverage when operating SO2R on 80 and 160 meters concurrently. I have not tested this yet.

The 150' tower is as close as 25 meters to the Beverage. The tower and antennas are not resonant on 160 meters and the separation should be enough to avoid Beverage pattern distortion even if the tower were resonant. The 80 meter array elements are closer but are not resonant on 160 meters. However if the Beverage is used on 80 meters there is a risk of interaction. First listening tests on 80 meters don't demonstrate cause for concern. The southwest radials get close to the Beverage, although those of the 160 meter vertical (gray circle to the south) are 20 meters from the feed point.

Coax for the northeast Beverage (feed point at the northeast corner of the site map) runs along the fence line on the ground, as far west as the Trylon tower in the house backyard. Therefore they overlap for ~30 meters. This is generally poor practice due to the potential for noise incursion but difficult to avoid in this instance. The RG6 coax for the west Beverage angles south into the hay field, running midway between the 160 meter radials and the Beverage.

Terminating the Beverage further west to reduce all these interaction issues was inadvisable because it would bring the antenna close to the power line that runs through my property (indicated by the gray line). The drop to the house runs underground along the forest of young tree south of the driveway.

These pictures illustrate how the fence is being employed for the west termination (left), supporting the wire and the east feed point. It's as simple as it looks. Laying the line on the fence rails took a couple of hours of walking through the undergrowth with a wire reel, cutting branches and thorns along the way. The deep snow and slush didn't help. The bush on the verges of the hay fields has grown thick over the years due to not being maintained. I am unlikely to change that.

Initial on air testing

I had one evening with the antenna before the CQ 160 contest. Testing was limited due to finding few stations far to the west to properly. I compared it to the vertical itself and the northeast Beverage. At least the large number of Europeans active in preparation for the contest made it easy to establish that the F/B of the west Beverage was reasonably good, perhaps as much as 20 db. That indicates the wire length is performing in accordance with the model.

Later in the evening I heard a W6 and a couple of W7's. The Beverage definitely improved the SNR on those stations. While promising, this was only a tentative assessment. I would have to wait for the contest to have lots of activity and a range of signal levels to better assess its performance. The directivity is better on 80 meters, but again there was a dearth of suitable stations available to get reliable comparison data.

Since I used the full 150 meter roll of RG6 there is an estimated transmission line loss of ~3 db. The extra length was coiled up outside -- it will later become a bidirectional Beverage. The loss is not a great inconvenience other than to make antenna comparisons more difficult. A lesser impact is that the periodic impedance variation with frequency is mostly smoothed away when measured in the shack.

Contest performance testing

Hundreds of stations audible at any time from all over North America and around the world is a fantastic environment in which to conduct an antenna test. Mediocre to poor DX conditions on Friday night were helpful in providing many weak signals for testing, although it was damaging to my score. Late in the evening when west coast activity peaked was the best time to test. It gave me something to do after largely working out the east coast and being unable to work many Europeans.

The TLDR version of its performance: meh! This is about the shortest Beverage you can have on 160 meters and get anything approaching good performance. Although I have not done a direct comparison it is visually apparent on looking at the far field patterns of this and a compact antenna such as a Flag or K9AY array that performance is comparable. One important difference is that the compact antennas require a pre-amp, which in some cases can create noise during SO2R and multi-op contesting.

Despite having a broad azimuth pattern the antenna performed best on VE7 and northern W7 and W0. Reception of W6 stations was slightly improved but very little on W5. I doubt that I would have missed any QSOs during the contest without this antenna but it made easier copy. No Pacific stations were heard. That test will have to wait.

One disadvantage of the overly broad pattern is that the F/S is poor. W2, W3 and W4 stations showed little improvement with this Beverage and were not notched as they are with the longer northeast Beverage. Removing QRM, not just noise, is desirable in a receive antenna. It did reject signals well off the back, but all I have off the back is Europe and, sadly, there was no QRM from that direction.

Initial tests on 80 meters are promising. Directivity is superior to that on 160 meters due to the antenna being twice as long relative to wavelength. It has been used just once in daily DXing, during a sunrise Pacific opening (I don't often wake up early enough for these!). It made a modest improvement on VK3 and E5 signals, which are more southwest than west from here. I suspect that the modest result is due to atmospheric QRN predominantly coming from the southwest. But I could be wrong.

There are upcoming contests where I expect it to assist with adding multipliers on 80 meters. As yet I have nothing conclusive to report about performance on 40 meters. Another reception tool would be welcome on 40 due to the poor directivity of the XM240.

Future plan

This experimental Beverage antenna will come down in the spring. As an experiment is has already proven fruitful and I expect to get more out of it for the rest of the winter. The wire and coax will be recycled into other antennas and the transformer will likely see service in another Beverage. The plastic container will be discarded (recycled) since it won't survive the weather for long.

Many low band enthusiasts have replaced their Beverages with switchable vertical arrays, which can achieve equal or better directivity with a smaller footprint. But they're more complex, requiring hybrid combiners, phasing harnesses and amplifiers among other specialized components. Most opt for commercial products. As I said earlier, these arrays need to be well separated from transmit antennas to avoid the potential for grief from the pre-amps.

I am on the fence regarding Beverages versus vertical arrays. This is a choice I'll have to made by the fall. Regardless of that decision I am very likely to twin the northeast Beverage to make it bi-directional. Ultimately that may be my only Beverage.

On Surviving a Solar Minimum Winter

VE3 winters are long and cold. This far north that is often true of the HF bands as well. Although my geographical latitude is not all that high at 45°, the auroral zone is nearby and is frequently responsible for partial radio blackouts on the most productive DX paths. It can be frustrating to hear stations only a few hundred kilometers south working Europeans and Asians I can barely copy, if at all.

Lack of sunspots makes it worse. The openings on 20 meters are short, limited to the brief hours of daylight. It gets even worse on 17 meters, and 15 meters doesn't open at all much of the time. On 10 meters there is feeble sporadic E and the occasional South American.

Going lower helps. However 30 and 40 meters close early as the MUF drops like a rock after sunset. As partial compensation the polar path, when the auroral absorption permits, does bring in workable stations over the pole from Asia and Europe for several hours every morning. But if you only have a simple antenna these weak ones are difficult to work. My high yagi helps, and high power would produce more reliable results.

The lowest bands are often good, which many hams embrace with enthusiasm. Although I enjoy DXing on 80 and 160 meters all that QRN gets to me. During the NAQP SSB contest this past weekend one ham remarked how nice it was to put a voice to my call since I am mostly on CW. I am avoiding most phone contests because my brain gets rattled by the noise and difficult copy due to the wide bandwidth needed for SSB.

Many days I avoid the bands entirely to recuperate from the strain of operating the low bands. Although this ought to increase time spent in the shop working on antenna projects I find that my enthusiasm is muted. Progress is being made but not at a pace that the available hours would allow.

The important thing is not to fret too much about it. Some downtime during the year can contribute to sustained interest over the long term. Soon the days will grow long and the weather will warm up. On a slightly longer trajectory the sunspots will return. Not much will change in 2019, so we must look ahead to 2020 when solar cycle 25 will flex its muscles. Before long the high bands will be hopping.

In the meantime I am learning to love 160 meter DXing. There is DX to be found every night, and less frequently there can be enhanced conditions. Several days ago I switched on the rig near midnight just before heading to bed and I heard a few strong Europeans. So I called CQ. To my delight the DX rolled in, to the tune of 22 Europeans logged over 40 minutes. The only problem being that I was so sleepy my CW fist was poor.

To mix things up I like to add challenges to my operating. One example, in tune with the low sunspots, I operated QRP for the Stew Perry TBDC contest a few weeks ago. During my brief operation I was able to put 12 Europeans in the log, including a best distance of over 8000 km. Not bad for 5 watts on top band! Achieving the highest point QSO in the contest by working 3V8SF (who operated low power) was icing on the cake.

It is little things like this that get me through a solar minimum winter. Other hams choose different tactics. VHF/UHF enthusiasts are so isolated from the solar cycle they don't see what all the fuss is about. For them every day is a challenge.

There is really no point to this article other than to emphasize that an ebb and flow of energy and enthusiasm for the hobby is normal and not a cause for concern. Shutting the shack down for awhile is okay. Socializing with your fellow hams is also anodyne, during which you can commiserate on the poor conditions and encourage each other on your respective projects.

The physical strain of digging out of the recent fierce snowstorm is also refreshing in its way, despite the frigid weather. It's -25° C midday as I write these words and the wind is howling at 40 kph. Brrr! I'm glad my rotators are greased for these conditions. Soon enough the sun will return. As evidence of this 20 meters is once again opening to Japan and UA0 late in the afternoon rather than going dead the moment the sun dips below the horizon.

With the CQ 160 contest coming up this weekend I am fighting the doldrums with a quick and easy project that will pay dividends: another Beverage antenna. Stomping through the frozen thorn bushes and snowdrifts stringing wire and coax with half numb hands in order to battle the elements and poor conditions, when followed by a hot mug of fresh-ground coffee is highly recommended for lifting one's spirits.

Bare Bones SO2R

Single-op two-radios (SO2R) must almost seem perverse to non-contesters. At least that's my experience when the subject comes up in conversation. For contesters with the ambition to compete at a high level it has become a necessity. It's a necessity because our competitors are doing SO2R and are significantly boosting their scores.

It isn't easy. Aside from the technical challenge it requires practice to become effective. It can be mentally gruelling. The truly talented are able to run on two bands simultaneously, and their results are impressive. Like any competitive event, be it sports or radio sports, winning is hard work. In other words, if you find contesting easy or comfortable you're leaving points on the table because you could be working harder. There's nothing wrong with taking it easy, provided you don't care about winning.

SO2R rookie

During this past weekend's NAQP CW contest I had my SO2R debut. In one important way it was the ideal contest to do this: all competitors are limited to 100 watts. Therefore I could measure myself against both my expectations and the results of better contesters, after accounting for station size and geographical advantage. I can definitely say that it helped, increasing my score at least 10% if not 20%. It is no surprise that contesters with well-honed SO2R skills ran circles around me.

Operating SO2R along with its advantages and disadvantages is a topic I must push off to the future. I am as yet unqualified to discuss it. In this article I will show how I added to and configured my station to be SO2R capable. This is about as simple an SO2R as you'll find anywhere. It is just enough to give it a try with minimal effort and expense. I'll go further when I'm ready to do so.

Operating position

The display is front and centre, right where I believe it ought to be. I remain entirely skeptical of contesters who put the rig in front and the display on top. As the station and operator improve the rate also improves, including near continuous running, requiring less attention to the rig. It's just type, type, and more typing.

You will fatigue far faster when you have to constantly lift your neck and eyes to that degree as your attention flits between display and keyboard. Most modern contest software enable keyboard control of common rig features. One of the most used is RIT as stations call off frequency and your filter is narrow to manage congested band conditions. Controlling that by keyboard is a tremendous stress reducer.

You will likely notice a few problems with placement of some items. Of this I am aware and they will be dealt with. Perfection is nice but not mandatory, so I went with what I had for this first outing. The FT950 is not a good contesting rig because the receiver performs poorly and the DSP filtering is several generation old. But it was there and just gathering dust as a backup rig. I'll get something better later.

Antenna switching

Station automation is lacking and remains on my lengthy task list. For the present a manual switch controls the remote 2 × 8 antenna switch. Left and right radios have their respective switches on the top row of the enclosure. Antenna positions are identical on both sides. Hardware interlock in the antenna switch prevents the disaster of one antenna being selected on both sides.

The rotary switch has 6 positions: 4 allocated to antennas and the extreme right and left positions select no antenna. Outside of contests the second radio is normally at the latter setting. The switch next to the knob selects between antennas 1-4 and 5-8. By careful placement of antenna ports a desired antenna for a given band is almost always one step or switch click away.

On the bottom row there are blanks. The rotary one on the left is reserved for selecting the direction of the 80 meter vertical yagi. The one on the right will eventually be used to select receive antenna direction. Both radios will share the receive antenna. That's okay since it will most often only be needed for 160 meters.

RF interactions and filters

Most of my antennas are not adjacent, and that helps manage fundamental and harmonic interference with the other radio's receiver. This is important since I do not use band pass filters. Many contesters will be shocked by this yet it was common many years ago. I fondly remember running two kilowatt stations side by side during multi-op contests and having to coordinate with the other operator to avoid having the lower band station's harmonic clobber the other operator.

Yes, sensitive receiver front ends can be damaged. Although it has happened to me the fix was to replace the small incandescent lamp used as a fuse in the antenna line when it took the brunt of the abuse. A spare transceiver was always on hand for swapping in when this happened, and so avoid more than a few minutes of down time.

With 100 watts the risk of receiver failure is quite low. The greatest risk is when yagis on the same mast are in use by each station. The fundamental and harmonics can be very strong. The higher end rigs used by contesters usually have low-Q front-end filters ahead of the pre-amp that apply enough attenuation of the fundamental signal from a transmitter on another band to avoid a catastrophe or fundamental overload. The FT950 on the right is more susceptible than I like.

Band pass filters help in two ways: attenuate harmonics from the transmitting rig and attenuate the fundamental energy on the receiving rig. If you use an amplifier it will happily regenerate harmonics that the filter removed since no amplifier is perfectly linear, and this is even more so with RF power amplifiers, especially solid state amplifiers. Amplifier harmonic reduction requires tuned stubs or high power (and expensive) band pass filters.

Before the contest I ran through every combination of antennas and bands on both rigs to test for harmonic energy. All was as I expected. The worst case was transmitting on the 40 meter yagi where the second (20 meters) and third (15 meters) harmonics were very strong on the TH6 3 meters below it, hindering effective use of segments of those bands. The easiest solution was to switch to the TH7 at half the height.

Even with the best filtering there will be band segments wiped out by harmonics. It helps to run at a higher frequency on the lower band so that the harmonics on the higher band are less likely to be encountered. I made this mistake numerous times during the contest.

Audio switch, and using it effectively

One week before the contest I built a manual switch to feed receiver audio to the headphones. The wiring is straight-forward and can be easily figured out by anyone wishing to build a similar unit. There are stereo 3.5 mm jacks on the back for the left and right radios and one in the centre for the headphones. A splitter on the headphone jack can direct headphone stereo audio to a recording device, which is strongly recommended for top competitors in major contests.

The SPDT switches on top correspond to the headphone earpieces: left for left ear and right for right ear. Both switches to the left puts audio from the left radio into both earpieces, and vice versa. When listening to both radios at once the typical switch positions are left rig on the left earpiece and right rig on the right earpiece (as shown above). To concentrate on one radio the audio can be temporarily switched to both earpieces.

I put the switches on top because this is the best ergonomic fit for me. They're a short reach for my fingers that are constantly hovering over the keyboard.

A lot of switching goes on during the contest! The best SO2R control boxes will, under software control, switch the audio for the rig in receive to both earpieces when the other is transmitting, with an option to blend the audio in various ways to accentuate, say, the run radio's audio or to monitor the transmission side tone (CW) at a reduced level.

The way I blend audio is with the AF Gain controls on the rigs. I set the rig side tone level as low as I can while still being able to copy it. The side tone let's me know the progress of memory transmission or for feedback when using the paddles. Experienced operators disable the side tone during memory playback. There is no provision for a microphone. Transmit audio switching is more complicated and my favourite contest mode is CW. The WinKeyer USB takes care of rig switching under control of N1MM Logger+. The software ensures that just one rig transmits at a time in compliance with the rules of virtually all contests for single op entrants.

Ordinarily both audio channels from HF transceivers are identical. For radios with two receivers the stereo wiring brings the benefit of dual receive with no added effort. Split operation is rare during contests but can happen, so you'll be prepared. More common is to use the second receiver to search for stations on the same band and antenna, either while running or to double your S & P potential. This can be useful when sunspots are absent, such as now, when only one band is consistently producing contacts, or for single band contests. I may try this in the upcoming CQ 160 contest.

Don't be surprised if you hear power line hum when the audio switch is connected to both radios. Make sure the interconnect cables are high quality and that there is a low RF impedance bond between radio chassis and other equipment powered by the mains. I had a low level of hum only in the FTdx5000 audio which I traced to the headphone jack and in particular the 3.5 mm to ¼" adapter. Replacing it with a high quality unit resolved the problem. You can learn much more about trouble-free audio interfacing from K9YC, starting at page 40 of the linked document.

In summary, the audio switch is simple and it works. For an investment of a few dollars and a couple of hours it gives me a good entry point to try out SO2R. When or if I go all-in for SO2R a more substantial investment on a control box will be warranted.

Software

N1MM Logger+ software is smarter than I am. The SO2R features have been designed by contesters who have learned from their own long experience and feedback from the world's top competitors. The choices they have made are good ones. The challenge for an SO2R novice is to understand and use them effectively. I have much to learn.

The software chooses where next to transmit (left or right radio) and position the text cursor from context. It is not what you might expect or guess. It all makes sense once you get used to it. I wasn't used to it so I made many mistakes. As the contest progressed my error rate declined. You can learn a lot in just a few hours. There is nothing like a real contest to spur learning, far better than offline practice (which I also did).

The SO2R feature is well documented so I will simply point you there. Other popular contest software packages support SO2R as well, including interfacing with external control devices. I am obviously making use of the minimum set of features to get started with SO2R. This will change as I progress to phone SO2R, a superior audio switching system and more aggressive operating, including simultaneous running on two bands.

One feature I plan to make use of soonest is two keyboards, one for each rig. When done properly there is less fatigue and fewer typing/transmitting errors.

Distractions

At first it can be difficult to concentrate on copying the signal heard in one ear and not be distracted by what's being heard in the other ear. A momentary lapse means requesting a repeat, resulting in lost time for you and the other station.

Other types of distractions I experienced include:

• Sudden appearance of a noise burst or a loud signal in the other receiver.
• A CW tone close to or equal to that of a signal in the other receiver can be disorienting.
• Locking your attention on a weak caller takes longer when you're listening to both receivers.
• Poor timing of transmissions can have you paying attention to the wrong side. For example, answering a CQ on one rig a second or two after your CQ on the other radio ends. You're focussed on making your call and fail to copy the station calling you.

Put in the time and you'll get better at dealing with these and other distractions. The danger is that you become so anxious about mistakes that you abandon SO2R entirely. Don't do that; don't be afraid to make mistakes. It's better to stick with it and climb to the top of the learning curve. I know that I have more climbing to do, and I will surely make many more mistakes.

Whew!

It sure was nice when the contest ended and I could get a proper rest from SO2R. Several times during the contest I retreated to a single radio to reduce the stress level. It is not necessary to use both rigs all the time, especially in a long contest. As proficiency improves the stress will become managable. That's when you can challenge yourself to accomplish even more with SO2R.

I am considering a follow up article on the the nuances of SO2R and how some (not me!) push themselves to the maximum effort, and score. NAQP is a contest where SO2R makes a difference unlike most other contests. For once it was nice not to have the lowest score among my more exalted team members, which includes two WRTC competitors. I salute them.

Now it's on to practice, practice, practice. I intend to do SO2R again, though hopefully in a contest not quite so intense. My bare bones SO2R setup will transition to one more sophisticated as my schedule permits. Most of what is built for SO2R is needed for multi-op contests --filters, switching, automation and software -- and that I intend to do by the end of 2019. For now I am happy that I can achieve some of the potential score boost due to SO2R.

I hope I have inspired others to try SO2R. The thing is you don't have to do SO2R 100% of the time. Like beginning runners, you can alternate walking and running until your body is tough enough to go the distance. Pick your places and you can increase your contest score from a modest effort. With the availability of off-the-shelf software and hardware to take care of SO2R mechanics it's never been easier. Others are doing it so why not you.

Permanent 160 Meter Antennas Under Consideration

When you have a tall tower it is quite easy to put up a high performance wire antenna for the low bands. My 160 meter antenna is a good example: a catenary tied off at the 40 meter level support a slanted T-top vertical that performs remarkably well. In the most recent Stew Perry TBDC in which I operated QRP I was able to work numerous Europeans, with my best distance slightly over 8000 km. Imagine if I had more than the present 8 × 30 meter radials.

Because it's a temporary antenna it will not see further improvement. I would like to do better on top band with a better antenna. For almost all of my ham career I had no antenna for 160 meter so I am now making up for lost time. My contest scores depend on it, as does my pursuit of DX.

My antenna is temporary because it has to be taken down from mid-spring to late summer -- a minimum of about 4 months -- due to the incompatibility of radials and hay harvesting. It is not only a better antenna I need but preferably one that is permanent. These two requirements -- better and permanent -- are not easily accomplished. I will be happy to have a better part-time antenna and a modest though permanent one.

To this end I am actively investigating options. In this article I'll run through what are, so far, the best of them. I think it is worth taking the time to blog about it because there are sure to be others in a similar situation. The ideas may be of wider interest. But to be clear, this is primarily about my station, my operating objectives and my constraints.

Independent full size vertical

This may be the ideal solution. It requires a new tower of at least 30 meters height, well separated from the two big towers and receive antennas. The former requirement is to ensure enough structural strength for a physical ¼λ vertical, which is 40 meters high. The latter is to avoid destructive interactions and coupling which would distort the radiation patterns of the vertical and the receive antennas.

Separation ought to be at least 1λ, which is 160 meters (500'). That's a lot! Fortunately I have the space. Otherwise it may be necessary to dynamically de-tune towers when operating on 160 meters. Some do this on transmit, but if the array is directive you need to do it on receive as well; that is, full time.

My neighbour would likely be annoyed by this antenna since it takes at least 1 acre out of hay production unless I undertake the herculean effort to bury 2000 meters of radials. The area is trebled or quadrupled should I go further and make a 4 direction, 3 element vertical yagi out of it of the same type as my 80 meter array, just as K3LR originally designed. Again, I do have the space were I crazy enough to go for it.

Limiting the tower to 30 meters height would keep the guy stations out of the forested areas at the east side of my property. A 10 meter high stinger makes completes the monopole. The radials can extend into the forest, with some difficulty. The difficulty is multiplied for a yagi.

The areas where it can go (see the site map) are to the semi-enclosed areas east and southeast of the 150' tower or north of the 80 meter array. Elsewhere are swamp, forest, power lines or other towers and antennas. Feed lines would be very long, which is expensive and inconvenient though not a significant loss risk at 1.8 MHz. Many hams with the land put their 160 meter antennas far away to avoid all these problems. My receive antenna field is close, probably too close, to the east area.

Then there's the expense and maintenance for a tower. In sum, I really dislike this option. My ambitions for 160 meters are not grand enough to justify it.

Shared radial system

The 80 meter array has a large and connected radial system that covers a full acre. The radius is ~25 meters. Although this is a little short for 160 meters there is a lot of copper on the ground. Sharing the 80 meter antenna is an option I've discussed before and tentatively rejected because of the challenge of preserving performance on 80 meters.

There is one more option to consider now that the antenna is up and I know what I have to work with. By placing a switchable coil at the top of the tower, electrically inserted into the stinger, there would be negligible degradation of 80 meter performance and 160 meter performance may be acceptable.

The stinger will need to be electrically isolated from the tower. A thick wall fibreglass tube or solid rod would have the necessary strength. There are enough wires in the control cable to accommodate a signal to switch in a matching network and to operate a vacuum relay to switch in a coil at the top of the tower. A vacuum relay is mandatory due to the high voltage that high up the monopole.

According to the model the coil will have a substantial inductance of 105 μH to be electrically equivalent to a ¼λ. The higher up a monopole the inductor is placed the higher its value needs to be. It is important to design the coil with the greatest feasible Q to minimize loss. The inductor has a reactance of 1200 Ω at 1.825 MHz, giving an ESR (equivalent series resistance) of 6 Ω for a Q of 200, or 3 Ω for a Q of 400. Recall that R = X / Q. Since the higher Q can be difficult to achieve for a coil this size I will assume with the lower value.

A reasonable assumption of 5 Ω ground loss for the full 80 meter array's radial system at 1.8 MHz the loss antenna loss is -2.5 db. The additional coil loss is -1 db. These values are rough estimates. The pattern shows the impact of these losses. The capacitance hat in the model has negligible affect on the required coil inductance due to its small size. A larger hat affects 80 meter performance because it comes too close to the parasitic elements. It may be best to remove them entirely.

It is no surprise that the SWR bandwidth is poor. There is a span of 35 kHz with an SWR below 2. An L-network in the model optimizes SWR at 1.825 MHz, which is close to the centre of the band segment of most importance to me.

It is entirely possible to place the coil lower or entirely forego it by adjusting for the low impedance in the matching network at the base. In either case the antenna efficiency will be lower due to the coil and network loss, and the effectiveness will be lowered due to most of the antenna current being near the ground. A coil up higher put more of the current up higher. It's just that the latter is more difficult to build and switch.

Of course the antenna cannot be concurrently used on 80 and 160 meters. This is a problem in contests were there are no other antennas for these bands. But for the benefit of a year round 160 meter antenna it is of interest to me despite this constraint, the poor bandwidth and the loss.

Between two towers

I have written previously about the presence of an interaction between my current 160 meter antenna and the 150' tower from which it hangs. The physical height of the tower and mast is ~47 meters. The electrical length will be substantially more due to the top loading of the yagis, at least 55 meters. Although not resonant at 1.8 MHz it does distort the pattern a small amount by acting as a weakly active reflector. The estimated gain reduction towards Europe is approximately 2 db.

This is a significant amount for working stations in that direction, and there is little recompense in gain towards the opposite (southwest) direction. I would like to correct the problem. Regardless of what I do the antenna must be temporary due to haying during the spring and summer. But I'd rather have a good temporary antenna than a mediocre one.

To begin this exercise I placed a wire vertical centred between the two towers, which are 60 meters apart. The 30 meter spacing is ~0.18λ, a little more than is ideal for yagi spacing. The towers are modelled as 50 meters high with poor grounds of 25 Ω, representing the lightning ground with no radials. The resistance lightning sees is lower, but the near field of a 160 meter antenna involves a large area of lossy soil.

The antenna radial ground loss is 10 Ω, representative of a mediocre radial system, on the order of what I have on my current antenna: 8 × 30 meter radials. Using MININEC ground simplifies modelling of ground loss.

With this configuration the loss in the tower grounds is -0.7 db  and -1.0 db in the antenna ground, for a net gain of 1.4 dbi. The azimuth pattern is almost perfectly omni-directional. Improved tower grounds increase efficiency while the azimuth pattern becomes slightly asymmetric, with a broadside gain ~0.5 db better than in end fire. My towers are aligned approximately northeast towards Europe to facilitate wire yagis should I choose to do so at some future date.

With the electrical length increased to 55 meters the gain increases ~0.15 db as interaction decreases. This is negligible. The 2:1 SWR bandwidth in both cases is 100 kHz, without a matching network. With a better radial system the impedance would fall and require a simple L-network. However that does not change the SWR bandwidth.

This antenna is simpler and has somewhat better performance than my existing T-top wire vertical. All it requires is a catenary rope between the 40 meter levels of the towers. It would in actuality have to be at least 1 meter lower to avoid the rotation loops for the yagis on the 140 meter tower.

With sag in the centre of the span the true height would be around 36 to 37 meters, requiring a short capacitance hat suspended from the rope or dealt with at the feed point matching network. Gain loss for the slight length reduction is negligible. Were I to have a catenary rope to support a low band yagi it would be at a lower height and therefore require a longer capacitance hat for the 160 meter vertical.

Exploiting interactions

I am pleased that placing a wire vertical between the towers produces a better omni-directional pattern than with just the one tower. This is cause less by the symmetry of being between two towers than the increased distance (30 m) between antenna and tower. The base of my 160 meter antenna is only 20 meters from the 150' tower and the upper arm of the T-top gets to within ~10 meters. Modelling confirms the distance sensitive interaction.

With a 0.18λ spacing it is natural to think about a 3 element yagi switchable northeast and southwest, along with the omni-directional mode. It would require putting radials, switches and loading elements on the towers. For an antenna that requires the radials to be rolled up each spring that's a lot of work. Further, the antenna may preclude using the antennas on both towers while operating in yagi mode on 160 meters.

Is it worth it? Maybe. At the very least a model is justified to explore what is possible. Several decibels on top band can go a long way to improved contest scores. Implementation, if it occurs, won't happen until at least 2020. I have more than enough to do in 2019.