Modelling Ice on Yagis

On the second day of the recent CQ WPX SSB contest we had an ice storm (freezing rain). All my antennas survived the moderate amount (up to 5 mm) of ice. The impact of the storm was far worse to the west of us, with many lost trees and antennas. The high SWR of most of my antennas made operating the contest a hassle. I don't really like WPX so it was no great loss.

This is not the first time I've dealt with ice; it's a common weather event in this region. I know from experience how ice has mechanical and electrical effects on wires and aluminum elements, and towers. The major worry is antennas and towers breaking and even falling to the ground. That is a serious hazard. The electrical effects are not often given the same attention. These may only come to the fore during important operating events like contests.

The electrical effects are unsurprising. Ice is a dielectric so it behaves as a lossy insulator. That lowers the VF (velocity factor) and therefore increases the electrical length. The same is true for antenna made from insulated wire. But the effect of wire insulation is fixed and therefore constant, and that can be quantitatively dealt with during design and construction.

The variable effects  of ice depend on the amount of ice, whether it coats all or part of the element circumference, the presence of impurities (dirt), and of course its weight changes the shape of the antenna (droop and sag). Ice, like most insulators, has loss so there is a reduction of gain, ranging from small to large.

It can easily be enough to shift an antenna far outside of the band(s) for which it is designed. Some antennas are affected more than others, depending on their shape, orientation and Q. Here is a rundown for my antennas during the recent storm:

• Beverages: They worked despite sag and icicles on the wires. Performance may have been worse but there is no easy way to determine that. Beverages can be forgiving antennas when subjected to non-destructive assaults.
• 80 meter vertical yagi: Resonance shifted down only a little so it remained usable. I suspect most of the impact was on the parasitic wire elements.
• 80 meter inverted vee: Wire sag and resonance shift were substantial but they went in opposite directions: higher and lower, respectively. The SWR was a little higher but the antenna was otherwise okay.
• 40 meter yagis: The effect was greater on the big 3-element yagi and less on the 2-element XM240. Perhaps that was due to antenna Q, although the inductively loaded elements of the smaller yagi has a similar effect.
• TH6: Moderate resonance shift. It remained usable on all 3 bands but the SWR wa a problem high in the phone segments. 
• Skyhawk: Similar effect as for the TH6 but less severe. It remained usable.
• 5-element yagis for 10, 15 and 20: The effect seemed quite acute on the 15 meter yagis and moderate to large on the other bands.

Freezing rain requires unusual atmospheric conditions so that it is uncommon even in regions with cold winters. Where I grew up in VE4 (Manitoba) they were rare; it was too cold for ice storms. In eastern Ontario they happen more often, perhaps 2 to 3 times per year, mostly in late fall and early winter, but they can occur mid-winter. It is important in this climate to design towers and antennas to survive ice loads of up to ½" (over 12 mm). Of course many do not, out of unconcern or relying on luck.

The ice coating can surround antenna elements or just sit on top. The liquid water of the cold rain has only a brief period to flow to the bottom of the element before it freezes. Wires are narrow so they tend to have a coating of roughly constant depth (left). It takes more freezing rain to fully surround yagi elements. The coating typically has a corrugated appearance and can have icicles.

The mechanical effect on wire and aluminum tube antennas is different. The weight of the ice can far exceed that of the wire and cause extreme sag, such as the inverted vee on the left. The ice lowers the resonant frequency while raising it due to the more acute interior angle. However, they are unlikely to exactly compensate.

For the same amount of ice on yagi elements the effect is less severe. Rather than sag in the centre, the elements ends droop. Moderate droop does affects antenna elements a small amount since the centre, where current is maximum, remains straight. But, as we've seen, the resonant frequency will be lower.

Even if an antenna survives an ice storm, that isn't good enough; a mechanically sound antenna can become useless when covered in ice. That can prove very inconvenient if it happens when you really need it: contests, DXpeditions, etc. As you can see in the above list, some of my antennas fared worse than others. This is especially true of the 5-element yagis.

How bad is it? It is easy to add ice to antennas in modelling software so that's what I did. The wire group editting feature in EZNEC was very helpful in this exercise. 

Fresh water ice can be modelled as an insulator. All we need to know is the dielectric constant, thickness, and loss tangent. Rainwater contains impurities that are difficult to predict so I didn't bother. This study was intended to roughly quantify the effects of ice, not to make precise predictions.

For fresh water ice, the several references I reviewed closely agree with an approximate dielectric constant of 3.15 and a loss tangent at HF of about 0.1. I first tested the model of the 5-element 15 meter yagi with ⅛" (~3 mm) of ice, with the antenna in free space. Using free space simplifies the model to focus on the variables of primary interest, rather than far field pattern and ground interaction.

The 15 meter yagi has a distinct SWR curve. The first dip (SWR of 1) at 21.1 MHz serves as a key marker. The second minimum help to further validate the integrity of the model when ice is included. The base azimuth pattern is taken at 21.2 MHz. The second pattern, with ice included, is at 20.7 MHz, in proportion to the calculated SWR shift. Notice that the patterns are identical other than loss for the ice-covered yagi.

It is assumed that the ice is constant depth for the full circumference of all tube diameters used in the elements, in this case ranging from 1" to ½". The model uses a hairpin (beta) match, since it is far easier to model than the gamma match on the real antenna. Other than the different effects of ice on the matching network (not included in the model) the SWR curves are almost identical for both matching networks.

With this modest amount of ice the antenna resonance is shifted downward by 500 kHz. That's surprisingly large for such a small amount of ice. Yet my experience agrees with the model. Ice causes the SWR to be very high across the 15 meter band, and especially on phone for the WPX contest. The noise floor when switching to the 5-element yagis (either or both in the stack) is eerily quiet.

If the scaling effect of the ice is to be trusted the full SWR curve should remain intact, as should the antenna pattern. The SWR curve scales well with only a small deviation of perhaps 25 kHz between the two minima. The patterns at 21.2 and 20.7 MHz are identical other than less gain for the latter (the plots show only the azimuth patterns). There is loss in the ice since it is not a perfect insulator.

With these favourable results in hand I collected model data for my 20, 15 and 10 meter 5-element yagis with radial ice depth from ⅛" to ½" (3.2 to 12.7 mm).

As you can see, the effects are quite large and they increase with frequency. The effect gradually tapers as the ice depth increases. Gain/loss was calibrated to 14.15, 21.2 and 28.5 MHz for each 5-element yagi, and validated by the aforementioned pattern and SWR markers.

By the point where you have ½" of ice on your antennas you probably have more important concerns than yagi performance! The SWR and gain of a broken antenna is not the concern.

Above is the roughly calibrated (450 kHz width of the the band) SWR curve of the 15 meter yagi with ½" of ice. The models became increasingly difficult to calibrate when the ice is thick. The familiar SWR markers (as noted earlier) have become vague for all 3 yagis. The expected patterns remained the same despite the changing shape of the SWR curves, so that served as a further check on the calibration. However, some uncertainty remained in these extreme cases.

This is not precision work! Even so, my method proved to be adequate since my purpose was to gain insights into the effects of ice. I only ever measured the SWR once during an ice storm and my recollection of it for the 15 meter yagi closely resembles my model.

At this point of the study, I had a question: is this a uniquely 5-element yagi problem? That is, are smaller yagis and single element antennas less severely affected by ice than large multi-element yagis? That's more modelling work than I'm willing to do! What I could do was a few models of smaller antennas, and then compare the severity of the effects.

I went through the same exercise with an ordinary 80 meter inverted vee. Its apex is at 20 meters height, has an interior angle of 90° and is resonant at 3.525 MHz (for CW). I did not attempt to compensate for sag due to ice even though it could be significant. That would lessen the change in resonant frequency and increase loss, both due to the smaller interior angle.

The effect was greater than I expected. My 80 meter inverted vee with an apex at over 30 meter did not seem to fare so badly in the ice storm -- the SWR was higher although it worked reasonably well. Yet the model shows that its performance is as bad as for the 5-element 10 meter yagi. 

I suspected that the large modelled effect was due to the larger ratio of radial ice to conductor diameter for a wire antenna. To test my hypothesis I reran the model for #10 and #18 wire, both two steps from the original #14 gauge wire. Other than a small shift in the resonant frequency, the percentage of ice induced shift barely changed. I didn't bother to substitute even thinner or thicker wire to see if that resulted in a non-negligible difference.

The loss for the ice covered 80 meter inverted vee is not as bad as for the yagis. I didn't bother with a plot since the numbers are small. With ½" of ice the loss is -1.0 db. That much better than the 5-element yagis.

I tried a few other antennas in my large model library. Since the modelled effects of ice on these antennas were unsurprising or ambiguous, I decided to stop there. I was satisfied with the insight gained, and that was my objective.

I wish I had a model of the Skyhawk tri-band yagi on hand since its SWR suffered less during the recent ice storm. However, that was only the SWR and it is certain that loss due to ice would mirror that of other yagis built with tubes. It may just be that the Skyhawk is lower Q than many other yagis. The yagis I've designed and built are higher Q than is typical since I tune them for better gain at the expense of SWR bandwidth and F/B. The SWR of my 5-element yagis for 20, 15 and 10 meters rise sharply at the high end of their respective bands.

I have noticed frequency shifts on the 5-elements yagis during heavy rainstorms, though they were of less severity. Heavy snow fall close to the freezing point when the snow is wet and sticks to the antennas has effects similar to that of ice. I was a little surprised by that when it happened the first time. However, snow is not as heavy as ice so there was no structural risk, just operating inconvenience.

I briefly considered the possibility of using these results of this study as a basis to perform reverse calculations. It should be possible to determine the average radial ice depth by the change in antenna behaviour. I don't know whether that would be useful or just a curiosity. The "average" is far from a precise characterization of the variable deposition of ice on surfaces. But it could be done.

This picture was sent to me by a contester (whose call you'd recognize) taken during a severe ice storm several years ago -- he lives hundreds of kilometers from me and there was no ice storm here. All of his antennas survived but it was touch and go. This is the bottom of the support rope for one leg of an 160 meter inverted vee going up to one of his big towers. It's astonishing that the antenna bounced back when the ice melted. Take this as a lesson to build antennas that can survive ice loads if you live in an area where they are periodic events.

The snow is gone and the weather is warming. Soon it will be recognizably spring and worries about ice storms will fade. That is, until next winter! You never know what nature will throw your way. Be prepared for whatever weather risks affect you, be it ice, flood, wind or earthquake.

Making Mistakes Along the Way

Amateur radio is practical: we use what we buy or build. A device can be ugly, deficient, cheap, less than state-of-the-art and still be immensely useful. If it helps you to put a signal on the air you will be successful. There are no asterisks on an operating award because your home brew QRP transmitter was a oddball collection of parts spread across the operating desk, held together with bits of tape and clip leads.

I use computer design tools and breadboards to test my designs. They often remain prototypes for a very long time. Witness my long running project to design and build a digital controller for my prop pitch motor rotators. The breadboard direction indicators sitting on the old 24 VDC power supply and a standalone panel meter is still there and working! Ugly and embarrassing but it gets the job done. 

The new one is getting better although not yet completed. With the weather warming it will take a while longer as my focus turns to antenna and tower jobs. That's okay. I don't need a pretty station to be competitive in contests and the DX pile ups.

Despite all the design and prototyping I continue to make many mistakes. Maybe I discover that a design is deficient and I have to research and try alternatives. Or the design is fundamentally sound but impractical when implementation is attempted. Worse, the design and implementation work, it goes up high on a tower and then fails because it isn't immune to abuse by the weather or the flow of high power. 

I have not been shy about highlighting my mistakes on the blog. And there have been many! I believe my biggest mistake was to attempt to make a hardware-based antenna switching system. At the time I believed that this would be a relatively straight-forward first step toward a software solution. I was very very wrong! It was mechanically and electrically complex, inflexible, overly large and difficult to use.

I recognized my mistake and (reluctantly) discarded it. However, my first software solution was also deficient. I am still using it but it is due for a redesign. The UI (user interface) is confusing to guest operators and even to me at times. I know because I keep pressing the wrong buttons for the wrong radio or antenna. The next version will be much better, I hope. 

There is no shame in making mistakes. That's how we learn. What is shameful is hiding mistakes or denying them and continuing on as if all is well. No one will be fooled by your evasion. Laugh at yourself, accept the lesson and try again -- to err is human.

Other examples of mistakes I've made, and the lessons learned, can be found in the blog. A few examples are gamma matches, 160 meters on the 80 meter vertical yagi, blazing the wrong trail for a Beverage antenna, breakage of scrounged aluminum, and even the choice of manually-tuned tube amps in a station intended to be used by guest operators. Searching my blog for the word "mistake" tags a lot of articles! Many of them are for operating mistakes or small things like forgetting to tighten bolts, but in this article I'll focus on design and construction.

I will also overlook ugly construction. When the ugliness is 100' up the tower, no one will notice but me. When it's on or under the operating desk, I can always cover it. No one dares ask what's underneath the cloth -- most hams have one or more ugly contraptions in their stations.

Analysis paralysis

You've certainly heard this phrase. It means to delay or avoid doing something because there are uncertainties or alternatives. Deciding what is best, let alone perfect, can be fruitless since there may not be one. This is especially fraught when the requirements are skimpy or vague, as they often are for projects hams are wont to build. That is, we really aren't certain what we are trying to achieve. That may be okay in some cases since exploration can be a good way to learn.

The key is to think through the options and research alternatives as well as you are able, then do something. You may choose a poor or non-optimum path, but so what? We aren't building rockets or nuclear reactors where failure isn't an option. When an unforeseen difficulty arises, correct your course or throw it away and try a different approach. Don't stubbornly persist with your first choice, or abandon the project because you are consumed by doubts. 

That said, I strongly advise against jumping into construction with no analysis at all. Many hams work that way, and I did as well when I was much younger. Impatience can be a curse, leading you into the wilderness without a compass. You may find yourself taking two steps backward for every step forward. 

Do at least some planning and design work before jumping into construction, which is usually the fun part. Know your destination and keep aiming at it no matter the bends in the road along the way.

Devil in the details: "minute details can have a big, often negative, impact"

Often the reason we get caught in analysis paralysis is that there can be so many options and details in a project. This is as true for an electronic project utilizing software or PCBs with dozens of components, as it is for towers and antennas where questions about static and dynamic loads, tensile strength and other challenging questions are critical for durability and safety. 

Don't be afraid to ask for help. But for many in-the-shack projects you can work it out without serious risk other than a little money and your time. However, don't simply proceed by trial and error since there are fantastic and free design tools for you to use, and online fora where you can ask questions. Those can help you to avoid many elementary mistakes. Examples of design tools include EZNEC, LTspice, KiCad, Elsie and so many more.

That said, a custom design can entail many pesky details that you will have to work through. The shape or position of one part can impact the success of the project. Let me illuminate this with a project that I am currently working on: a 40 meter reversible Moxon antenna. Let's look at the element switching system component where a relay changes each element to be either the driven element or a director. Both elements have the same component but with the roles reversed.

The linked article contains the switching system design which you may want to review before continuing. The only item from that article I'm reproducing here is the element switching schematic. The central coax switch for selecting the driven element is not included in this discussion. That's for the wire version, while the NEC5 design for the rotatable version I'm building can be found here. Full antenna detail will be published after the antenna is up and working.

On the right is the centre feed point of one of the elements, as it has been assembled in the hay field. On the left are most of the parts for the switching system that will be placed at the feed point. There are a DPDT relay, non-conductive spacers (to support the reflector coil and element connector tangs), solder lugs, custom made aluminum tangs to connect the switching system to the element halves, an ABS enclosure and a coax connector. Here are some of the details I've been considering in the design:

• Minimum enclosure size to accommodate the parts that permits good RF design and that minimizes wind load. It must be strong enough to withstand the weather.
• Minimize lead lengths to the connector, coil and element for low stray inductance.
• Fits over the element hardware and can be secured, while allowing ease of attachment and maintenance. Those tangs will be formed to fit under the hose clamps.

Consider a few of the many details that I must address:

• A high-Q coil tends to have equal diameter and length with space between the turns. For the required 1.2 μH coil those dimensions are on the order of 3 to 4 cm. The fit is tight so I've made the length a little longer than the diameter.
• To adjust the coil (mainly due to lead inductance), one tail must be solid (for support) and one flexible. That is, to compress or expand the coil.
• If the support spacers are too close the aluminum tangs must be positioned outboard of the screws, and inboard if the supports are wide apart. I need them close so that they can be bent outward to fit under the hose clamps (projecting outward from element centre). That increases the risk they could touch, but will reduce stray inductance. Also, the tangs must be appropriately sized (width and length) so that the entire enclosure can be rotated in and out of the hose clamps for insertion and removal.
• Will the enclosure stand on the tangs or be tight against the hose clamps or the large element u-bolts? For the former, the risk is that wind load will fatigue cycle the aluminum tangs and ABS enclosure. For the latter, the risk is that weather and the pressure of the clamps on the enclosure bottom could deform the plastic which might eventually crack.
• Stiff wire must be used for internal wiring so that the relay is held in place by the wires. This is the dead bug style I used in similar cases such as auxiliary coax switches and stack switches. Since #18 solid copper wire has worked in the past I'll use it in this project.

There are other details which I've omitted; there are a lot of them! Perfection is impossible but analysis is still prudent. Yet I will confidently predict that there will be one or more mistakes made in my design and construction choices. 

One mistake already discovered is that the plastic spacers (threaded for #6 screws) won't hold the screws very well when adjusting and torquing the top and bottom screws. Therefore I will place nuts on the bottom screws (for the tangs and solder lugs) to hold them securely. The coil solder lugs on top don't have to grip the spacer as solidly. The screws will have to be cut to measured lengths so that they grip well but don't get close enough to arc or short inside the spacer. 

At this point readers may wonder why I'm going into this excruciating amount of detail. But that's just it: the devil is in the details. Even a simple project entails a large number of decisions about details that will have consequences. Those choices are inter-dependent since they affect each other.

All of us must make many choices, consciously or not, when designing and building any project. When a problem is inevitably encountered, we revise and improve. Mistakes are just part of the process.

There is no escaping the details. Buying a product instead of home brewing also entails details in its installation and use: there are interconnection and system details to be worked out. A station like mine is very complex and it can be a struggle to make everything work in harmony.

Accept that mistakes will happen

Saying that mistakes happen is unsurprising and uninformative. What I tried to communicate in this article is to accept their inevitable appearance no matter how cleverly we design and build the contraptions we use in our stations. 

But it is important that we learn from our mistakes; that's one of the wonders about our technical hobby -- that there is so much to learn. Learning can be fun and fulfilling even though we may cringe when a mistake is discovered dangling from a tower or by the acrid smell of burnt electronics.

We should do our due diligence, while being careful not to obsess over preventing every possible point of failure. There lies paralysis, and that's never good. Move forward by trying something when you're stuck, or get a second opinion from someone with greater experience. 

The only time to stop is if a mistake would risk life or property. That's one time that you are advised to seek an expert. Asking for help is not a sign of weakness. Nor is admitting and correcting a mistake.

Solid State Amp in the Station

Choosing amps can be a dilemma. Tube amps tend to be clean (low distortion) but almost all require manual tuning and the tubes, although they can last many years in a newer product with protection circuits, are expensive to replace, if they can be found. Solid state amps are typically no tune and instant on, but tend to poor signal quality (IMD), and if the transistors fail they must usually be replaced by different ones since they are evolving (and improving) quickly.

I prefer tube amps for their reliability and clean output. That why I purchased an Acom 1500 a few years ago, and for its coverage of 6 meters and excellent protection circuits. The latter is critical for tetrodes just as it is for solid state amps.

Buying tube amps is becoming increasingly difficult to justify. Partly for the aforementioned reasons and also because of guest operators for contests. Many hams, even those licensed for decades, have difficulty tuning amps quickly and accurately in the midst of a contest. It's one of many things guest ops need to learn and deal with in an unfamiliar station. 

I have seen my amps poorly tuned or offline due to an unnoticed fault. The amp protection circuits prevent damage but contest effectiveness is impaired. There are tube amps with ATU (Acom 2000) or with preset tuning points (Alpha 9500) that make them almost (but not quite) no-tune, but they are very expensive.

When an opportunity recently arose to pick up a nearly new solid state amp with a good reputation, I bought it. It's an Acom 1200S. In the picture it is sitting atop the Drake L7 while I tested it. It is paired with the Icom 7600 (lower left) that I purchased last year.

Although the amp receives mostly positive reviews, nothing is perfect. Tubes fail and so do LDMOS and other solid state devices. Perhaps a better tell is that there are not many available on the used market. Skimpy used market data made it difficult to set a fair market value for the amp, which was necessary since I purchased it from the estate of a friend. Two of us have been testing and selling his equipment on behalf of the family.

I now have 3 kilowatt class amplifiers, and two of them include 6 meters. One of the three will become a spare. The Acom 1500 paired with the Icom 7610 will likely remain my daily amp. The 1200S will be amp for the second station, used primarily in contests (SO2R and multi-op). I might split the station for daily use, with one dedicated to HF and the other for 6 meters. I monitor 6 meters quite a lot in order to catch elusive openings.

Let me say a few words about the 1200S before returning to the topic of tube vs solid state amps in my station. I'll discuss the amp's pros and cons from the perspective of my interests. Those may differ from yours.

Pros: 

• Automatic band switching by measuring the input. That eliminates the need to split the CAT feed or to come up with a cable to connect the Icom/Yaesu/Elecraft/etc. band data to the amp. But it needs to a dit or similarly brief transmission, not jumping into normal operation. Hopefully guest operators will catch on.
• The protection circuits are fast and appear to be comprehensive. The one commonly encountered is too much drive for the SWR -- the higher the SWR, the lower the allowed drive and thus the forward and reflected power.
• It's light. That makes it easy to move around. I have accidentally pushed the amp backward by pressing the power button too firmly!
• Perhaps most important for contests, it's easy to use. No tuning, a large display and the colours tell you what you're doing wrong (or right).
• It's only a kilowatt. That makes it easy to stay legal per Canadian regulations, especially for CW, although it's a little light on PEP for SSB. Well, maybe that's just me since there are many that would see consider the power limit as a con.
  

Cons:

• The fan is always on and it isn't the quietest. It isn't loud but I expected it to be quieter when idling since there are no filaments. There are higher and noisier fan speeds when the temperature rises during hard use.
• The T/R relay is louder than I expected. It's louder than my Acom 1500 and the Acom 1000, but quieter than the L7 with its bulky 3PDT relay (I still use the original).
• There is only one antenna jack. Although I have my own hardware and software for automatic antenna selection, it would be nice to have a second port for 6 meters since that antenna is routed separately. For comparison, the 1500 has 3 antenna ports.
• The SWR limit can be a problem for many. In my station that is mostly the case for the non-contest HF bands since I have no resonant antennas for 30, 17 and 12 meters. On the contest bands it is rarely an issue since my antennas are optimized for CW, which I mainly operate in contests. On SSB the drive has to be reduced in a few cases, such as on 160 and 40 meters, and for the TH6. The reflected power must be below 100 watts or thereabouts. It is easy to forget to reduce drive when switching to an antenna with a higher SWR during a contest.
• I am a little uncomfortable with the higher IMD common to solid state amps, and LDMOS in particular. I wish more transceiver manufacturers allowed universal feedback loops for distortion reduction. For example, the DPD feature in the Icom 7610 uses a proprietary interface unique to their PW2 amp.
  

Considering the long list of cons, why would I purchase the 1200S? A solid state amp with more head room or an internal ATU like the RF2K-S or the PGXL (but no ATU) may be superior choices, but even those have their quirks and are substantially more expensive. I may take that step eventually, but not this year.

Every amp has its quirks, good points and bad points. I went into this purchase with my eyes wide open; I am not someone who rationalizes a purchase after the fact. There are better amps on the market and there are cheaper amps. At some point I may replace it with another. However, this one is pretty good and it was available. Time will tell whether I made a good decision.

Every modern amp is expensive. There is no getting around that. If you want cheap, go with a vintage tube amp (but check the tubes first!) and put up with its size, high replacement tube costs, lack of protection circuits and so forth. I sold two of those from the same estate at a recent flea market. There are no wrong choices, just wrong expectations. 

I could fill the blog with the endless rationalizations of hams who are eternally wedded to their amplifier choices. One non-buyer at the mentioned flea market looked over my table of amps and went on an on about the Mercury amp he bought. The same rationalization is also common for antennas, rigs, headphones, and other equipment. I have preferences but I can be persuaded by the performance and features of the unfamiliar or unconventional.

All that said, it is the amp for the second station. It may not see a lot of use. That is, unless another amp fails and I substitute it. Unlike the L7 with its glass envelope 3-500 tubes there is no need for periodic heating of the tubes to maintain the integrity of the seals. It may seem wasteful to have an two mostly idle amps but for my contest operating it is vital to have them ready to go. 

The connections to both the L7 and 1200S are identical and simple. There are just 3: key in, transmitter and antenna. Of course there's also the AC power plug; luckily the plugs on both amps are the same and compatible with my outlets. The amps can be swapped in a minute when they're stacked as shown above. 

If I get ambitious I will reconfigure the station so that one station can be used for monitoring 6 meters and the other for HF outside of contests. I have that flexibility with two 6 meter capable amps. I am sometimes reluctant to warm up the 1500 when a 6 meter opening opening is marginal or brief.

It's a shame that the 1200S doesn't have a second antenna port that I can use for 6 meters. I'll have to deal with it in other ways, such as manual coax switches. I have enough manual coax switches lying around since converting to automatic switching!

One thing I won't miss with the new amp is the post-it notes with tuning suggestions for each band and mode. There will be less stress or reluctance for guest ops when chasing mults and making frequent band/antenna changes.

An Idle Super-station

We are experiencing a major thaw this week. The snow is deep, it's been cold, I had a bad cold, and my personal life has been very busy. That limited my ability to operate (and contest) or to progress many projects. But with the nice weather I did my first tower climbs of the season today -- aligning masts that slipped during a February wind storm.

There has been slow progress but nothing worth reporting. I am eager to see the snow recede so that it is possible to do more outside. It is time to shrug off the lethargy of the winter blahs and become re-energized for the coming season. The burden of family duties is finally receding and that will free up more of my time.

It seems strange to some hams I speak with how much time my station sits idle. Some days it isn't powered up at all, not even to monitor FT8. So many towers and big antennas idle and silent. Is that wrong? Is it a waste? Why go to the effort of building a big station and not use it every spare moment that I have? I'm retired, there's time enough to operate.

There are a couple of reasons. First, I am not often interested in chatting on the air. I've never been into rag chewing or even longer QSOs since I'm an introvert. Indeed, that was how I got into contesting when I was a new ham -- lots of contacts and DX without having to chat. The second reason, is that building the station has always been the objective, not so much using it myself. For many hams the communications is the objective and all the other stuff -- putting up antennas, figuring out transceivers -- is a necessary obstacle to overcome. For me the operating puts an exclamation point on my building efforts that confirms that I've built well.

I've been asked by a several hams to remote my station so that they and others can use it when I'm not. That is not so easy with a complicated station like mine. It also doesn't satisfy my own interests. The conversion could be accelerated with commercial equipment -- thus lessening the time burden -- but I prefer to home brew my own control systems. I do it because I can and it is what I enjoy. That means no remote capability in the foreseeable future. Guest operators have to travel to my QTH.

Regardless of how many hours I put in, how am I using the station when I decide to operate?

• Contests, either casual or serious: Those are weekend affairs and there may only be one per month in which I make a notable number of contacts. That includes the majors like CQ WW CW & SSB.
• DX chasing: I am not a serious award chaser. Indeed, I've never applied for DXCC even though I've qualified for many categories and endorsements based on LoTW confirmations alone. I will work hard to log the rare ones, while I'll play games with the rest. For example, using 100 watts or less to see how well my skills and big antennas compete in the pile ups
• Practice: I am a good operator, but to stay good I can't just operate during contests. From time to time I'll turn on the amp, aim the stacks at Europe or Japan and generate a small pile up. Although I do it at less than contest speed, paddle time is paramount to remaining fluent at CW. I find that a continuous period of sending text (not just 599 73) is needed to reduce my error rate when it counts. I don't seem to need the receive practice as much. I've tried MorseRunner and similar tools but I find them too boring for serious practice. I prefer to get my practice on the air.
• Propagation: I enjoy exploring propagation and big antennas help with that. Whether it's searching for elusive openings on 160 and 6 meters, unexpected or rare long path openings, aurora and occasionally meteor scatter, it's all very fascinating. CQing into a seemingly dead band can have surprising results. Often when I not operating I'll leave the station monitoring 50.313 MHz or 1840 kHz (depending on time and season) to spot unusual and unexpected DX. 
• Using what I build: I never build and forget. Whether it's an antenna, BPF, rotator controller or other equipment, an important part of the pleasure comes from making use of what I build. That's true whether I design and build from scratch or assemble a kit. I am not a natural designer so there has to be that payback to incentivize me to put in the time and effort. The incentive is seeing an on air benefit, such as higher contest scores.

Is that a long enough list? It is for me. Every ham has their individual motivations to get on the air.

It is likely that my interests will change. When I am less able to climb towers my focus will need to change. In any case, I don't intend to grow the station too far beyond where it is now. Age brings inevitable changes to our lives. Maybe at the next solar maximum around 2035 I'll be more into chatting since I will have less ability to undertake major projects. It is even possible that I'll remote the station and live an easier life elsewhere!

But for now I build. Although I have been sidelined by many things lately, there has been some progress. Technical articles have been lacking lately since few projects have reached completion. Here's a quick rundown of the projects that I'm actively working on. Expect articles when each crosses the finish line.

• The prop pitch motor (rotator) controller is essentially complete. Unfortunately that does not include the interface to the power supply. There is cabling and testing yet to be done. The software is far enough advanced that I can use it as is and improve it after the new controller is installed.
• I have resumed work on the 40 meter reversible Moxon. I am working on the element trusses and the switching system. It'll be a few more weeks before I'm ready to raise it for testing and tuning.
• I am designing and will soon begin construction of a swing gate side mount. The first will be for either the lower 5-element 15 meter yagi or for a new 17/12 meter yagi which I have designed but not yet built. If the swing gate works well I'll build another.
• My small chainsaw died. It has been replaced so I've resumed tree clearing. The snow got so deep and the weather so cold and windy this winter that I cut down far few trees than planned. I need to get it done before the ticks emerge. I also need to clear trees along the Beverage lines since spring will soon be upon us and I won't be able to access the bush again until fall.

While I keep busy with ham and non-ham projects, my station will remain mostly idle. I'm okay with that.

Politics

The title ought to read: Politics and Amateur Radio. This is not a politics blog. I won't discuss politics, but I am occasionally willing to discuss the intersection with amateur radio. There can be many impacts, and this is one of those times. At least in this country -- hams are citizens and patriots. Present circumstances are worth a brief article.

I once discussed amateur radio and war on this blog. This is not so terrible but hits closer to home. After all, a small number of democratically elected governments are playing badly with each other. Hams are making choices, as they must. I don't know how many hams on the US side of the border (if any) care, nor will I ask. Well, it's just politics and why would hams pay attention to that stuff?

Let me take you through some of the impacts on and reactions from Canadian hams. I don't know everyone so take this information under advisement. Yet I know enough and far more non-hams, and their behaviours are identical.

Travel

We've been here before and yet the vehemence of the reaction is unlike any that I've seen. Ever. Canadians can be incredibly easy going but not now. Almost every ham and non-ham I know that had planned travel to the US has cancelled. That's saying a lot. Not everyone of course, so don't be surprised to see the occasional VE portable W-something.

I'm not going to Hamvention. That isn't saying much since I had no plan to go. It's nice but once every several years is enough for me. Others go every year. Not this year. I wonder how many VE2/3 name tags will be seen this May?

Purchasing

The amateur radio market is small and shrinking. Decades ago there were many ham radio equipment retailers across the country. Now there are only a handful and they are taking extreme measures to survive. There are fewer brands, small inventories and no in-house warranty repair. They have diversified into non-ham electronics, and that may now be the majority of their businesses. Many hams now purchase from retailers in the larger US market. 

Foreign manufacturers have few international distributors and certified repair centres. It is no surprise that many serve Canadian hams from the US. That has just become a big problem since many hams refuse to purchase from the US. Again, not all. I see reactions from absolute refusal to shrugs. I am not planning a major purchase for the next year, but if I do it will pose a dilemma.

The label of "foreign" itself is fraught. When I look at brands like Icom and Elecraft, I see both as foreign. Many hams have treated brands like the latter differently. Not now.

It's not just major purchases. US distributors for parts, certain antenna components and other items are commonly used since it is convenient. Some will change their purchasing habits and some won't. It's difficult to assess how behaviours might change.

Used purchases are unaffected since the transaction is local. Local ham flea markets are safe!

Participation

There are hams that refuse to enter contests sponsored by US organizations, and have qualms about LoTW and other services located in the US. I have not changed my behaviour. I still talk to Russians and hams in other problematic countries. Hams communicate and I won't stop doing that. 

The refusniks are a small minority of hams. But they exist and they can be very loud. I know a few.

Attitudes

Everybody has an opinion, and many are too happy to tell you their opinions. I suppose it's understandable to want to blow off steam and get affirmation from others with the same opinions, and even winning others over to their views.

I am not so easily swayed. I listen to the talk and mostly stay silent. Of course I have my opinions but I feel no need to impose them on others. I carefully navigate the social interaction minefield. Speakly loudly is not helpful since opinions are not actionable.

It is understandable that Canadian attitudes to Americans are influenced by politics, and hams are citizens in this regard. It has always been thus. On the other side? Silence.

On the greater global stage, ugly politics may be a small thing. But small things can and do have impacts that will endure for a very long time indeed.

Desktop 12 VDC (13.8) Distribution

I go through small 13.8 VDC linear power supplies like they're candy. I keep several around since they're vital to my station. They run my antenna switching system, stack switches, antenna switches, Beverage antennas, BPF (band pass filter), rotator controllers, and much more. They are prone to failure due to lightning and other mishaps.

My problem was ease of connection and disconnection, and cable management. Having a multitude of peripherals makes this difficult. I had to manually disconnect multiple wires on the +ve and -ve power supply terminals while preventing shorts and loose wires. 

It is made more difficult since the power supplies are located on the sub-shelf so that I have to squat down behind or underneath the operating desk which inevitably causes unintended damage, such as to my head. 

Wires inevitably go astray when connecting several to one screw terminal. Some of the DC cables end up snaking and tangling amongst other cables, making them difficult to route and connect. I can never remember which peripheral is connected to which power supply, and it can change frequently. Tracing cables is time consuming. 

I have to do this often since my station is constantly evolving. There are partially built projects on the operating desk while I'm building and testing them. In short, it's a maddening mess. I finally decided to do something about it.

My solution is not novel, or even particularly interesting. But it's necessary, and that makes it worth a brief description. If you're looking for excitement, this article isn't it.

Standards

There are many connectors, both standard and proprietary. We are not talking about high current or demanding applications so there is no need to do anything fancy. My solution is that of all my DC powered peripheral equipment: 2.5 x 5.5 mm DC power connectors. There are similar connectors in different sizes but these are what I've chosen.

They are commonly found in smaller devices on our desktops. They're cheap and effective. However, do take care that the ones you order online are not so cheap that they have unwelcome problems. Some require unreasonably large chassis holes, have unexpected threads, might need the male connector to be jammed in full depth and so forth. Paying double the price for good connectors is still cheap.

Interconnection cables are also cheap to buy if you don't want to build your own. For this project you need male connectors on both ends of the cable. The only bare wire connection is to the power supply terminals.

Power supply choice

I recommend against using the DC supply powering your rigs. Although they may have the headroom to deal with a few extra amps there are other considerations.

In my station, many of my peripherals support antenna switching systems deployed in the field, either on the towers or on the ground. These systems are at risk of lightning damage. In a pinch I once connected my peripherals to my 35A Astron linear power supply and lightning fried several components. I eventually fixed it but I have never made that mistake again. They're expensive to replace and can be difficult to diagnose and repair. 

Small linear supplies of 3 to 4 amps are flea market bargains. Buy a couple of them so that you always have a spare. If you are unfortunate enough to experience lightning damage they are cheap to replace and perhaps not worth the trouble of repairing them. Lightning protection is worth considering, such as GDT (gas discharge tubes) which are inexpensive and effective.

Distribution

I don't want to see the DC power supply and cables. They're necessary and nothing more. However they must be accessible for station changes and periodic reconfiguration for multi-op contests. That requires proximity of the connections to each station and to equipment that is never moved. Long cables should be avoided since they can create a mess and are prone to RFI.

I built two connector strips that are wired together. They are constructed from ¾" aluminum angle with holes for the connectors and strain relief. Holes on the other face are for #6 wood screws to affix the strips to the underside of the desk -- ensure that connectors and wires don't block hole access. Most stations only need one strip, but I wanted two so that the cable runs are kept short when I set up for multi-op contests. 

There are numerous other variations that might be preferred. For example, one power supply per strip, or strip interconnection with a DC power cable (occupies one connector on each strip). It is also possible to add RFI and lightning protection on the distribution strips if it isn't present elsewhere.

Installation 

The only important question is where to place the connector strips. I placed mine under the backside of the desktop. However the power bars and a few other items had to be temporarily removed to make space for a screwdriver. One final electrical test and I was done.

I now need to be more serious about attacking the rest of the spaghetti cabling. I always start with good intentions so that every time I first set up a desk it's pretty clean. It gradually deteriorates with every station change or shuffling of equipment.

That was a boring project, wasn't it? Keep in mind that a worthwhile project does not have to be exciting. More like a chore than a project, but still important to do.

I'll return to more interesting topics after I deal with non-radio matters that are currently occupying my time.

2-Man M/2 in ARRL DX CW

The M/2 category is many contests allows two simultaneous signals on two bands, without restriction on who they can each contact. Thus, you can have both stations running, and not restricted to hunting multipliers. There can be additional stations operating S & P on the same or different bands provided they operated within the constraints of maximum band changes per hour (typically between 6 and 10) and never having two simultaneous signals on the same band. 

M/2 is a popular category since it keeps more operators in a multi-op entry active and involved without the burden of competing in the M/M (multi-multi) category. I hosted M/2 teams for the CQ WW CW and SSB contests in 2023 and I operated M/2 at VE3JM at least once. The plan was to do so again for last week's ARRL DX CW contest. There is friendly rivalry with VA2WA about 200 km east of us. Last year we surpassed them, but it was close.

Our plan fell apart a few days before the contest. One team member fell ill. Then we were walloped by two successive snow storms, one a few days before the contest and another forecast for the weekend. About 70 cm fell in the vicinity of Vlad's contest station. One of the operators wouldn't abandon his wife to deal with the second storm. especially since he had no idea when he could return. Our last minute attempt to recruit others was unsuccessful.

It came down to just Vlad and me. I nearly abandoned because I was busy dealing with a family matter. Since that required my presence in a town only 70 km from Vlad's station, before and after the contest weekend, I decided there was no reason not to participate in the contest.

I had a surreal drive down Canada's busiest highway (401) that was still partially snow covered from the first storm. The ditches and median were littered with countless car and truck wrecks. There were even more during the drive home after the contest from the second and worse storm. 

When I got there late afternoon on Friday we discussed the pros and cons of entering M/S or M/2. We read through the rules, considered our expected stamina and the effects of the geomagnetic storm. We chose M/2 because it would be more fun and both of us were accustomed to operating 48 hour contests. We intended to do our best without expecting to be very competitive among other M/2 entries. 

Vlad set us up to participate in the online scoreboard. Then we shared a pizza and got down to business when the clock struck 0000Z.

Note: The rest of this article is primarily of interest to contesters. Others might find it less so. There are no pictures since I was too busy operating. Vlad has updated his QRZ.com page which is full of pictures.

Propagation

A K-index between 3 and 5 for most of the contest did not bode well for the score. Everyone suffered, though not equally. As is typically the case for geomagnetic storms, those of us in the auroral zone feel it more. Indeed, anyone whose signals must pass through the zone feel it. It's just that we see attenuated signal on most paths, including the all important one to Europe.

Those nearby in W1/2/3 and VE1/VO1 tend to fare better since they can "slide" under (south) of the zone. That said, almost everyone was affected. When we're all in the same boat, all scores are lower. Too often we would simply run out of propagation. Openings started later and closed sooner. Signals were weaker and thus many small stations didn't get into our log. Either we couldn't copy them or they simply gave up and turned off the radio. Stations further north (TF, OY, OH, etc.) or in the southern auroral zone (Antarctica) were exceptionally weak.

160 meters is less affected since signals tend to stay below most of the disturbed layers of the ionosphere. Even so it was surprising to see country totals over 50 for many of the big guns. We managed 49, which is pretty good since with just the two of us we couldn't check conditions frequently or make timely band changes. DX openings didn't last long but there were enough of them to make a difference.

When propagation resulted in especially low rates, I might take a brief break to eat, make coffee or check my email. Just 10 minutes is enough to feel refreshed and return to the grind. Towards the end of the contest the conditions improved and we were able to finish strong. 

Station set up

The two run stations were Flex with a PGXL amp, and a K3 with an AL1200. Since there were just two of us we each adopted a station that we used throughout the contest. I am not very familiar with Flex equipment so I took the latter. The third station was for in-band, which could not be used.

We used DXLog which, frankly, is not my favourite. It works quite well but with an unfamiliar interface, the default colours and fonts are atrocious and the function keys never seemed to do what I expected. Other times DXLog would get into a peculiar state (Vlad told me to hit ESC a few times) or a wrong key press would wipe a half completed QSO. Then I'd have to appear an idiot by requesting a repeat of the call sign, unless I was lucky enough to remember it. 

There are other things I could say about DXLog but I'll stop there. It isn't really fair to complain when many problems may be the operator (me) unacquainted with the software. For example, with N1MM I am used to controlling RIT with the up/down arrow keys. Those are used to navigate the log in DXlog. I had to use the radio; if there's a keyboard method I don't know it. The K3 display is quite small so that the RIT value (+0.02 etc.) only display when the knob is turned. I had to manually reset it after every use since I could not reliably remember its value.

Another quirk of the K3 that I don't like is the receive audio quality. Some have raved about its crispness. That is not my experience. When I get several near zero beat callers, it's sounds like someone scratching a chalkboard with their fingernails. Also pretty bad is that the AGC doesn't compress the audio as much as I'd like. If I turn up the gain to copy a weak signal, when the next caller is strong the audio is painfully loud. The K3 was wonderful when it was new but today we have better rigs.

I am comfortable with a manually tuned amplifier, so it was easy to tune it quickly after band changes. We didn't do that often except to chase multipliers on other bands if we had hourly band changes remaining.

Antennas were selected within DXLog and antennas could be turned manually or via digital entry of the bearing in the call sign field of DXLog. It worked well. One day I'd like to do the same for my customer antenna selection software. That won't happen quickly unless I get impatient and use a commercial product. 

The two tri-band yagis have VA6AM triplexers so we could both use them. However, we didn't always agree on the direction! There were enough antennas that we negotiated solution that satisfied us.

As for the antennas, Vlad's station is different but similar in capability to mine. There are stacks on the high bands, either 2× or 3× 4/5-element stacks to Europe and rotatable top yagis, plus a long boom 7-element on 10. On 40 meters there is a rotatable W6NL Moxon at 140' and an XM240 at ~100' fixed on Europe. For 80 meters there is a 4-square and a low inverted vee that is not useful in DX contests. Like me he has a shunt fed big tower on 160. He added wire parasitic elements that provide a small gain to the northeast and southwest. There are two reversible Beverages for receive.

That is a good complement of antennas. It is not equal to the biggest of big gun stations but well suited to the challenges of DX contests. Vlad turns in exemplary scores in single op contests. He's a better operator than I'll ever be.

Operating

We ran as much as we could. When the pile ups thinned we would click on stations in the band map or available mults & Q's window. Call them if they're there and then a one-key shortcut to return to the run frequency to resume CQing. I lost my run frequency only a handful of times, but you have to be quick.

Vlad and I frequently discussed openings, band changes, breaks, station passing, antenna use and direction. We could do this pretty effectively even while running pile ups. It may seem odd to watch us logging QSOs and talking at the same time.

Regular readers may recall that I often complain about errors by others copying my call. All those dits cause confusion. The most common error is VE3UN. I have since had that error removed from SCP (super check partial) but it doesn't seem to help all that much -- casual operators don't use SCP or forget to update the database, while others don't pay close attention. I had the thought that with so many dashes that VE3JM would be less prone to copy errors. Wrong!

Despite keeping my sending speed to 36 wpm and lower most of the time, errors were common. Typical examples were VE3MM (a fellow contester), VE3OM (dropped dit), VE3OO (?), VE2JM (VE2/VE3 confusion is common), and a few rarer mistakes. That's just how it goes -- there is no good solution. I suppose we should be happy that so many hams are active on CW, even if only on contest weekends. I  wonder whether they pay attention to the LCR (UBN) reports they receive.

Tangling in the pile ups highlighted a difference in technique among the big guns. Most stations click on the spot and toss in their call, big guns and little pistols alike. You might think that the big gun would win every time, yet they do not. Brute force only gets you so far. The sum total of the other callers may be as strong as or stronger than the big gun, or the QRM makes it impossible for the DX operator to separate one caller from the bedlam. 

I would evaluate the circumstances when my initial "brute force" call failed. I might recognize the call signs of other big (and bigger) guns or that the successful callers were in locations with more favourable paths. There are a couple of techniques to deal with the pile up. One is to call well off frequency, around 100 Hz, to make your signal uniquely distinguishable. The other is to call twice, hoping that the second call has less competition than the first. Don't do that if the DX operator is responding quickly because the added QRM slows everyone down! 

If neither works quickly there is the third option: go away and try again later. There are other stations to work and you don't want your rate to suffer. A few minutes later, after the big guns have moved on, go back and one call puts the mult in the log. These are lessons many little pistols have learned and that some big guns have forgetten.

Breaks

Yes, even with a great station you can run out of stations to work. As already mentioned, this is not the most popular of contests. The reason is that for many stations, North America is far away and difficult to work. Contests where everybody can work everybody will always draw more participants. That said, over 5600 contacts during a weekend with challenging propagation is not so bad.

Even with 5600 contacts spread over ~40 hours operating time is not as busy as it sounds. Consider that there were two run stations. That's like 80 hours for a single op or M/S entry. Divide 5600 by 80 and the average rate for each operator is only about one QSO per minute. The average is itself misleading since during the morning high band openings to Europe the rate can easily surpass 3 QSO per minutes per operator. The rate at other times can be painfully slow.

So, what to do? We hunted for stations and multipliers as much as we could, trying to keep an eye (or two) on the AMQ window (available multipliers and QSOs). Many of those required careful tactics and operator communication to pick suitable antennas, turn them if necessary and decide which station is best to chase a station based on the band change quota. For whatever reason, Vlad made many more band changes than I did, mostly because he was considerate about not interrupting my runs.

Yeet there were still dead times. We both took sleep breaks soon after European sunrise (after ~2 AM local time) when the low band rates plummeted and the high bands turned up little. During the afternoons, a quick break might be taken to get refreshed by doing something different, be it to check email, progress of the snow storm or to prepare and deliver food and drink to the other operator. One way or another we kept busy. But we took no sleep breaks other than a few hours overnight. We got up before sunrise to chase mults on the low bands.

Perhaps what was most frustrating were the poor rates when the propagation was quite good. You know it's good when the DX stations are loud but there are so few of them. Casual and only moderately serious contesters keep to a more human schedule for contests like ARRL DX. Tthat means regular sleep, meals and attending to their families and other responsibilities. They're in bed at 3 AM local time.

Taking a break at those times is not sacrilege. What you find is that the stations will still be there after the breaks. They want to work you and they will. Usually there would be a flurry of activity after breaks when we were newly spotted by the CW skimmers and by stations that had just "rotated" onto the band. After 5 or 10 minutes it was back to the grind.

Problems

Other than the problem of not enough operators, we had a few others. Some I've already touched on in this article, which I'll elaborate upon. They can be surprising.

Snow is precipitation, and therefore can cause precipitation static. Especially a major snowstorm accompanied by high winds. The upper yagis are most affected. The highest antennas on all bands from 40 to 10 meters were periodically unusable once the storm intensified on Saturday and continued through Sunday. We had to choose lower yagis. That wasn't too dreadful since there were fixed stacks to Europe on the 20, 15 and 10. It was unfortunate that on 40 meters we had to use the less effective XM240 rather than the Moxon. The Moxon is much smaller than my 3-element yagi but I was impressed by how well it worked.

As the saying goes: you can't work them if you can't hear them. It believe it is possible to select different receive and transmit antenna via the DXLog interface but for some reason we didn't do that. Perhaps that was an oversight on our part. I don't know the setup well enough to know for sure and I never thought to ask Vlad.

There was occasional severe interference between the stations. I don't know if it the Flex station was responsible or if it was the K3 receiver. Both have a pretty good reputation. The towers at Vlad's station are closer together than in mine, which might have had an impact. I know the VA6AM high power BPF work well, as do the triplexers. When one of us accidentally chose a run frequency half that of the other station it was easy enough to move. It's a common problem on CW; for example, 7.002 MHz and 14.004 MHz. It happens far less often on SSB since the phone band segments are mostly not harmonically related.

We didn't self spot, which is permitted in ARRL contests, even for unassisted entries. Many casual operators solely rely on human spots so this might have helped raise our score.

At the height of the snowstorm the lights flickered quite often. We crossed our fingers and hoped that the power would not go it. When it happened we'd exchange worried looks. Luckily the electrical supply held up. That was one big problem we escaped! You just never know with distribution networks in low density farm country, even though the grid is well maintained.

Results

Vlad had the online scoreboard on his screen but I didn't bother. The only page I had open was the space weather dashboard. When the going was slow and I was curious I'd ask him how we were doing. Mostly we were tracking our usual close competitors at VA2WA. With more operators they kept ahead of us though the margin was small. 

In the end we had about the same number of multipliers as VA2WA and they had 4% more QSOs. That's not bad for two operator M/2. Had activity been higher or the propagation better, their advantage would have been greater. Maybe I shouldn't complain so much about the poor propagation since it may have helped us. It'll be interesting to see whether errors change the comparison after log checking.

I pulled the following from Vlad's submission to 3830:

Call: VE3JM
Operator(s): VE3JM VE3VN
Station: VE3JM

Class: M/2 HP
QTH:
Operating Time (hrs): 40:50

Summary:
 Band  QSOs  Mults
-------------------
  160:  110    49
   80:  612    81
   40: 1156   105
   20: 1154   114
   15: 1445   117
   10: 1138   112
-------------------
Total: 5615   578  Total Score = 9,660,114

Again, complain as I might, we did pretty well. The multipliers were there and we worked almost all that we could. Mostly we lost out on those in Asia on paths through the auroral zone. DXCC on 4 bands is quite good, as is the large number of mults on 160 and 80. I didn't expect to work nearly so many on 160. Vlad worked most of those, even running Europeans at intervals when signal levels peaked.

Last year we scored over 13 million points, and other stations had similar results.

The storm continued after the contest ended so we both spent the night at the station. In the morning, Vlad dug us out when his neighbour had tractor trouble and couldn't help. Typical for Canada, the roads were quickly plowed and we were both on our way, Vlad heading west to Ottawa while I drove east to resume my familial obligations. 

When I arrived home in the evening I only had the time and energy to clear enough of the driveway to get my car off the road. Then I slept. A lot. The rest of my 100 meter long driveway had to wait for another day.

VA6AM Switchable 6-Band BPF

I have mentioned building and using these low power BPF (band pass filters) over the past several years. What I haven't done was discuss the BPF themselves. I didn't want to do so until VA6AM fully productized the BPF for sale. 

He's a busy guy, it is not high priority and so it may never happen. Since these are good products I decided to not wait any longer. I will do a deep dive into it in this article.

The 6-band BPF units are kits. That is, the individual filters are kits, the relay boards come bare, while the enclosure, connections and controls require fabrication by the kit builder. 

Pavel makes it easy to order the parts since he created a project on one of the major electronics distributors for ordering the parts. I doubled the quantities and ordered a few extras of some parts. I am not linking to the project since it may no longer be current. I built my units in 2021.

The kit is not the same as purchasing his low power BPF kits for the 6 contest bands: 160, 80, 40, 20, 15 and 10 meters. There are differences:

• PCB for the filters are narrower so that they fit into a not too large enclosure.
• Relay boards, including bypass relays, run on both sides of the BPF PCBs.
• The control board design is incomplete and not available. You have to develop your own control system, whether manual or automatic.
• There are interactions between BPF and via to the relay boards that the design addresses but had to be experimentally dealt with to optimize performance.

There are numerous commercial 6-band low power BPF products that I could have bought to avoid the challenge and difficulty of build these "kits". These are my reasons for not choosing from among them:

• Cost: High performance commercial units would have cost at least $2000 (for two). I spent about 35% of that to build my own, and they measure better than most. Although most of the saving was eaten by the purchase of the VNWA3 by DG8SAQ, I've used it for so many other projects so that it isn't a direct cost. An inexpensive NanoVNA can also do the job but not as well. I borrowed a friend's before taking the more expensive route.
• Learning: Everything from winding toroids, precise and accurate measurements with a VNA, filter tuning, designing control circuitry, and so much more. I love to learn new things and there was much to learn and skills to master.
• Accomplishment: Just as for towers and antennas, I like the challenge and accomplishment of completing a difficult task and seeing the results on the air. 

I understand that few contesters would make the same choice. They would rather assemble the station using commercial products and get on with the business of operating. Both are equally valid options. I did what I judged was best for me. I have no regrets, but it was a major undertaking.

What you get

The "kit" is comprised of two each of the BPF kits and sets of relay boards from VA6AM. You supply the parts for the relay boards, enclosures, connectors, hardware, wiring and control systems. 

Should Pavel decide to make this a product there will be revisions based on our experience with my prototypes. We both learned from the experience. Pavel was very generous with his time for the several months I spent on the project. He also shipped extra parts for me to experiment and improve performance.

Pavel had not completed design of the control board so I developed my own solution. My simple solution was probably better for me in any case. An 8-position rotary switch is used to manual selection one of the 6 BPF, BPF bypass and automatic band switching via my custom antenna selection software and hardware. 

Toroids

There are a lot of toroid coils in these BPF! There are 4 on each BPF for 160 through 15 meters, totalling 20, each with 2 interleaved windings, and double that for two units; solenoid coils are used on 10 meters. I've wound small toroids many times, however it is more difficult to do it well with heavy gauge stiff wire. This chore was probably the most difficult part of the project.

On the left is a toroid built by VA6AM. It's nearly perfect. My first attempt is on the right. That is not so good. Luckily the performance impact of ugly toroid windings is small. Perhaps the biggest risk is excess wire length due to loose winding which increases the inductance. I tried various winding techniques (Pavel made good suggestions) so that my toroids improved over time. 

There was no need to go back and redo the earliest ones since they could be adjusted to the required resonance. Indeed, toroid adjustment is, in all cases, done by compressing/expanding windings. It fussy work that is mystifying at first and soon becomes routine.

Construction and tuning

The input and output LC resonant circuits are tuned using a VNA or (less accurately) an antenna analyzer. The objective is to make both equal. A home built VNA probe is shown in use. I found that the 1 kΩ resistor at the end of the VNWA transmit port worked very well. It was suggested by Pavel.

Another common probe is a loosely coupled one turn coil passing through the toroid. It is important not to have the measuring system couple so strongly that circuit resonance is affected.

After each BPF is completed, both ends are connected to the VNA to measure port impedance and insertion loss. For the first BPF I temporarily soldered on BNC connectors (see earlier picture). Using wires is not recommended since they add inductive reactance that will not be present in the final product. The tuning will be incorrect and may be impossible to achieve. These filters are precision devices. The kits come with testing and tuning instructions.

Knowing little about filter design, there were curiosities during the tuning and measurement process. For example, I was convinced that the 40 meter BPF wasn't working properly because the lower band notch was on the high side of the desired pass band on 80 meters. Pavel explained that is expected since for Cauer filters that results in the best rejection across the 3.5 to 3.8 MHz segment typically used in contests. His explanation alleviated my concern, and in use it isn't an issue.

Another was the insertion loss on 15 and 10 meters. It was difficult to get the insertion loss below 0.5 db while also keeping the port SWR close to 1. Pavel tried to explain the reasons but I have to admit I still don't understand. 

It was to reduce the insertion loss that he switched to solenoid coils for the 10 meter BPF. He considered using solenoid coils for the 15 meter BPF but that increases the risk of interaction with the 10 meter BPF that also uses solenoid coils. 

The complete set of VNA plots can be found below. You can see a glitch on 10 meters for the 15 meter BPF. From additional testing per Pavel's direction it appears to be due to capacitive coupling via the relay boards, possibly between relay contacts and contact wiring. We did a test to ensure that is was not due to direct coupling to the solenoid coils on the 10 meter filter.

Visible in the picture of the 10 meter BPF at right are the back panel connectors and bypass circuit. There are UHF connectors for the input and output, 12 VDC power and a DB9 for automatic switching (not yet wired when the picture was taken). 

Pavel noted that the filters are symmetric so the connections can be swapped, however it is not unusual for one permutation to give slightly better performance. In that case it is best to label the connectors as radio and antenna (or amp) and always use them that way. The difference is negligible for my units so I didn't add labels.

Performance

Ordering of the BPF affects performance. 10 meters is closest to the connectors and 160 meters is at the other end of the enclosure. Although the relay board traces mimic a transmission line, they are not perfect and there are the deviations via the relays to consider. The primarily stray inductance is why 10 and 160 meter BPF are placed where they are. 

The BPF for the other bands are interspersed so that none is next to that of its second harmonic. For example, don't place 40 and 80 meter BPF next to each other.

Final tuning of every BPF must be done with the full unit assembled in the enclosure and the cover in place. It is also necessary that wiring of the control system (manual or automatic) is complete and functioning.

Another subtlety that affects performance is the soldering of wires from the BPF to the relay PCB. There is a ground connection via the metal stand offs to the enclosure bottom that should not be solely relied upon. One or (better) two short wires should bridge the ground strips at the PCB edges. 

The bypass circuit is simple enough, with relays and a short length of RG58. It isn't quite that simple since there is, again, stray inductance. The usual method to alleviate the problem is to place a shunt capacitor at one end of the coax. I experimented and got my best result with a 10 pf capacitor on one unit and (if I recall correctly) 8 pf on the other.

The VNA plots show the difference -- you may have to click on the picture to read the numbers. The scales are different but the marker data tell the story. It is easy to tell which plots are before and after the correction. 

The reason this works is that the shunt C and stray series L form an L-network that transforms away the stray inductance. That also changes R but only very slightly for the small amount of compensation required. The same technique is used in wide bandwidth T-bias and other circuits, and I used it to good effect in my stack switches.

The picture shows the shunt capacitor on the bypass circuit (top left). It also shows another on the 15 meter BPF (lower left). I found that I could slightly improve the insertion loss SWR with it. That was possible on 15 meters but not on 10. Since the explanation is a little esoteric and I don't fully understand it, I will say no more. 

Pavel was surprised that it worked and understood full well why it cannot be a general solution. It was an accidental yet successful experiment based on my measurements of R and X in this unique case.

I think I've given more than enough detail about how I built and tuned these units, indeed more than most readers want to know! I thought it worth taking the time since the details are quite fascinating to me. Designing filters with such excellent performance is well beyond my ability. All I can do is marvel at what is possible.

If you are in the majority of contesters that use commercial units or a set of high power BPF (VA6AM's are excellent as well), you might now understand more about what goes on "under the hood". Those who haven't read this far, well, I guess you'd rather not know.

The following plots for each band are for one of the units. The plots for the other are almost identical. That's a good indicator that small construction differences have little impact on performance. Careful kit builders should be able to achieve similar performance. As before, click on each picture (there are 3) if they are not readable in your browser.

4 years later

Despite my praise, it has to be said that these devices are not pretty. I could have painted the bare aluminum enclosures, added LED indicators, used a modern knob and added professional looking labels. I didn't see the point since I only touch the units twice in each contest: to switch it to automatic mode at the start back to bypass at the end -- they're in line full time. My preference (as it is for other contesters) is to get them of the operating desk. They are just clutter during contests, even attractive commercial products.

It seems a shame to do this after all the work put into this project. That's how it goes. I also don't need to see patch panels, rotators, antenna switches and all the rest of the station while I'm operating. The desktop looks tidier compared to the last time I showed a picture of it.

Low power BPF are not the highest performance solution to inter-station interference (SO2R, M/2, M/S, M/M). High power BPF are superior. However, that's a much more expensive solution and you can't easily carry them with you to other stations as a guest operator. Harmonic stubs are a good complement to low power BPF to deal with harmonics and spurious emissions from amplifiers. Construction, tuning and placement determine their performance.

Of course you don't need high power BPF if you operate low power or QRP. Low power BPF are sufficient in the majority of cases -- VA6AM low power BPF are good for 100 watts if the SWR is not excessive. I've done QRP contests without any BPF. You just need to avoid frequencies close to the other's station's harmonics.

In closing, I am very happy with these 6-band low power BPF kits. I've been using them for almost 4 years and I am not tempted to upgrade to high power BPF. It's a shame that they are not real products, and may never be. I was the first customer and it is entirely possible that I still have the only ones in active use.