Wednesday, December 27, 2017

XM240 Update

Although I purchased my Cushcraft XM240 in 2015 it was only in use for the first half of 2016 when it was at a height of 21 meters. The antenna had been strengthened per (most of) the recommendations by Dave Leeson W6NL. It did well on 40 meters but with several negatives:
  • The cheap muffler clamps used on the aluminum channel element-to-boom clamp in lieu of the stock Cushcraft clamps did not work out. They could not prevent rotation of the elements on the boom in high winds. The thin steel saddles had little grip and if tightened further would only damage the boom.
  • The same was true of the muffler clamps used for the boom-to-mast clamp. At least boom rotation could be corrected by climbing the tower, which cannot be done for the element clamps.
  • Although tuned per the instructions (interpolated between the two lower settings) for the lower part of the band the antenna resonated ~7.125 MHz rather than the estimated 7.075 MHz. At 7 MHz the SWR rose to 3 requiring the use of a tuner, the risk of loss over long coax runs and undesirable extra steps for band changes and frequency excursions in the heat of a contest.
I set myself the goal of correcting these problems before raising it onto the new 150' tower. I was partly successful. With more time I could have done better, but in the larger plan this antenna's quirks were not highest priority. It was enough to get it working reasonably well even if not to the utmost possible for a small and compromised yagi such as this.

Boom-to-mast clamp

Please refer to the adjacent picture for the this and the next sections. This is a larger version of one published in an earlier article.

The previous owner's muffler clamps -- 2 for the boom and 4 for the mast -- were replaced. For the boom I substituted the two Cushcraft stock saddle clamps, originally intended to attach the stock boom clamp to a mast of up to 2.5" diameter.

They are snug on the 2.5" O.D. boom, but required reaming the holes on the custom ⅜" plate to make them fit. Ordinary muffler clamps do not follow any dimension standard, varying between suppliers despite being stamped with the same size, in this case 2.5". The Cushcraft clamps are truly 2.5" I.D.

Rather than 4 muffler clamps for attaching to the mast I used two DX Engineering saddle clamps. Twice the number of muffler clamps does not compensate for their poor strength under axial load. I carefully selected spots on the plate to drill the 4 holes for the mast clamps to minimize the risk of weakening the plate due to the multiplicity of holes already there.

Integrated truss support

In coordination with the new mast clamp holes mentioned above I utilized two existing holes on the large plate to bolt the aluminum angle stock for the integrated truss. This innovation is required since the truss extends above the tower mast.

The truss is set up and adjusted on the ground. Once up the tower I eyeballed the alignment and declared it good. I was wrong. Only later did I notice that the boom wasn't exactly horizontal. The error of ~2° downward is small enough that the performance impact is not significant. But it does look a bit odd from afar since the booms of the XM240 and TH6 are not quite parallel.

I suspect I made the error because at first the mast clamps were not fully tightened so that I could manoeuver the yagi. I snugged the clamps tight at the very end when my ground helpers had to leave, delaying lifting it up the mast. Apart from looking less than perfect I am not concerned about it. Very likely the antenna will come down next year and I can fix it then if necessary; when it goes back up it may not need the integrated truss support.

Element-to-boom clamps

To avoid weakening the aluminum channel used to support the elements with more holes I decided to revert to the stock Cushcraft boom clamps rather than use better quality saddle clamps. Installing them according to the manual was interesting in that it required a specific tightening sequence for the bottom, middle and top fasteners. Nevertheless I did it as prescribed.

The only omission was the boom truss which is supposed to attach to these clamps. I don't like the idea of a ¼" stainless steel bolt threads radially loaded so I continued with the custom boom clamps for the truss.

The Cushcraft clamps were a bit of an enigma. Despite following the manual and no matter how I fiddled with the alignment of bolt holes in the clamp and the element channel it was impossible to make the elements perfectly square with the boom. Although I did the best I could the elements are not as parallel to each other as they ought to be. The error is small enough to be of little importance to performance, yet it is aggravating. Whether the error is mine -- I don't see how this can be true -- or that of Cushcraft/MFJ quality control is difficult to say.

Another quirk, though not one attributable to Cushcraft, is that with the stock boom clamps for the elements the elements are not in the same plane. When one element is horizontal the other is not. This is due to the machining of the custom boom insert. This is not an issue for muffler clamps securing the elements to the boom since the elements can be rotated to make the elements co-planar. Again, the error is small and not a hindrance to performance.

Tuning adjustment

The tuning challenge is this: decrease the SWR in the CW segment of 40 meters without changing the gain and F/B curves. From experience using the XM240 the positioning of the F/B and gain curves are where I want to keep them, providing acceptable performance between 7.0 MHz and 7.2 MHz. Two element yagis, especially those with shortened elements have narrow optimum bandwidths for gain and F/B so you don't want to mess with those metrics if they are already correct.

Why the feed point impedance differs from what the manual promises is not clear to me. One other contester I've spoken to noticed the same behaviour. He deals with it in the shack by adjusting the match on his tube amplifiers. Modelling isn't an option to fully investigate the antenna's performance since NEC2 is inadequate and NEC4 is not an investment I am willing to make.

All is not doom and gloom since there is another way to get what I want without extreme effort. The method relies on understanding how yagis do what they do. In particular that the gain and pattern, and their associated electrical parameters are unaffected by modest changes to the driven element. By modest I mean with respect to the element's physical dimensions and matching network, if any, at the feed point. Changes to parasitic elements are another matter entirely, and must not be touched for the following procedure to work.

Since this antenna has no matching network -- only a common mode choke -- and I want to keep this simple I am constrained to making changes to the length of the driven element, in particular the tubes serving as the elements tips.

Although NEC2 cannot be accurate for this antenna I created a proxy model a couple of years ago to investigate aspects of the antenna that interested me. The model uses constant diameter elements and therefore makes no allowance for reactance errors due to the tubing taper schedule -- Leeson's stepped diameter correction in EZNEC does not support loads (coils in this case) or capacity hats. The resulting model is frequency shifted downward and likely alters the pattern and impedance a small amount. Even so it is good enough for what I had in mind.

In the second of the two proxy model SWR curves each half of the driven element has been extended 5 cm (2"). This moved resonance down 50 kHz without changing the frequency range of the pattern. Ignoring the inaccurate frequencies calculated by NEC2 it is the amount of downward shift that is of interest since the actual antenna will do the same. Just imagine, if you will, that the lowest SWR shifted from 7.125 MHz to 7.075 MHz.

You might guess that we could push the matter further if CW is of utmost importance. That would be wrong. While a subtle difference notice the reduction of 2:1 SWR bandwidth below resonance from ~105 kHz to ~85 kHz. The reason is that radiation resistance drops sharply near maximum gain, which for a 2-element yagi with a reflector is below resonance. Further lengthening of the driven element reduces the SWR bandwidth and increases the minimum SWR.

Out of some concern with the reliability of my proxy model I extended the halves of the driven element 1.5" (3.7 cm) a little less than the modelled 2" (5 cm). Once up the tower I measured the SWR with my analyzer and saw that the minimum SWR was 1.1 at 7.085 MHz and the SWR at 7.0 MHz was 2.0. With some relief I declared the mission accomplished.

Back in the shack the frequency of minimum SWR shifted upward to 7.1 MHz while the SWR at 7.0 MHz stayed at 2.0. This is not surprising since used 50 Ω coax is rarely 50 Ω, and such is the case for the 330' (100 m) of LDF5-50A tested and used to feed the XM240. The effect of impedance variation is more noticable at low SWR than at higher SWR. If you think about it for a few moments I think you'll see why.

Tram experience

The XM240 is the heaviest antenna I've trammed up a tower, coming in at ~75 lb, or 10 lb heavier than the stock antenna due to the W6NL designed mechanical improvements. It looks pretty nice in the picture I posted earlier. The reality was not quite so wonderful.

My lawn tractor was not entirely up to the task of tensioning the tram line with the heavier antenna. Some sag is normal on the line even with high tension since the weight of the antenna is concentrated at a single point by the pulley. The lack of adequate tension became noticable as the antenna approached the tower.

Sag at the upper end of the tram line meant that the angle of the antenna's motion gradually shifted towards the vertical. My friends on the haul rope experienced this as an increased effort to move the antenna due to loss of mechanical advantage.

That was a minor problem compared to the changed orientation of the yagi. With the haul rope angle becoming increasingly vertical the element tips rotated upward. That made my job on the tower more difficult as I struggled to rotate the boom so that the mast clamps could be installed.

Next time I'll consider using a fixed anchor for the tram line and a winch so that tension will not be limited by the small tractor's traction and weight. I nixed the offer from one of my friends to use his car since the valuable vehicle is at risk of body damage should the antenna swing just a small amount as it lifts off the ground. The elements of a 40 meter yagi are long!

LCA performance update

Soon after acquiring the antenna I began looking into the performance of the element loading coils. There was a story going around that the coil Q was ridiculously low, coming in at under 100. If true the loss would be excessive. I wondered if it would be worthwhile to replace the Cushcraft LCA (4 of them) with a high Q home brew replacement.

Based on my own inspection of the coils I determined that the low Q assessment could not be true. This is because the fibreglass form is hollow not solid as assumed in the one ham's calculation. I estimated the Q to be closer to 200, and therefore with a loss less than -1 db. Earlier this year I received an email from Bernard F6BKD describing his measurement of the LCA with an HP Q meter and got a value of ~200. Now I have the data to believe the coil loss is no worse than in my model.

This is still not ideal. I can live with it until I replace the XM240 with a higher performance yagi (or two) for 40 meters or upgrade it to a W6NL Moxon, thus eliminating the LCA entirely. For now it continues with its stock electrical design. However I did was wrap the coil anchor screws with cable ties since the self-tapping screws are reported to loosen over the years.

Isolated reflector element is still isolated

Both elements of the XM240 are electrically isolated from the boom. Many owners of the XM240 short the reflector element to the boom claiming that it reduces noise -- by draining static buildup on the element -- and adds to the top loading when shunt feeding the tower on 160 meters.

I didn't do this because, quite frankly, I forgot. I have since had instances of static QRN on 40 meters with the XM240 and not on the inverted vee during rain and snow showers. This may indicate that I should have shorted the reflector. The matter is more complicated than that and there are other possible explanations for the observed static. Next time the antenna comes down I'll rectify the problem, just in case.

The future

I haven't yet said how the antenna performs at its new height of 47 meters above ground. That will come in a later article on how all the antennas play. For now I'll only say that it does very well.

Over the winter I will rethink my long term plans for 40 meter high performance antennas. Due to the mechanical challenge I am not yet ready to tackle a full size 3-element yagi on 40 meters. The tower and rotator are up to challenge so it is not out of the question that I'll follow that route. What I can say is that I remain unsatisfied with the performance of 2-element yagis since the gain, F/B and SWR bandwidths are narrow.

The W6NL Moxon conversion of the XM240, or the alternative built from scratch solves the F/B and SWR problems but not the gain. That will require another element. Despite this I remain impressed at what Dave Leeson has accomplished with the XM240 conversion and the performance objectives he met in the design. Many hams have done the conversion and are very pleased with the result

There will be more to report on this subject in the coming months. In the meantime there are many other antenna projects of higher priority. I am well set on 40 meters for the next months with the XM240 as it is and complemented with the inverted vee lower down the tower.

Friday, December 22, 2017

Winter Closes In

Antennas and feed lines on the 150' tower were finished just in time. Since then the weather has turned very cold and snowy. Several winter projects have had to be delayed, and some are likely to be cancelled. Temperatures have plummetted far below normal for even this climate, with frost penetrating the ground sooner than expected. The weather forecast shows no relief until at least the beginning of January. Work in this weather is uncomfortable and unsafe.

One important job that I had to put off was to rent a trench digging machine. It is now very likely that feed lines and cables to the big tower and in other areas will have to stay above ground until spring. The machine does not handle snow very well and there is a potential for mishaps due to freezing in the top level of soil.

This is not so bad were it not for the deer. I worry that they'll step on the Heliax. So far the few I've seen have stayed on the other side of the tower. I am fortunate that they haven't tangled their hooves in the 160 meter antenna radials.

Winter antenna projects

80 meter array base
I have begun work on the 80 meter vertical array. Now progress is stalled due to the weather. Working fast when the temperature happened to rise above freezing I planted the base for the driven element (tower) and the three screw-in guy anchors. When (if) the weather moderates I'll get back to work on it. My minimum objective this winter is to have it working as a simple omni-directional vertical.

The array has been redesigned from what I originally intended for a variety of practical reasons. Once the model has stabilized I'll write an article on it, following by another on the actual construction. Indications are that I can achieve improved performance, and better assess how it compares against the more commonly-used 4-square array.

Additional Beverage antennas for the low bands have been roughly surveyed. There are numerous practical considerations on their placement, topology and switching which I am gradually working through, along with research on how others have addressed similar issues. I hope to make progress on all of these over the winter, though that is difficult to plan at this point. Weather determines the pace of outwork work for the next few months.

Moving indoors

There are many projects I have planned and can do indoors over the winter. Building a competitive station is more than towers and antennas. Here are a few I have on my plan.
  • Fully integrate the FTdx5000 with the PC. With the ancient laptop gone I expect few difficulties connecting the SCU17 interface to get audio, spectrum and CAT from a single USB connection. With this in hand there is more I can do with contest software and to experiment with digital modes.
  • Arduino kit to prototype station control hardware and software. My first project will be a direction indicator for the prop pitch rotator, followed by much more. Some of this will be purely experimental, with only the most useful devices promoted to actual equipment. I want more automation and software control in my contest station. The choice of prototyping technology does not dictate that the final version will be Arduino.
  • SO2R and multi-op contesting requires a variety of audio, switching and rig control systems. Most I do not yet have. Winter is an excellent time to review options and experiment.
  • Ergonomics at my operating position leave much to be desired. I am experimenting with different arrangements of rigs, computer, chair, desk and accessories to make operating more pleasurable and contests more endurable.
Articles on these will follow as and when they significantly progress. I also intend to experiment with other things such as digital modes, if only to play around and see what others are getting excited about. Although I don't expect to become a digital modes enthusiast the technology intrigues me. Perhaps this is because I have experience developing DSP software and coming up with tactics for dealing with poor SNR.

Garage workshop
LR20 jig and some of the stored cable

With more of my store of tower, cable and related hardware installed out in the field there is more room in my garage workshop. Amazingly I still have well over 1,000' of Heliax and perhaps 200' of large diameter aluminum tubing and pipe in there!

The unheated garage is not terribly comfortable for winter work. The thermometer on the back wall reads -10° C, and it's only 2° colder outside. On the other hand there's no wind chill. Despite the conditions in there I am arranging the space to permit a few construction projects to proceed over the winter.

One example is a section of LR20 tower that I picked up this fall. It will serve as a jig for construction of side mount hardware and other attachments for the 150' tower. This is far more convenient and safer than working on the actual tower. Unlike self-supporting tapered towers every LR20 section is essentially identical.

Immediate concerns

Ever since I moved in I have been tracking down noise sources to ensure the best possible receive conditions. The problem is not acute for the present but could be once I return to QRO operating and have to deal with many more weak replies during contests.

Despite being far from neighbours I am not free from noise. Some of it comes from within my own house. One persistent problem is noise from the many computers, interconnect cables and unshielded Cat5e cable to the terrestrial wireless antenna that is my sole source of internet access. The noise is greatly reduced for the antennas on the big tower since they're farther from the house.

Then there's this:

Depending on the weather power line noise in the southwest direction can be S9 on the high bands through 6 meters. The noise blanker can mostly deal with it though not without distortion when signals are present, and inter-modulation under contest conditions. There are a couple of power line noise sources in a couple of other directions that are not problems since they appear to be quite far away.

The local utility has come by to discuss the issue and plans to return in January to track it down. They have been very responsive and appear interested in getting it fixed. As is often the case it can be difficult to resolve since the noise appearance is not sufficiently predictable and the utility works to a schedule. If all else fails I'll rig up a portable sniffer so that I can help locate the source. It helps being in a sparsely populated rural area where the number of potential sources is small.

Aside from noise I am beginning to fret about what antennas to put up next year. This will require careful planning before I can begin design and construction. My ongoing experience with the antennas I have is proving very helpful to determining where the need is greatest. I plan an article to report on how the current complement of antennas is playing.

2018 planning

Come January I will make an attempt to finalize my station construction plans for 2018. Many yagis are certain to be in my construction plan, and one more big tower is possible. I'll try to be more realistic in my objectives than I was for 2017. It's the dependencies on weather and assistance that most imperil any plans I can come up with since those are often outside my control.

Expect an article later in January as I do my traditional of the year that was and look forward to the coming year. In this climate winter serves as a bookend to both seasons.

Enjoy the holidays wherever you are. From today onward the days get longer in the northern hemisphere so spring can't be too far off. As time permits expect at least one more article before year end.

Saturday, December 16, 2017

Concise Reviews of Parts and Accessories I've Used

With all the construction work I've done on my station this year I have gained some wanted, and unwanted experience with a variety of products. Rather than keep it all to myself I will give a concise review of several of these. Almost all are brand specific, with a couple of exceptions.

Since my experience with these and competing products is limited don't solely rely on what I have to say. Look around and you'll find other, perhaps better products and other opinions. Be sure that the reviews you listen to are informed by actual use, preferably over the long term.

Cable ties

Let's get one stinker out of the way. Over the years cable tie quality has improved quite a lot, especially those most common in the retail market. Countless cable ties litter my antenna farm to hold thousands of feet of all types of cable, near the ground and on the tower. Many work well, but there are exceptions.

One to avoid
Strolling down the electrical aisle of a well known big box store I noticed the rack of cable ties. Since I go through so many I grabbed a couple of packages of an unfamiliar brand, though reasonably confident by the description and the store's generally favourable reputation. It didn't work out.

Out of a package of 100 I used 80 of them on a recent climb to attach cables to my big tower. The failure rate was ~20%. Yes, really. The ones that survived installation are still there (I hope) and will require periodic inspection to determine whether they must be replaced. Here are the ways they failed on a cloudy day with a temperature of -1° C:
  • Break at a right angle bend around steel tower legs. Other brands never did this under the moderate tension applied while tightening the cable tie.
  • Torn strap during handling or when pulling on the free end to tighten it.
  • Failed tooth in the ratchet box.
Despite one bad brand be careful not to dismiss unknown brands. I have had good success with black cable ties manufactured close to home or in Asia, and even house brands of reputable stores. Since this is a new station the cable ties have at most survived one full cycle of seasons. I am not yet confident enough to recommend a specific product. But as you can see there is one I can warn against.

DX Engineering U-clamps

Earlier this fall I ordered a variety of DXE saddle clamps and Cycle 24 galvanized muffler-style clamps from DX Engineering. I used 3" saddle clamps (both 5/16" and ⅜" bolts sizes) in the modified boom-to-mast clamps for the TH6 and XM240 to attach to the 2.875" mast turned by the prop pitch motor. The Cycle 24 clamps I've used everywhere from boom trusses to mast steps and as mechanical aids for tram lines anchors and to hang pulleys for heavy lifts.

Aside from one incidence of user error (that's me) that galled one of the stainless steel u-bolts I am very satisfied with both products. They're easy to use, quality appears excellent and they have excellent holding strength in comparison to common galvanized muffler clamps. The winds have been blowing hard on top of the big tower, the temperatures have plummetted and neither yagi has budged.

The only complaint I have is that the stainless flat washers that come with the saddle clamps are thin and weak. They distort easily, and especially if the clamp surface isn't perfectly flat. I had this occur on the TH6 boom splice and mast clamp where there is a narrow flat surface on the inner side. The difficulty was resolved by removing the flat washers. The lock washer now sits directly on the aluminum surface.

The Cycle 24 clamps that I used and reused several times have not distorted due to asymmetrical loads and the galvanizing remains intact. Bolt threads have withstood heavy leaning on the nuts with a big wrench. They're inexpensive and I keep a few in my toolbox for odd jobs.

Hamplus AS82N

Shown with weatherproofing incomplete
A 2x8 antenna switch walked up to me at a gathering of contesters and asked me to buy it. I did. Well, that's almost true except the walking and talking was done by the device's owner. Hamplus has a good reputation and the price was right so I bought it, thus advancing one part of my station automation plans for SO2R and multi-op.

It's designed for outdoor and indoor use. I wanted it outdoors so that's where it went. With a few lengths of pressure treated lumber and a handful of hardware I affixed it to the side of the Trylon tower under a simple weather cover. It is now working just fine along with the manual control unit I built for it. Putting it outdoors reduces the mess of coax coming into the house, yet is readily accessible for maintenance.

So far it is working well. It has one flaw that prevents selection of one of the antennas from one of the two sides. I don't know if the short of adjacent lines from the connector is that way from the factory or due to abuse. Unfortunately the fault is on the underside of the board which can only be accessed by removing a multitude of almost inaccessible fasteners securing the 10 SO239 jacks to the chassis. This is very annoying. I haven't made the attempt as yet and perhaps I never will. So for now it's a 1x8 + 1x7 switch.

Also annoying is the skimpy and inadequate documentation at their web site. There one can find the pin out for the DE25 connectors but not how the switching is to be accomplished. That is, to select an antenna is the pin grounded or powered? Of course if you use their controllers you don't have to know, but that is not what many contesters do, opting for custom hardware or software control. A conversation with the seller (who also didn't use a Hamplus controller) eventually resolved the issue: ground the pin to select that antenna.

Nice switch, unpardonably poor documentation. Worse, the AS82N isn't documented at all so I had to rely on a similar product and compare that with what I found under the hood.

Splicing tape

The more expensive your cable and equipment the more important it is to protect them against the elements. Don't skimp! This is not the place to save a few dollars when it comes to protecting low loss, expensive coax and outdoor electronics for switching and control. Do it right. Cheap vinyl tape has its place in the great outdoors but not to seal a connection that must not leak or allow incursion of damp air (condensation and corrosion).

I have nothing unique to offer in this regard since many have already said it. Yet too many hams don't listen. You decide.

Left to right: inexpensive Scotch; no-name self-vulcanizing; Temflex rubber splicing; good Scotch outer layer
Use a sealing tape around every joint, whether fixed (e.g. coax entry at back of connector) or movable (e.g. male coax connector head). Don't rely, for example, on the rubber gaskets found in N and Heliax connectors to protect you. Assume that every inadequately protected joint will fill with water, moist air or pollutants. Over months and years it will certainly happen.

In larger gaps I use an underlayer of Coax-Seal (not shown). I protected the back of every Heliax connector with this additional layer. I avoid Coax-Seal on the connector ends since it can become gooey and difficult to remove when disassembled years later.

Temflex rubber tape (third from left) can be difficult to wrap but appears to work well. I bought this roll from DX Engineering but it or similar products are available where electrical supplies are sold. It sticks together by self-adhesive rather than an adhesive coating. I have a similar product from another major brand that I have not yet used and so cannot yet compare to Temflex.

The self-vulcanizing tape (second from left) is thin and stretchable, and is easier to handle than the Temflex. I have yet to have a seal fail with this type of tape. Be careful not to overstretch or tear it. I've used both this and the Temflex in freezing temperatures without problems.

On the left is a good quality name brand inexpensive vinyl tape. If you do use it try to avoid using this or (often lower quality) no name or house brand tapes as the outer layer. Few can withstand years of exposure. The worst have such poor adhesive or flexibility that it will soon unwrap on its own. The Scotch 33+ or Scotch 88 makes an excellent outer layer.

The better tapes are available in wider widths from commercial suppliers. This makes wrapping and protection much easier. Old Heliax connectors I've scrounged that are covered with wide tape are clean and dry after years of exposure.

Rotator grease

When I refurbished a heavily corroded Hy-Gain Tailtwister rotator (T2X) last year I switched to synthetic grease. Unlike any petroleum based grease I've used the rotator turns as easily at -20° C as it does at +20° C. I'm sold. We'll have to see how it performs over longer periods.

I have no particular brand or type to recommend. Look around in any auto parts store and you'll find many varieties. Although synthetic grease can be expensive you don't need a lot and it comes in small packages.

Heliax connectors

When it comes to expensive Heliax connectors sometimes beggars can't be choosers. If you do have a choice I recommend the modern single-piece connectors over the two-piece connectors. Below you see a selection of both types.

On the left are used two-piece connectors for LDF5 and LDF4. Particularly annoying are the centre pins of the LDF4 two-piece connectors which are soldered onto the solid centre conductor. It's difficult, hot and messy work that is also hard on the foam dielectric. I've done many of these years past and I hated every moment. LDF5 two-piece connectors are much easier to put on since the centre conductor screws into the hollow centre conductor.

One-piece connectors are much easier once you get the hang of the technique. New ones come pre-greased and the best require you to simply trim the jacket, cut the outer conductor and foam at a right angle on a corrugation ridge and cut the centre conductor to a precise length. That done the connector slips straight on and you tighten with two wrenches. It's the same procedure on all the connectors shown: LDF4 N-male, LDF5 DIN-female and LDF7 DIN-female.

Windows 10

Avoid if at all possible. If you cannot avoid it on your shack PC you will soon curse the jackasses in Redmond. Here are some of problems you should expect to deal with:
  • Peppering you with advertising and installation of unwanted software applications.
  • Automatic restarts (surprise!) in the middle of a contest (or rag chew) to apply urgent (?) updates.
  • Gives software update downloads highest priority, making your other uses of the internet (e.g. spots and RBN) slow to a crawl.
  • Occasionally replace proper device drivers with the wrong ones after updates.
  • Shuffle the COM port numbers after some major updates.
  • Intrusive windows that pop up and demand your attention and action when you're running Europe at 5 QSOs per minute.
There are cures available for most or possibly all the problems, but what a hassle. I think I've got my new shack PC suitably configured, for now at least. For example, while I was typing this article I heard a click and turned around to notice that the shack PC had shut down all my applications (including my logging program and Telnet connection to monitor 160 meter activity), started applying updates (of unknown type) and then did a restart.

I think I now have that problem solved. At least I hope so.

Unless you are willing to do go through some aggravation to research and apply fixes, including some that are quite arcane, I recommend sticking with Windows 7. Apple and Linux are not viable alternatives for many of us since most ham software is Windows only.

Tuesday, December 12, 2017

Topping the 150' Tower

At long last the big tower project is substantially complete. By "substantially" I mean that a few small tasks remain although all the antennas are in use and rotating as they should. This project has taken quite a bit longer than I anticipated or planned for so not everything planned has been accomplished. Even so I am pleased (and relieved) to have achieved this milestone.

In an earlier article I described getting to the point of having the tower complete. Now I'll talk about the process to make it operational; that is, with working antennas. One disappointment is that I was unable to light up the top yagis in time for the CQ WW CW contest.

Time pressure

As the saying goes: time waits for no man. Back in August I was feeling pressured by the approaching winter when major tower and antenna work is out of the question. Even with this foreknowledge I failed to do all that I wanted.

My primary constraint was people. A lot of manpower goes into this size of project. You can either hire people or rely on friends. As the ham population ages the ability to solicit help declines, and many who are enthusiastic and willing are not physically able to do so. Hiring professionals is no panacea since everything must be prepared in advance and any mistakes or gaps will result in substantial additional costs.

Ultimately I ended up relying on myself and on friends. You can never have too many friends! Cherish them and return the favour of their assistance.

Antenna complement

With the calendar inexorably advancing I shelved plans for yagi construction and went with what I had on hand. Those yagis and a couple of wire antennas to give me the required coverage for effective contesting and DXing are what I have for this winter season.
  • Cushcraft XM240 at 47 meters: I made a few changes to the antenna since it was on the Trylon tower earlier this year. I'll cover this in a separate article.
  • Hy-Gain TH6 at 44 meters: With no time to spare I put this ancient antenna up top for low angle, longer path DX on the high bands. The antenna was refurbished, including trap repair, new trap covers and replacement of the Hy-Gain balun with one from Balun Designs.
  • Hy-Gain Explorer 14 at 34 meters: The antenna is fixed on Europe. It works well enough for a short boom tri-band yagi, though it is not what I had in mind. Next year it will be replaced by a more suitable set of yagis for the important European path.
  • Fan inverted vee for 40 and 80 meters with apex at 32 meters: The 80 meter vertical array is a winter project and there was no time to build a wire or tubing yagi for 40 midway up the tower. This is my solution for the winter, after which I plan to remove it to make room for a more permanent high performance solution for 40 and 80 meters.
  • T-top vertical for 160 meters: The antenna is simple and surprisingly effective with only 8 radials. If I'd known how well it worked I would have planned a more serious effort in the ARRL 160 meter contest. Now I am looking forward more cheerfully to upcoming contests. This is a winter antenna that will be taken down in the spring. I don't yet know if I'll put it up again next autumn.

XM240 in flight, with integrated boom truss I've been so busy and the bands less than stellar that I have not yet had opportunity to thoroughly test the antennas, especially on bands where I now have two or three choices. There are some expected behaviours and some that were unexpected. This is a subject for a future article.

The prop pitch motor is working well so far. I attached the direction indicator potentiometer on my final tower climb and it will be wired up to the shack controller shortly.

Tram line, again

Raising the TH6 and XM240 with a tram line was similar to how the Explorer 14 was raised. The important differences were the greater weights of the yagis, larger size and top attachment to the mast rather than the tower. These all require changes to the procedure.

First, the ground anchor must be moved further out from the tower so that the tram line angle is similar or even lower to maintain or improve, respectively, the mechanical advantage. I had 300' feet of steel cable on the reel and I used it all. I was close enough to a small forest area that I considered using a tree for an anchor rather than my lawn tractor. That would have required a winch to set the tension, which in the time available was an undesirable complication. As it was we were challenged by the autumn dampness which reduced the tractor's traction in the hay field. It needed manual assistance to set the tram line tension.

Hauling yagis up the tram line
Rigging the antennas for balance and centering required more care due to the greater sizes of the yagis. This was the most time consuming part of the procedure. The XM240 has the added complication of attaching the fragile capacity hats after the antenna is off the ground. Since the yagis were substantially heavier there were two people on the haul rope.

The XM240 was lifted low on the mast and raised afterwards to the top. There is a substantial bending moment on the mast which would require a back stay to make the tram line mechanically sound. I chose to keep it simple and not use a back stay. Once the XM240 was on the mast and tested with an antenna analyzer I climbed the mast to install a pulley at the top and thread another rope through it.

When my crew returned the following week I tied the haul rope to the mast rope and with their muscle I lifted the yagi to the top of the mast. In comparison lifting the TH6 immediately afterwards was straight forward.

Fixing problems

As you might expect not everything went according to plan. One of the stainless steel saddle clamps was damaged while fighting the TH6 into horizontal orientation. The threads were greased and (although I know better) I compensated for incorrect position with extra torque on the wrench. The threads galled. A few days later I went up with another clamp and a tap to either replace or repair the u-bolt threads. I was able to save the clamp quite easily by chasing the threads.

The TH6 boom truss turnbuckles were threaded a few turns and taped to the boom. A turnbuckle and one of its screws unwound itself and fell off. They somehow survived the 150' fall without any visible damage and with the threads intact. After cleaning the boom truss was completed a few days later. The less on to secure turnbuckles and their screws better for the lift.

After the yagis were up for about a week I went up to do some work and got a surprise. One of the shims between the lower and upper masts worked itself loose, moving upward and falling to the bearing plate.

I put it back and found that it fit loosely. The next time up the tower I brought along a muffler clamp to hold down the shims so this wouldn't recur. This is a good reminder that the lateral force on the mast due to wind on the yagis is substantial. I was not surprised that the shims would gradually deform under the force to match the mast curvature, but the way that shim got pushed out of the splice was a surprise. Perhaps next year I'll revisit the shims.

Lifting coax and cable

Coax and wire cables are surprisingly heavy when measuring 130' (40 m). They are not so heavy that lifting is difficult, the concern is that the cable will be damaged when hanging by its own weight. Even LMR400 must be treated with care. LDF5-50A Heliax (⅞") requires special measures.

I cleared one of the tower faces of obstacles to clear the way for the lift and ensure the Heliax would not encounter any sharp bends. Due to the position of the side mount brackets and the need to avoid the climbing face this left exactly one choice. Unfortunately that side held the large drive unit for the prop pitch motor at the 140' level.

I mounted the pulley immediately below the drive unit. The Heliax would pass through one strut and terminate just below the top of the tower's north side, and there attach to the rotation loops. To accomplish this Heliax was lifted from a point 10' to 12 ' below the top. The rope is taped at intervals above that to protect the cable from interference and damage. The N-connector is covered with a cap designed for this purpose.

Andrew sells cable hoists that wrap around the Heliax and distribute the load equally around the circumference over several inches of cable length. I don't have one. Rope can be used to achieve the same requirement with a coil of many turns, wrapping the end so that the rope can't unwind and ensuring that all knots and bends are on the outside of the coil. After each lift I inspected the cable to ensure there was no damage, not even scuff marks or scrapes on the jacket.

The cable threads between the Explorer 14 boom and tower. This was accomplished without duress. When the cable approached the pulley I climbed the tower. There I removed the tape wraps one at a time from the top as my helper on the ground lifted the cable in short steps. Once in position I spliced it to rotation loops and worked my way down the tower securing the cable at every tower diagonal. If you use the Andrew mounts (expensive) you can get away with intervals up to 5' or 6' depending on wind and ice loading.

For major installations such as this I strongly recommend mechanical and electrical tests of every section of feed line once the connectors are attached. At the very least use an antenna analyzer and a dummy load to check that the impedance or return loss is as it ought to be across the widest possible frequency range. Once it's installed and a problem is discovered it is very difficult to isolate and deal with. Don't take shortcuts. I also recommend using the best quality products to protect connectors and splices from the weather.

Cable on the ground

Temporary overground cable runs
Each run of feed line is in two sections: Heliax from the switch box near the house to the tower; LMR400 or Heliax up the tower to the antenna. I acquired numerous 100'+ lengths of LMR400 as reel ends from a local supplier at a discount for this purpose.

Since the side mount antennas (Explorer 14 to Europe and 40/80 inverted vee) are temporary I used the full lengths of LMR400 and coiled up the extra. I preferred this to cutting the cable to length to "future proof" to avoid the risk of waste when it is redeployed.

As I type this the cables cross the open hay field above ground. Digging a trench and burying them had to be deferred, on advice of the renter, because the trencher would cause clumping of the half-frozen soil, freeze when exposed and then not settle properly when the soil is pushed back in. I may yet get this done before Christmas once the weather rises above freezing. In the yard I expect to have an aerial run for the cable since burial would encounter too many obstacles.

Not yet tidied up

The 2x8 antenna switch is installed at the base of the Trylon (70' tower). This proved to be a convenient termination point for the many coax runs, including those on the Trylon itself. This unit has all the connectors on the bottom, making it easy to build a weather cover. The tower provides support for the housing and cable terminations. Heliax cables are terminated with jumpers to the switch box to avoid having to contort the Heliax and to make it easy to transition from N to UHF.

There are two runs of LMR400 to the shack, plus existing runs for non-contesting antennas. Managing cables this way is much easier than terminating everything indoors and grounds inactive antennas well away from the house. I believe this is a good trade off with having to install and maintain switching boxes outdoors. It will only grow more complex as I add more antennas to my antenna farm.

I'll have more to say about switching in a future article. It can get complicated.

Finishing and clean up

As I descended the tower the final time after installing the last Heliax run and attaching the direction indicator for the prop pitch motor I stripped off the tower what was left of the rigging. This was little more than a pulley and the 100 meter long haul rope.

Short path to east Asia on 40 through 10 meters
While I finished attaching the Heliax to the tower my helper coiled the rope and cleaned up the area around the tower. We left everything tidy. All the cables were given one final test, final splices sealed and all tools and material carted off and stored. I even swept the garage clean.

With that and some on air testing of the antennas the tower project was declared complete. Of course there will be much more to come next year, but this is nevertheless a major milestone. I am very happy with how far I've come and the obstacles overcome.


Winter projects have already begun. The base is in for the 80 meter vertical array and the new PC is configured for contests. Yet there is much more in my plan.

How far I go this winter will depend on the weather and my inclination. Some rest and relaxation is planned, or at least turning to non-ham projects and activities long put off.

I committed to give a February talk to local contesters and DXers on the subject of building my new station. That should be fun.

Right now the snow if falling and the north wind blowing. This is a good time to switch on the radio to use and enjoy what I've built. That's what this is all about.

Wednesday, December 6, 2017

Dog Days of December

For many people in this wintry climate, myself included, the closing weeks of autumn can be a time of low energy. It is brought on by the lack of sunlight, rapidly worsening weather and, perhaps, the excess commercialism in advance of the holiday season. As a ham at this point in the solar cycle there is less refuge in the shack since the openings are short and often fail to coincide with our busy schedules.

Yet there are contests aplenty, and still tasks to be done before the big tower project is finished. In between there is operating to be done and fitting in the rest of life. Despite some inevitable lassitude and exhaustion I'm keeping busy. All that said, let me briefly take you through the things that are not helping my mood this dark, cold December.

DXpedition lull

There was a great flurry of DXpeditions in November. Most of those are now done, many having been trips to operate CQ WW CW from a rare multiplier country. There is the usual potpourri of DX on the bands, though not quite as much to cause excitement. That said I did get a thrill catching a not-a-DXpedition 7Q7 on 40 meters.

The excitement will return in January with quite a few DXpeditions planned to very rare and moderately rare entities. That, the deep cold of winter and increased sunlight are sure to spark my enthusiasm.

CQ WW CW is past

CQ WW is unquestionably the highlight of the annual contest calendar. Now they're done. There is an inevitable letdown in the immediate aftermath. I expect the excitement to return once we get closer to the ARRL DX events early in 2018.

I put in a modest effort in the ARRL 160 meter contest last weekend, more to try out my new 160 meter antenna and new equipment within the shack. My expectations should not have been as low as they were since the antenna works surprisingly well. In retrospect I should have operate more hours than I did.

I finally got the new contest computer set up which is a tremendous improvement over the ancient Vista laptop I used in the shack since returning to the air in 2013. My antenna switching system also works well despite being entirely manual. I am getting ever closer to SO2R.

Low band challenges

Low band aficionados love QRN-free winters and the bottom of the solar cycle. It is certainly true that 80 and 160 meters light up with activity and even throw some juicy DX our way. On the downside is that even when conditions are good the low bands are a challenge.

Constantly digging signals out of the noise is fatiguing. Timing sunrise and sunset openings to the far side of the world, while exciting, is disruptive to one's life and sleep pattern. It takes getting used to. Yet what can one do when the MUF to anywhere interesting drops below 7 MHz mid-evening. It's the low bands or nothing.

6 meters

There is a winter solstice sporadic E (Es) season. Unfortunately it is far less intense than the summer Es season. I've listened a bit to the activity when I see spots on the cluster but have yet to transmit. Working the same old stations motivates me very little.

Winter projects

There are many antenna projects that can be done in the coldest months. Last winter I put up my northeast Beverage in February. This year I want to add Beverages for other directions. I also plan to begin construction of a directional 80 meter array. Lots of planning has been done and the north field has been surveyed with the placement of the tower (driven element) and parasitic wire elements.

Despite the long list of winter antenna projects working outdoors in the snow and the wind is not all that pleasant. Although I enjoy winters and being active there is a significant difference between, say, snowshoeing, and antenna work. In one you're constantly on the move generating body heat, while in the other you quickly chill while moving slowly and doing detail work that must often be done with bare hands.

The trick is to alternate indoor and outdoor work to keep it from becoming a miserable grind. It also takes a few weeks to psyche myself to take the plunge to get out there and get it done. That means January. On the bright side there are no black flies or mosquitoes.


Despite my long list of woes there will indeed be a great deal of activity this winter. As I write this the big tower project is several day effort to completion, weather permitting. It will be nice to enjoy the fruits of my labour (and that of many friends) over the winter months. You will see a few articles coming up on topping the tower and discussing how the various antennas play.

Work inside the shack will continue apace. I intend to become SO2R and low-power multi-op capable before spring arrives. Additional work for the future will add the switching and filtering for high power, and more automation. You can get away with little filtering and other things when you stick to 100 watts in the contests.

My 2018 plan remains sketchy at present. I will return to this topic in January.

Tuesday, November 28, 2017

CQ WW CW: The Good and the Bad

CQ WW is arguably the biggest event on the contest calendar. My station was in poor shape for the SSB contest at the end of October and I hoped I'd have everything ready in time for the CW contest this past weekend. I didn't quite get there despite a big push in the final hours preceding the start of the contest on (our) Friday evening.

The most glaring hole in my station is that I was unable to run coax up to the yagis atop the big tower. You can see in the picture that they are up there sitting pretty, tuned and rotating, serving only to tease me. I ran out of time. At the last moment I had to choose between putting up a 40/80 inverted vee or one Heliax run. With nothing else for 80 meters I opted for the inverted vee.

In a way I'm complaining about nothing of importance. It's just that I know how much better I could have done had I completed the antenna work. As claimed score reports flood into 3830 it's clear that I did very well in comparison to others in my class and geographical region -- Single-op; All bands; Low power. Something worse happened to a local big gun who suffered a concussion that ultimately took him out of contention. I could only offer sympathy when we spoke before the contest. Health is more important than anything.

What follows is a detailed breakdown of my experience with the station as it was this weekend and what I learned. That will inform my future plans. I kept a notepad within reach with which to take notes so that I wouldn't forget. Items of significant importance I will delve into in future articles.

So sleepy

The rush of tower and antenna work left me exhausted. Climbing and working on towers is physically demanding, even more so in cold weather. When I sat down at the radio after the evening meal to configure the logging software and test the antenna switching I nearly fell asleep.

I made it through the first evening on caffeine. Since I needed sleep I missed the start of the 20 meter band opening Saturday morning. I didn't feel truly rested until Tuesday.


I put off buying a computer until the big sales immediately before the contest. The computer was already selected but deferred for the discount I was told was coming. Unfortunately it was out of stock when I did make the purchase on Thursday so I could only leave with the new display and accept delivery of the computer after the contest. However the discount was very attractive.

Instead I relied on my ancient laptop running Vista. The Wi-Fi is dead as are all but two USB ports. Since it decided to stop talking to my USB hub a few weeks ago I had to disconnect the mouse and had to deal with my palms riding the track pad while typing. That caused occasional odd behaviour in the logging software. The working USB ports were needed for the FTdx5000 and WinKeyer.

This PC is a liability since it doesn't have the RAM or processor capacity to open more than a few N1MM Logger windows, or windows that update frequently. For example, I cannot open the band map to see my self spots. Instead I relied on the rig's memories and VFOs to mark stations I wanted to work later.

Oddly enough the laptop chose the very next day to finally try to catch up with dozens of Microsoft updates that it seemed unable to process for several months. Perhaps it knew that it was about to be put out to pasture.

Inverted vee for 40 and 80 meters

Since I am behind in my project to build an 80 meter vertical array, and there is no feed line yet to the XM240 I decided to throw together a two-band inverted vee for 40 and 80 meters. It is a temporary antenna designed to get me through the winter season.

The core of the antenna is the 80 meter inverted vee I put up on the Trylon last winter. To this I added a 40 meter inverted vee I had on my tower back in Ottawa. That is, it's a fan wire antenna using PVC pipe sections to hold the wires ~18 cm (7") apart. The apex is ~32 meters on the big tower, a few meters below the Explorer 14. The ends are held down by rocks in the hay field, far enough out for the interior angle of the vee to be ~100°. If you look carefully you will see the tower mount in the picture above. The wire and spreaders are especially difficult to pick out.

There was no time to tune the antenna since it went up only hours before the start of the contest. We could do no more than put it in place, untangle the wires and connect a spare run of LMR400 to a 60 meter run of FSJ4 flexible ½" Heliax going back to the switch box.

As expected it tuned well on 80 meters but not on 40. Due to capacitive end effects between the higher band element and the longer one the 40 meter inverted vee is electrically longer and resonates below 7 MHz. In the minutes before the start of the contest I trained the rig's tuner throughout the 7.0 to 7.1 MHz band segment and did a quick comparison with the multi-band inverted vee on the Trylon.

For most DX the higher inverted vee was 1 to 2 S-units better. On US stations the lower one was equal or better on stations in the US northeast (very short path). The higher one was better on the majority of US stations. On 80 meters I had nothing to compare with other than the Beverage on receive, from which little or nothing can be concluded. I fared poorly on both 40 and 80 meters in the contest, apparently more due to propagation than my antennas since others suffered similarly.

The antenna works though obviously not so well as what I had planned for 80 meters and not what I should expect on 40 meters once the feed line is connected to the XM240. I estimate that I'll get another 2 S-units for the yagi from a combination of height and gain. The inverted vee is needed for the winter to provide an omni-directional option on 40 meters to switch to when needed. It will be interesting to compare when the 80 meter vertical comes online this winter.

Side mounted yagi to Europe

Most hams who put up a tri-bander have one similar in size to the Hy-Gain Explorer 14. The boom is short at only 14' (4.2 m), having 3 active elements on 20, 15 and 10 meters. If it's all you have it is possible to be perfectly happy with it and work the world; it performed well enough to help win two CQWW plaques for QRP contesting from Ottawa. When you have another antenna for comparison the compromises inherent in a short boom yagi become apparent.

The antenna is fixed at ~35 meters height and a heading of 45°, towards Europe. It is much higher than the only other high band antenna I had for the contest, a TH7 up 21 meters. Height helps though not as much as desired. Before the contest I rotated the upper yagis towards north to, in part, minimize any detrimental interactions between the still unusable TH6 and the Explorer 14. That both antennas use identical traps assists with a direct comparison since element loss is similar.

On 20 meters, there was little difference between the Explorer 14 and TH7 towards Europe. Although disappointing this should not come as a surprise. Yagi gain is primarily a function of boom length, not number of elements; both antennas have 3 active elements on 20 meters.

The picture changes on 15 meters. Despite the longer boom and an additional director on the TH7 the higher antenna is clearly superior by at least 1 S-unit. That was welcome since at this point in the solar cycle the European openings on 15 meters are not as strong or deep as other times. Regrettably there was no opening on 10 meter so that comparison was impossible.

F/B is poor enough on 20 and 15 meters that I could work many US and Caribbean stations while focussed on Europe. The price is increased QRM while running Europeans. On balance I can't decide whether this is a curse or a benefit.

This is a temporary antenna to get me through the winter contest season. Because my tower project lasted longer than expected I had to rely on the antennas that were close at hand. In the spring it comes down to be replaced by...something. I'll be exploring options over the winter based on my experience with a selection of yagis at different heights.

160 meters

My results on 160 meters were similar to 40 and 80 meters primarily due to poor conditions. I continued to do well in the pile-ups on DX towards the south and worked as far west as Hawaii. This was with a 3 db handicap since I had to dial back the FTdx5000 to 100 watts from 200 watts to qualify for the low power category.

What frustrated me was little success towards Europe during the contest, managing to work only a handful. Did the antenna have a serious failing despite modelling that showed only a modest impairment in that direction? I was relieved to discover after the contest that I was not alone, with everyone on this side of the Atlantic Ocean having the same experience.

The answer may be that QRM and noise levels happened to be worse than usual in Europe. After the contest those woes continued. I did manage to work 9G5W despite copying difficulty on their side of the QSO. It may be that my only permanent solution for top band success will be an amplifier.

Antenna switching

When I picked up a secondhand 2x8 antenna switch a few months ago I accelerated my plan for SO2R and remote switching. Although I fell far short of SO2R for this contest I did complete the basics for switching antennas.

All transmission lines terminate at a tower base where there is a housing for the switch. Control lines run back to the shack along with two runs of LMR400. This is mostly a temporary setup since the coax is not rated for burial.

Switching is entirely manual rather than rig or software controlled. I quickly built a control box with only one side active. The numerous "blanks" are there for future control of an 80 meter array direction and Beverage selection. Or I may go entirely software control.

I'll have more to say on antenna control and automation in future, which is a complex and important topic. For this contest I kept it simple, and it worked fine.

Empty calories

As the contest progressed and I knew that I'd fall short in my quest for multipliers I altered my strategy so that I could still turn in a competitive score. I didn't yet know that others were suffering similar propagation woes, and that the fault wasn't not entirely due to me or my half-built station.

With multipliers difficult to come by I spent many hours ignoring the chase entirely to instead park on a frequency and call CQ. My intent was to work as many US stations as possible, on every band that was open. These QSOs earn fewer points and are free of any multiplier value. For the Americans it's a win since they get an easy QSO in the log.

Since I look upon CQ WW as a primarily DX contest these QSOs feel a bit like the empty calories in our diets that frustrate nutritionists. They're filling but not optimal to our health. I appreciate every one of these QSOs yet feel that I'm missing out while I'm filling up the log. Yet it's a necessary step to a high score. Unfortunately for the US contesters it's an asymmetrical dynamic since they far outnumber Canadians. This is a contest in which scores between US and Canadian entrants are not comparable.

In between or even during runs I would check other bands for multipliers. This is how I worked a few unexpected multipliers on 10 meters, which was barely open, and then only occasionally.

Here, have a peanut

I'm the sort of person who is always snacking. Especially when the rate slows I am sorely tempted to run to the kitchen and grab something to eat. Since I've been gifted with a particular metabolism there is no threat of weight gain! However the temptation can impact results if it takes me away from the rig.

My solution is to keep a container of trail mix at hand. I use it as a reward system. If a run is going particularly well I'll grab a few seeds while the computer is sending a message. I'll eat a tastier nut when I score a multiplier.

It may seem silly but it works to keep me focussed and in the chair.


After a big contest I enter a several days long lull during which I tend to avoid getting on the air or doing anything radio related. Very soon I'll return to working on the station. It's a big, challenging project and it's clear that even with carefully thought out priorities I won't achieve all I planned in 2017.

Winter is an opportunity to relax, do a lot of operating and contesting and less challenging antenna work and improvements in the shack. I'll be busy without the same frenetic pace. At year end I'll do my usual annual review and look forward to the coming year. There's lots of hard work ahead, along with joy of learning and achieving my goals. 

Sunday, November 19, 2017

160 Meter Antenna, at Long Last

One of the great advantages of a big tower is that it is downright trivial to put up simple wire antennas that perform well. I have now built the 160 meter T-top vertical I modelled earlier, tuned it and put it on the air. It works great for a temporary antenna. Next year I'll roll up the radials and store the antenna during haying season.

Choosing a permanent high-performance 160 meter antenna is not a priority for this year or next. I hope to get to it eventually.

The picture of the upper part of the antenna is annotated since it is otherwise difficult to see the 14 AWG wires. With radials attached it resonates at 1.750 MHz. This is 80 kHz lower than in the model, or 4.5%. That's a lot! Using percentage is helpful since a few kHz of error is deceptively small at low frequencies. Perhaps there is more coupling to the tower or guy segments that the model dealt with, or perhaps the ground differs markedly that what is in the model or that NEC2 can accurately calculate.

For a single element antenna of this type the error is not critical -- there is no F/B or main lobe to optimize -- so I trimmed the 22 meter vertical wire down to the designed 21.5 meters and compensated the rest with an L-network. The L-network is required in any case due to the low radiation resistance. Low radiation resistance is a feature not a bug, as we'll see.

Design departures

I did not follow my original design exactly. The biggest change was to reduce the radial count from 16 to 8. For a temporary antenna I did not want to take more trouble than absolutely necessary to get an acceptable signal. The radials are as designed: 30 meters long. It only makes sense to go with longer radials -- λ/4 or more -- for a far greater number of radials.

Since the AWG 18 wire spools I ordered contain 150 meters of wire there are exactly 5 radials on each spool. I was surprised there was no overage on the spools. When I added short tails for wrapping the ends the fifth radial came up short 50 cm. It seems when you buy 150 meters of copper these days that's exactly what you get.

The catenary is tied off a couple of meters lower than the design to avoid crossing the prop pitch motor mount. This does not effect performance or the length of the vertical wire. All it does is move the ground anchor further out away.

I swung the antenna to be SSW of the tower rather than SW. The model shows that this change increases gain towards Europe (NE) almost 1 db. However it places the antenna wires, especially the T-top wires closer to the guys. As speculated above this may have caused the change in tuning. I did make sure to model the antenna wire as insulated -- which would lower the resonant frequency, as it measures in practice -- so that is not the cause of the difference.

First try

I planted a copper ground rod where the vertical wire hangs for easy radial attachment, wrapping the radial ends around a stainless hose clamp that holds them tight to the ground rod.

After the first 4 radials were laid I measured the impedance. This brought a surprise. The radiation resistance was almost 10 Ω higher than expected. Can you see why?

Suspecting the cause I returned to the computer to play with my EZNEC model. I added a direct connection to the MININEC ground through a resistance load representing a rough guess at the impedance of the ground connection through the ground rod. Sure enough the radiation resistance rose from 24 Ω to almost 33 Ω.

The purpose of the radials is to provide a low loss return path for the near field of the antenna and to keep those fields from circulating through the lossy ground. The ground rod routes a portion of the current directly via the ground. It's self defeating.

For my final design I replaced the ground rod with a short length of ABS pipe. The radials are attached in the same way. The difference is that the radials are now isolated from ground.

Measuring again, the radiation resistance dropped to 27 Ω at resonance. This is a significant improvement. Keep in mind we are trying to improve antenna efficiency, not add so much loss that there is a direct match to 50 Ω transmission lone. As I said above, a low radiation resistance is a good thing to see. The match comes later, in this case one day later.

L network

Once I had all the radials attached and the antenna tuned as much as possible without shortening the T-top I measured the impedance at 1.830 MHz, the centre of my CW contest and DX band segment, I sat down at the computer and designed the L-network. With modern software this is trivially easy. I used TLW to do this, as I have had good success with it for other antennas.

The 31 Ω resistance is several ohms higher than at the 1.750 MHz resonant frequency. Radiation resistance tends upward above resonance. Neither is the reactance a surprise since the antenna is long at 1.830 MHz. As you can see the feed point SWR is quite high primarily due to that inductive reactance.

I chose a "low pass" style of L-network since it offers modest attenuation of harmonics which could cause problems in a multi-op or SO2R contest setup; this is handy right now since I don't yet have band pass or notch filters. Experience tells me this is tolerable for 100 watts. Another benefit is that the coil size with this style of network is usually small.

I reused the L-network from the 80 meter tower vertical I had at my Ottawa QTH. I wound a new coil from insulated AWG 14 solid copper (bought in bulk) on a scrap piece of 1" PVC pipe (~1.3" OD). The wire's insulation makes the coil diameter slightly larger than the form.

For a capacitor I used a high voltage 2,200 pf disk ceramic. All the door knob capacitors I have are no more than 500 pf and if I add them in parallel there is no room for them in the small enclosure. The ESR of the chosen capacitor is probably not very low but based on the network design the power dissipation should be low when running my rig at maximum power of 200 watts. Next year I'll revisit this, or sooner if the capacitor fails.

Notice the SWR curve above. A computer, an hour in the workshop and a trip out to the field and the SWR is perfect. No further adjustment needed for an SWR of 1.0 at 1.840 MHz and a 2.0 SWR bandwidth of 100 kHz. I displayed my confidence up front by using fixed C and L components.

On the air

I had planned to leave it be for a couple of days to haul Heliax across the field and up the tower to get the other antennas connected. Then the weather closed in with freezing drizzle making the towers unapproachable. Instead I grabbed my newly connectorized rolls of LMR400 and a couple of UHF barrel connectors and made a 260' (80 m) run directly to the shack. Cable splices were propped up on spent wooden cable reels and tightly wrapped with plastic bags for temporary weatherproofing.

In the shack the SWR remained excellent. The bandwidth improved slightly, probably due to loss in the ancient bit of RG213 I grabbed to span the last 10 meters to the feed point. Then I waited for the sun to set.

There were a couple of European contests going on and I could hear them well on the northeast Beverage. On receive the vertical is of course far noisier. Even so many of the Europeans could still be heard well on the vertical, and not very well on the 40 meter inverted vee. My initial hypothesis is that the vertical is achieving lower radiation angles that allow it to hear DX better than the noise increase would suggest.

In other directions the impact was stark. My first QSO was TO2SP in the Caribbean, who was loud on the vertical. On the northeast Beverage his signal was almost unreadable. I had a similar result with US stations who were well over S9 on the vertical and extremely attenuated on the Beverage. The second night I worked J5T and pushed through a couple of small pile ups. That bodes well.

On a few DX stations far to the south they copied my 200 watts better than I copied them. That could pose a problem. Towards Europe and the Middle East I could copy signals quite well on the Beverage while they heard me not at all. It's a combination of not having an amplifier and, perhaps, poor receiving conditions on the other end.

Need...more...Beverages. But that's a winter project, not for now when more important antenna projects beckon. For the present I am very appreciative for what I have on 160 meters.

Obstacle course

I may have to move the radials this week for the remaining work on the tower. Since the antenna is only 20 meters from the big tower and the radials are 30 meters long there are many opportunities for accidents. I know where the wires are yet I have a habit of stepping on them. Others don't have even that foreknowledge.

In any case the LMR400 runs are needed for the two runs from the shack to the 8x2 switch I've installed away from the house (more on this in a future article). I can live without the 160 meter antenna for a couple of days. It's only real purpose for the next few days is to become familiar with how it performs and identify its capabilities on the air and any grievous deficiencies.

Once I've installed the intended 200' (60 m) coax to the switch box I'll weatherproof everything and leave it be for the winter. The next few weeks will tell me whether this antenna can deliver the results I want. First up is the CQ WW CW contest and then the ARRL 160 meter contest. I have high hopes for this, my first real antenna ever for top band. There are many things you can do on 50 acres that you cannot do on a suburban lot.