Getting Better In Contests

We have comfort zones. You can easily recognize yours when you venture outside its boundaries. It can happen by accident or by design. It's uncomfortable. But if your intent is to change, improve, excel, you must do it. 

Stay in your comfort zone and nothing will ever change. Many rationalize why nothing in their lives improves, blaming government, other people, or circumstance. While all may be true in select cases, the jailers who keep us inside those comfort zones are ourselves.

Although the topic of this article is radio contesting, it applies to every aspect of life. It would be surprising were it not so. How did a runner get so fast? By running that fast, and doing the preparation necessary to make it possible. How did that fellow become a millionaire? Discovering what people want and then building a business to deliver it at a profit.

Both come with risk. There is no assurance that a desire to run fast is enough. There are barriers to success: injury, individual biochemistry, opportunity cost and more. Similarly for the prospective businessman: misunderstanding the market and competition, upfront costs (finances) and execution detail. But if you don't try you will certainly not succeed. Most people prefer their comfortable ruts to taking risks.

Do you want to be a better contester? What's your motivation? Are you willing to invest the time and effort and, yes, money? What does success mean to you: overall champion, local record, or simply enjoyment of the endeavour? Only you can decide.

For example, I enjoy contesting. Would I like to win? Yes. Will I? No. Does it matter? No.

For me the true enjoyment comes from building a competitive station and striving to be worthy of it. That is, to be better, not the best. In many ways I get more enjoyment from watching others operate my station. I'll never be a contesting champion or truly competitive yet I still enjoy the activity. I think that applies to almost everyone you contact in any contest. The elite are a small minority.

In a contest there are no class boundaries. Everyone works everyone and appreciates every contact. When there are serial numbers in the exchange you may be startled by what you hear. In the recent CQ WPX CW contest, after the first 30 minutes when I had almost 60 contacts I worked a top contester that sent me a serial number over 100. Impressive. The online scoreboard is an even better way to follow the top competitors as you pursue your own objectives.

Can you be a top contester? Probably not. However you won't know if you don't try. Yes, talent is required in addition to hard work. The first is out of your control but you are fully in control of the second. You may actually have the talent but haven't discovered it since you have not tried. The answer: try. You may surprise yourself. 

But talent or no talent, hard work is not optional. So let's talk about that. What hard work is necessary?

First up are the basic skill sets:

• BIC (butt in chair): You have to put in the time. Not just the contest but also preparation. Practice is essential. I'll make what should be an obvious observation: couch potatoes never medal at the Olympics. Get active, be active, stay active.
• Technical skill: Is your CW slow? Get faster. You do that by being active. Make QSOs, chat to people on CW. It isn't contesting and that's why it helps. You don't know what the other person will say or whether you can say what you want to say. Do you avoid some words because they're difficult to send? "Best wishes" is a good example because of all those dots in the second word!

It continues to astonish me how many long-time contesters, not just those new to radiosport, deceive themselves about these points. Be honest with yourself. Compare your operating and results with the best, not with your friends. That is, unless your friends have just won WRTC.

Observe, listen and learn

Choose a contest you don't plan to operate, find those top competitors and listen to them. I mean, not for a minute or two, but for an hour or two hours, or even more. If they're doing 2BSIQ, find them on the second band and listen to them on both receivers. 

I guarantee that you'll learn a lot from intelligent observation. Think about what they're doing, how they're doing it and why they're operating as they are. You will learn something. For example, I am regularly amazed by how the best operators can almost unerringly pick one full call from an unruly pile up, and do it on two radios. Not needing to ask for fills of calls and exchanges turbocharges the rate.

A friend of mine will travel to WRTC in July. He'll be a referee, not a competitor. Former referees I've spoken to have marvelled at what it's like to closely observe the world's best contesters in action. Not just during the 24 hours of the contest, also their set up, preparation and the team's post-contest discussion. Observe, listen and learn.

Join a multi-op and watch others operate and discuss tactics. Ask questions. You'll learn more in 2 days than you will operating multiple contests as a single op. However, only do it once you have some contesting experience or the flood of knowledge wash over you with very little sticking. Learning has to come in stages since there is only so much you can absorb in a short period of time.

Reject tradition

Humans are creatures of habit. We absorb the culture in which we're immersed and we are loathe to change our habits as we grow older. We my call it "tradition" to justify our resistance to change. But that's just a word, an excuse. Refusing change by clinging to tradition will hold you back, not just in contesting but in all aspects of life. Get over it.

Digital isn't traditional: too bad, get over yourself. AI-generated messages aren't traditional: too bad, get over it. Conversation on the ham bands is traditional: in a contest that's anathema (see below), so get over it.

Observe yourself. Every time you refuse a technology or an operating behavious because it isn't traditional, or what you're accustomed to, you are tying yourself down. You will fail to improve your contest results. However, if tradition is more important to you, accept the implications and don't try to blame others or claim that the world (or our hobby) is moving in the wrong direction. The limitation is within yourself, your clinging to "tradition". Reject tradition and become a more successful contester.

Accuracy vs. speed

Many contesters don't worry about their accuracy and some never review it when the final results are published. They may ignore their LCR (log check report) entirely. This may be surprising since the penalties from making mistakes can be quite onerous on one's score. From my experience this is because the vast majority of contesters are not competitive and they know it, doing it for the fun of it and to contribute to their club score. Fair enough.

If you care about your score you must care about your logging accuracy. How accurate should your logging be? What is a sensible objective? Should a higher error rate be acceptable when doing SO2R or for contests with variable exchanges (e.g. serial numbers) or complicated exchanges (e.g. ARRL Sweepstakes, or WAE QTC)?

I will propose a sensible target: 1%, for all contests no matter your category or contest exchange. Anything higher signals a need for improvement. Complex exchange or weak signals? Adjust your operating to compensate and still meet that accuracy objective. No excuses.

This objective is well beyond what most contesters can regularly achieve, whether novice or expert. It astonishes me how many supposedly serious contesters avoid talk about accuracy or convince themselves that 2, 3 or 4%, and even more (!) is perfectly acceptable. They can give you any number of excuses. Don't deceive yourself: excuses are unacceptable.

I don't really enjoy going through LCRs after a major contest. It's a lesson in humility. For example, in January's NAQP CW when I chose to focus almost exclusively on 2BSIQ my error rate was 2.4%. I'm not happy about it and I have to think about what I got wrong; I expected an error rate no more than 1.5%. Being a weak 2BSIQ op is not an acceptable excuse. 

If I have to slow down to avoid errors that's what I should have done. Accuracy always take precedence over speed. Too many contesters, novice and old timer alike, value speed over accuracy when the run is hot. That's a mistake.

"You don't get fast by training slow"

Those that know me well, know that my other great passion is cycling. In my prime I did well as a recreational rider, and I still get on the roads as often as I can. Of course I'm slower and can't go as far now that I'm old, but I still enjoy it. I was never competitive. Even so I strove to improve. 

I pushed myself, training with the strongest local riders, occasionally with elite athletes, and set high objectives on my solo training rides. I did the same as a runner, regularly doing interval training, and generally making myself miserable on a schedule. I did it because it got results.

I don't recall the source of the quotation I used as the title for this section. It applies to any athletic endeavour, and it also applies to radiosport. There are times when it is beneficial to train slow and times to train fast. However it is certain that if you never train fast you will not be fast on the day of the race.

You must push yourself, no matter your age or fitness level, if you want to get faster and score higher. No supplement, sleep schedule or other brand of magic will do it. Don't deceive yourself: getting better is hard work. You probably won't like it, though you will like the results.

Beginning contesters make many mistakes, which is to be expected and nothing to be ashamed of. Often those mistakes are passed on from mentors who have no track record of success. They're just trying to be helpful. Here are few of those mistakes:

• Participation in minor, low-pressure contests or those that are explicitly devoted to newcomers: While very accommodating, don't stay there since you're only going to hold yourself back. You need to mix it up with experienced contesters to challenge yourself. Don't extend your stay in the wading pool when your objective is to swim with the dolphins.
• Sending CW no faster than you are comfortable receiving: I can't tell you how often I've observed this perplexing behaviour. I can't understand it. If the other station is sending at 40 wpm why are you sending to them at 20? They can copy 40, so you are just wasting their time and yours. You already know their call and exchange (maybe you've had to listen to them for a minute to copy it at their high speed) so you're ready to go. Send fast! When I get called by a slow caller and a fast caller, guess which one I respond to? Time is of the essence. 
• Avoiding the low bands: They're noisy and effective antennas are challenging, but they're a gold mine of contacts and multipliers. Sure, copying is a challenge and your rate will be slower. So what? Every QSO boosts your score. In the coming solar minimum you'll work little if you avoid the low bands.
• Not calling the speedsters: Are you uncomfortable calling the big guns with a high rate and a high speed. Nonsense! Call them! Trust me, they want you in the log. Crank up the keyer speed on CW or crisply speak your call, once, using standard international phonetics on phone. Bashfulness is cute in a child, not in a contester.
• Unnecessary repetition: Send your call and exchange once. Repeat only when requested. You may have difficulty copying at one go, but experienced contesters will copy you fine. Repetition when it isn't necessary wastes everyone's time.
• Excessive time spent chasing mults: If you can't get through a pile up quickly or the propagation isn't in your favour, mark it in your band map and move on. You can come back later. There are other mults and contacts you are failing to log by fruitless calling. It's a contest, not a DXCC or WAS pursuit. Focus on your score, not the rarity of each station.
• Not running: You'll never be competitive in a contest by strictly calling others (S & P). Many contest novices or those with small stations avoid running. It's difficult! You have to squeeze yourself into a slot on a crowded band, pull calls from a crowd of callers, and deal with the pressure of not keeping callers waiting. Practice! Soon you'll marvel at how quickly your log fills up.

Set an objective and make a plan

As the saying goes: if you don't know where you're going, you're sure to get there. There is nothing wrong with entering a contest with no plan or objective and simply enjoying the experience. That stops being effective when you want to do well. Maybe it's to beat last year's score, beat a friend's score, work every multiplier, exceed 5000 contacts, break a record, or to win overall. 

Assuming the objective is within reason considering your unique situation, you are more likely to succeed with a plan. But what does a plan entail?

Reviewing logs can tell you a lot, be it just your own from last year or those of operators you wish to emulate. An increasing number of contests have public logs. Otherwise, if you know the individual you can ask, perhaps make a trade. Although propagation and other factors are never the same from year to year, there will be many similarities. History doesn't repeat but it rhymes.

Did you miss a band opening? Perhaps 10 meters briefly opened between 2 and 3 PM, or 20 meters opened overnight to Europe, or a mult was worked (missed) on 80 meters during their sunrise opening. Were runs better high or low in the band? When does 15 meters open to east Asia and Japan? These are just a few ideas I regularly deal with, and I'm sure you will have your own. 

Write the key points on a sheet of paper so that you do the right thing at the right time. Don't get so wrapped up in that big run that you miss 20 multipliers during an all too brief opening on another band. The run can be resumed later and the stations you didn't work will still find you.

To be honest, I'm not very good at making and keeping to a plan. I contest more for enjoyment than to accomplish a serious objective. The few times I do set an objective, that's when I make a plan.

Extraneous or pointless information

Many non-contesters have a poor opinion of contests and contesters. They listen to the pandemonium during major contest weekends and wonder why we do it. They criticize the seeming lack of meaningful conversation. To them we appear toxic, extreme and anti-social. For similar reasons, many will look at marathon running as boring, repetitive, unhealthy and also anti-social. 

Yet the participants in both activities (sports) are driven, committed and goal oriented. Yet outside of the events are talkative, friendly and ready to welcome and help newcomers to the sport. You learn little of a contester's (or marathoner's) social life by what you hear during the competition. The social interaction happens outside of the activity where the non-contester doesn't see it.

It is entirely natural that hams new to contesting, or perpetual casual participants, aren't so "lean and mean". They are more openly friendly on each QSO, say "thank you" and "please copy", among other statements that are extraneous to the basic data that must be logged. That's okay, but it's not compatible with a competitive result. To competitors the non-essential items, the unnecessary repetition of calls and exchanges, real signal reports and being greeted with their names (logger linked to QRZ.com) only slow them down. 

Sensible competitors adjust to it, as they must, since points are points and they appreciate every caller and every QSO. It's simply a part of the environment they must navigate. There are SO2R techniques, for example, to extend or delay on the second radio while a QSO drags on for longer than it strictly needs to be.

It is common on CW that even best friends say nothing at all when they work each other in a contest. For social human beings this behaviour feels wrong. Yet it is perfectly acceptable and may be necessary when juggling QSOs on two radios. On phone it' may be easier to drop in a "hi Joe" before smashing the keyboard to send the pre-programmed exchange. Even this may be lost as AI continues to eat away at phone contesting.

As a competitive contester you want to be polite while avoiding non-essential communication. You should tolerate it in your QSO partners, but don't do it yourself. Save the chatting for after the contest. You're in a race, you can stop to smell the flowers later. If saying something doesn't contribute to your score, don't say it. That isn't rude, and you should not feel guilty doing it.

Other considerations when you're running: never say "QRZ?" since it conveys nothing; listeners know that you just ended one QSO and you're going on to the next. Give your call instead since that tells listeners who you are. Only repeat calls and exchanges when conditions require it or on request. Again, if it doesn't contribute to your score, cut it out! Don't repeat back the other station's exchange, they already know what they sent. If you're uncertain, request a repeat.

There are far more poor practices than I could possibly list, so listen to yourself and others and make your own judgments. Many of the best contesters record the whole thing and play it back later to see how they sound, or to review mistakes reported in the LCR.

Trust others and be courteous

A good contester is a courteous contester, both to fellow contesters and others sharing the band. This is not about proper social mores, as important as that is. Conflict is fatiguing and will lower your score. Keep your emotions in check.

Place your trust in your fellow competitors. Those out to cause you pain are a small minority.  When trouble arises you should first assume good intentions. For example, a station appears to muscle in on your run frequency. Maybe they don't hear you or failed to check the frequency properly. Don't lose your temper. Tell them and in a majority of cases they will move. If they don't move and the tactic is deliberate, it is better to QSY and continue your run elsewhere. There is a lot of spectrum and getting into a battle will hurt your score. Try to see the big picture at all times.

When you are called by someone not quite clear on what a contest is or what you need from them, take a moment to explain. After the QSO, thank them for the points and encourage them to call others. You are helping to increase activity in future contests, which we want. If you are rude or exasperated at their ignorance you will lose points and turn one more ham against radiosport. Courtesy pays dividends, rudeness will come back to haunt you.

Yes, it's a competition, but never lose control of your emotions. Relax. Take a break if you're becoming short tempered or frustrated.

"It never gets easier, you just go faster"

This is a quote by Greg Lemond, a very successful professional cyclist. It was supposedly said in response to a journalist asking him whether racing was less difficult as he became stronger. You always perform at your limit whether as a youthful amateur or a world champion. Your competitors are doing the same. Experts at their craft may make what they do look easy, but it isn't. When you ease off the accelerator, you slow down and you lose.

When you do everything right and your contesting skill improves, your scores will improve. But it will not be easier. You'll be able to do more at the same perceived level of effort. There is a joy of being facile at 2BSIQ, madly typing on two keyboards and copying without error, yet it is hard work and you'll be doing it for hours on end. Talk to any contest winner and you can be sure they won't tell you that it was easy!

Be honest with yourself

There are few champions, almost by definition. If everyone's a winner, no one's a winner. A pyramid has one peak. I am not a champion and neither is almost everybody reading this. Maybe you can be one someday, or maybe not. You practice, you build, you compete, and keep improving.

Learn to appreciate the journey, not only the destination, and you'll suffer fewer disappointments. You don't have to be a champion to be a winner, to derive great satisfaction from radiosport. Contest champions are not necessarily happier than the rest of us.

Self-deception leads to frustration, dissatisfaction and scapegoating. While it's okay not to be champion no one wants to hear you casting blame elsewhere. I accept my limits. I can still learn and improve, open my station to others and find other ways to enjoy radiosport. 

Without honesty, how can we be open to improvement? There is always more to learn.

6 Meters is (Temporarily) Dead

The summer solstice is the peak of the sporadic E season. However, that is a probability, not a certainty. We don't have any reliable models for predicting sporadic E propagation so all that we can do is watchful waiting. Although unusual for this time of year, this is what 50.313 MHz looks like this morning.

It's largely been like this for the past week. Okay, I am exaggerating, but only a little. I have heard at least one DX station every day, if only one or two stations. There has been little workable since the openings have been brief and weak. Mostly all I see on the screen all day, every day, are the optimists (CQ DX) and the robots. I filter most of the latter. I am happy to hear the CQ DXers since those east of me in VE1 and W1 and those south (W3 and W4) regularly copy DX stations before I do as conditions ramp up in the early morning.

There has been only one widespread European opening this year. There have been many marginal openings to Asia (east and west Asia), Africa and Pacific (New Zealand and Hawaii), but little that put contacts in my log. I have one new country (thank you OD5VJ) and almost logged A7.

So we sit and we wait. Probability is like that. The band is barren this week but it could be wide open every day next week. There's no good way to know. Magic on the magic band is whimsical. Elsewhere in the northern hemisphere the propagation on 6 has been better, but not by much. Often when I check the global spotting networks there is nothing being heard on 6 anywhere. The temporary absence of propagation is global.

You would think this would leave more time for blogging, but it is not so! Summer has many distractions. In a way, this article is more about letting you know that the blog is alive than that 6 meters is barren. Here's hoping for better days ahead.

One final note about GridTracker. A friend encouraged me to give this tool a try. So I installed it and found a few uses for it. Although I don't chase grids I've found that it provides a very useful graphical view of developing 6 meter conditions by linking it to WSJT-X for live tracking of what my station is hearing.

In this snapshot there is an abundance of activity on 50.313 MHz. It is very difficult and time consuming to watch the scrolling messages on the decode pane. So I put GridTracker on top. There is a limited sporadic E opening to France and Spain (those are common from this region) and a line of US stations almost exactly to the west. You can tell where the ionization patches support propagation of signals.

More recently there was a similar line that gradually extended to the southwest, encompassing W6 and XE stations with strong signals. A few minutes later ZL1RS and ZL1SG popped out of the noise, when GridTracker "painted" their grids on New Zealand's north island. They are on the exact same bearing as those North American stations. We had a similar opening to KH6 develop from a westerly line similar to that on the screenshot

The graphical presentation of signals is superior for tracking developing sporadic E conditions. I can sit at my usual (non-ham) computer doing work and occasionally glance over my shoulder at the GridTracker window on the shack computer to stay abreast of conditions. If you remote your desktop you can do the same from your phone.

This may not be how most hams use GridTracker, but that's how I use it. It installs easily and automatically taps into WSJT-X. All software should be this easy to use and configure. If you are a 6 meter enthusiast you could benefit from this application, just as I have. Perhaps you already do and I've been slow to embrace it.

Mirror Yagi - Unconventional Reversing

Directional antennas require a way to change the direction if they are to be useful for most operating. Methods include:

• Mechanical: rotators
• Mechanical: element reconfiguration (e.g. Steppir)
• Electrical: switchable multi-element arrays such as 4-squares and vertical yagis
• Electrical: reversing arrays such as end-fire, reversible yagis, etc.
• Bulk: multiple uni-directional antennas

Many contesters have chosen to forego rotators entirely since they can be unreliable and difficult to service. However, installing a multitude of towers and antennas to compensate can be expensive. Electrically switched arrays can be an effective alternative. I have covered some of these in my blog, and information on all types of these arrays can be found in the literature:

• Low band 4-squares and vertical yagis
• Directional reversible receive antennas such as Beverages
• Reversible yagis where the role of each element changes (e.g. interchanging directors and reflectors)
• Reversible yagis where some elements are interchanged and others are fixed

The first two in the list are most often seen on the low bands -- 40, 80, 160 meters -- since they may be the only way to achieve effective directivity. The last two on the list can be fixed, such as reversible wire yagis, or rotatable, such as reversible conventional yagis. I have found reversible yagis on partially rotatable side mounts allow quick switching and almost full 360° compass coverage. 

For productive paths that are 180° apart, reversible wire yagis can be very effective. That works for us in eastern Canada with Europe to the northeast and the bulk of the US to the southwest. In the distant past I had an electrically reversible 2-element yagi for 40 meters that worked well for me during contests and at other times.

All those antennas alter the role of each element when electrically switched. For whatever reason, I was recently musing about the complexity of those arrangements and wondered if there is a simpler method. I came up with one that, although it works, is unlikely to be of broad interest. However the reason it works is sufficiently interesting that it is worth discussion.

It's what I'll call a mirror yagi since the two directions share a common reflector. The other elements are distinct. Switching directions is quite easy, only requiring selection of the driven element.

The question is how well it works. My first version was a 3 element yagi with 5 elements. That's a long boom for the lower bands but it can be quite reasonable at higher HF and at VHF. It could be particularly handy at VHF since it is routine to hunt for stations or openings at various compass directions. A lot of turning of yagis is can be eliminated.

I chose a 3-element model for 20 meters only because it is recent among my designs. The azimuth patterns of the original yagi and the mirror yagi in both directions are plotted above. It is no surprise that the mirror yagi's pattern is identical in both directions since it is fully symmetric. While these plots are for 14.150 MHz the similarity is present across the band.

The pattern of the original yagi is only negligibly different. It is interesting that the gain and F/B of the mirror yagi are slightly better. Yagis are complex antennas and they can surprise us at times. But practically speaking they are identical.

The same is true of the SWR. It is also nearly identical across the band, whether the mirror yagi is fed in the forward or reverse direction. The SWR curve for the original yagi can be seen in a previous article which I linked to above.

Before discussing the perhaps surprising results of this modelling experiment let's look at a conventional 2-element 20 meter yagi; again, yagis scale well to other bands so my choice isn't important, just convenient. This model has constant-diameter elements rather than tapered, but that also doesn't affect the results.

In this case there is noticable current on the reverse direction's driven element. This is visible in the above EZNEC plot of the element currents. That's significant, as will become evident when we inspect the patterns and SWR. Clearly something is different in comparison to the 3-element yagi.

The gain is only slightly worse on the 2-element mirror yagi. As expected, it is the same in both directions. F/B is better than the original 2-element yagi. These patterns are for mid-band, and there are similar differences at other frequencies. 

Whether these differences are significant depends on what one wants to achieve. It is certainly a simple antenna that is not too large, even on 20 meters. My interest is for an antenna that allows for easy checking of propagation in other directions without needing to rotate a yagi.

Unfortunately the SWR suffers greater degradation. This is likely to be a problem in most stations. The SWR bandwidth has narrowed significantly, and it is never all that good for 2-element yagis other than a Moxon. A mirror Moxon might eliminate the pattern and SWR differences from mirroring a conventional 2-element yagi. I did not do the experiment, at least not yet, since there are complications achieving mirror symmetry of such a Moxon. There is more to the design than simply adding a driven element for the reverse direction.

The F/B of conventional 2-element yagis is reasonably good only over a narrow bandwidth. Yagis with 3 or more elements do quite a lot better. For a mirror 2-element yagi the poor F/B help to explain their relatively poor performance: there is a strong enough field behind the reflector to couple to the mirror driven element and thus disturb the pattern and the impedance.

With a reasonably high F/B -- 10 to 15 db at a minimum -- mirroring should work well. We see the same thing when tuning a yagi by pointing it up, which we can do with the reflector only a modest height above ground since it doesn't "see" the ground. A greater height is needed with a 2-element yagi for ground coupling to be sufficiently attenuated. 

What about mirroring yagis with more than 3 elements? I expect that these will mirror the success (ha!) of the 3-element yagi. These larger yagis -- mirroring doubles the boom length -- rapidly become impractical due to the number of elements and long booms, even at VHF and UHF. I doubt that these are worth the trouble.

I am seriously contemplating a reversible 3-element yagi for 6 meters as a handy tool for checking propagation paths during sporadic E season when opening can be brief and unexpected. It would complement my usual antenna -- 6 elements at 24 meters -- and it isn't too large with a boom length of 4 meters and no rotator required. Not this year, but I'm thinking about it. 

Readers may be inspired by this article to come up with applications of mirror yagis that meet their unique requirements. It's one more tool in the antenna designer's toolbox.

Duty Cycle

With the return of sporadic E season on 6 meters my thoughts turn to transmitter duty cycle. That might seem odd unless you know that I almost exclusively operate digital modes on 6 meters. I have to monitor my use of the amplifiers more carefully than I do on CW and SSB. Most hams know that it is recommended to operate transmitters and amplifiers at lower power on digital modes, yet the understanding of why is perhaps lacking. Failure to reduce power has not gone well for many.

Despite so much written on the subject it seems worth another article on the subject. Will it help? I don't really know. Repetition has its own benefits and perhaps putting it all in one place will help a few readers. Or not. I'll try anyway.

Here are a couple of samples. On top is audio from a recorded wav file from one of my contest messages. There is no compression in the recording so the duty cycle is low; compression is added during transmission. On the bottom is a sample of CW keying. The duty cycle of the transmitted signal is slightly lower due to shaping: gradual rise and fall times to prevent key clicks.

Duty cycle for both CW and SSB can be exquisitely calculated, if you wish. That isn't necessary since we don't need that degree of precision. CW is approximately 50% when you average over dots and dashes, inter-character and inter-word spaces, and of course ordinary brief pauses. SSB can be less than 20% though few of us operate that way. Instead we equalize and compress the audio so that the duty cycle of SSB is also approximately 50%. In contrast, digital modes like FT8 and RTTY are 100%.

That is (literally) only half the story. We interleave receiving and transmitting. Assuming typical communication, conversation or contesting, we do both approximately equally. Therefore the transmit duty cycle is closer to 25% for CW and SSB and 50% for digital. FT8 transmit cycles are really only about 42% and if you CQ a lot without replies, the duty cycle for CW and SSB may be closer to 35%. Again, we can mostly ignore these nuances for the purpose of this discussion.

One problem with the basic definition of duty cycle is that it is a moving average that changes from moment to moment. For example, although a single phone QSO may have a 25% duty cycle, when averaged over, say, 1 hour of time in front of the radio, the duty cycle can be much less since you spend more time listening than in QSO.

Digital is similar. An FT8 transmission interval is 15 seconds, where you receive for 15 seconds and transmit for 15 seconds (actually only about 12.6 seconds). Over the course of a QSO the duty cycle is 50%, double that for CW and SSB. If you behave like a robot the 1 hour average may be the same, and therefore far higher than for CW and SSB outside of contests. That is one difference between digital and modes like CW and SSB where robots are, at least so far, absent. 

That 100% duty cycle is only when averaged within the bounds of a single transmission interval. Said another way, the instantaneous duty cycle during an FT8 transmission is 100%.

Up to this point I very much doubt that I've said anything that the majority of readers don't already know. From here I want to combine the idea of a moving average with transmitter and amplifier operating parameters. The connection between them is heat, more specifically heat transfer.

This is me operating on 6 meters FT8 with an Acom 1200S solid state amplifier. Notice the power level. I rarely go above 650 watts on FT8 since the temperature soon rises towards 70° C, the nominal limit. When the shack is warm the power must be kept below 500 watts. The reason is that input air is warmer and is less able to remove heat from the amplifier. On CW and SSB I regularly operate at a full kilowatt, where the lower duty cycle keeps the amp within its temperature limit.

In this stylized diagram we can see how the temperature rises during alternating transmit and receive cycles, light gray for FT* and dark for CW and SSB. Average power output is the same for both. Although the reality is a more complex, the diagram communicates the important ideas. Line width shows the variation based on ambient temperature: the hotter the air going into the amp the less effective the cooling system.

At first the temperature rise is sharp, with the slope gradually declining as the amp heats up. The slope declines (the lines really ought to be curves!) because of the increasing temperature difference between the incoming coolant fluid (ambient air) and the surface of the heat sink.

The red line is the temperature at which the amp protection trips. Operating with lower average power is required on FT8 to keep the temperature within the acceptable range. However, as you can see, it is possible to operate at higher power for a short period. Robot operators and contesters need to be more mindful of the long term average, and therefore the duty cycle.

Cooling effectiveness is a function of coolant heat capacity, ambient temperature, airflow volume, and the surface area of the material to be cooled. As is the case for any heat pump, the ability of the coolant to draw heat from the material increases with the temperature differential. Cool air cools better, and the hotter the material the more heat can be drawn off by the coolant.

At right is a picture I took of my Acom 1500 output air vent showing the integrated heat sink (cooling fins) of the 4CX1000A, the chimney directing air through the cooling fins and the exhaust air temperature sensor (top centre). 

In contrast, consider the picture that I pulled from the internet of an LDMOS device being bonded to an amplifier heat sink. We have more options on where to place the temperature sensor. It can be a thermocouple in the device, on the heat sink or a sensor placed in the airflow as is done for tube amps.

With respect to heat transfer, tubes like this have the advantage. Bonding of device elements to the heat sink is entirely integrated. The designer's job is to ensure that the air flow is properly routed and of sufficient volume to meet the cooling requirements. 

Glass envelope tubes are more challenging since there is a combination of conducted heat (bottom pins and top anode) and radiated heat from the interior metal components, especially the anode. Typically the air flow is from the bottom, to cool the pins and their glass seals, then around the glass envelope. Air flow is directed using vents and chimneys. The temperate sensor should always be at the exhaust.

Solid state devices are acutely sensitive to good thermal bonding since there is so much heat concentrated in a small volume and with limited surface area to conduct the heat away. For example, for 1000 watts of RF at 60% efficiency, the heat produced is 670 watts. That's a lot to transport over a few square centimeters of heat sink contact area! Once you get the heat over that barrier, cooling the heat sink is relatively easy.  

It is no surprise that LDMOS longevity is highly dependent on transferring that thermal load to the heat sink. Thermal protection must trigger quickly and reliably to protect the devices. The MTTF chart is from an old Freescale presentation on LDMOS. The device mentioned is likely obsolete now, however newer devices, like any semiconductor, will have similar thermal characteristics.

This brings us to the question of what we're actually measuring and where we're measuring the temperature.

All methods of thermal protection are by proxy. That is, we're measuring temperature at some remove from the locations where the heat is generated and the points of greatest criticality. Indeed, most amplifiers have more than one measurement system to detect thermal problems. For example, in a tetrode like the 4CX1000A the control grid has almost zero ability to dissipate heat. Exhaust air temperature won't detect that. It is necessary to monitor grid current and quickly shut down the amp when current indicates excess power dissipation (by P = I²R). 

Despite the sensitivity of the grids, overall tube temperature can be very high. It is common for me to measure a temperature of 90° C when continuously running ~1000 watts of FT8 on 6 meters during warm July days when the house air conditioning is off. That's enough to brew tea yet the thermal protection trigger is even higher.

LDMOS devices can quickly fail if the semiconductor junction temperatures exceed their limits. Unless there is a thermocouple built into the device we are limited to proxy measurements outside the device. 

Ideally it should be on the metal body or, if that isn't possible, on the heat sink near the LDMOS. Exhaust air measurement may be too far removed from where the heat is generated. Unlike a tube, a brief internal temperature spike may be unrecoverable. Remember that when you absolutely must work that new one.

Proxy measurements are dependent on good design and construction practices so that the thermal transfer from the interior to the heat sink is predictive of the junction temperatures. Unfortunately that is not always the case and the devices don't last for long. The screenshot is from a video by W8JI demonstrating poor thermal bonding of a FET in a late model Ameritron amplifier.

To quote the aforementioned Freescale presentation: LDMOS device thermal resistance benefits from having a backside source that is thermally and electrically bonded to the package flange, which in turn is directly mounted to the heat sink. Metal to metal contact is best. I've built power supplies and other projects where the power transistor requires a thin insulator between it and the heat sink, with thin coatings of toxic conductive paste to minimize thermal resistance. There is also the hazard of capacitance between the transistor case and the heat sink in RF applications.

It should be clear by now that thermal protection circuits on amplifiers, tube or solid state, require a physically removed sensor that measures by proxy, which demands excellent construction so that the proxy measurements are predictive of temperatures at the critical points. Otherwise we should expect regular and expensive repairs. 

In this context, duty cycle is really only one factor among many, and not necessarily the most important. Indeed, it can be expensively misleading. 

Increasing airflow (bigger and noisier fans) can only be effective if thermal transfer from device to heat sink meets the design specification. In this respect, solid state devices are more difficult to reliably cool than tubes. 

Although competent amplifier designers take these factors into account and incorporate thermal protection, failures can still occur. A little common sense on our part can pay dividends:

• Buy from companies with a reputation for good build quality, that stand behind their products and don't practice blame shifting when failures occur
• Device ratings and duty cycle matter less, often far less, than amplifier design and construction 
• Install equipment so that airflow is unconstrained even if the fans are annoying; many modern solid state amps can be operated remotely if it's a problem 
• More protection circuitry is better than less, despite the annoyance of false alarms 
• Understand that nothing is forever: failures will occur, even in expensive equipment 

I intend to follow my own advice when I buy my next amplifier, probably this summer. 

Modern Spotting

DX spotting clusters have existed for decades. Originally they were isolated systems accessible via packet radio on VHF or UHF, and therefore limited to the local community. Unless you already had the equipment it required time and money to get connected. The value was dependent on the size of the local DX community and their willingness to connect and spot what they heard.

We built an AX.25 VHF cluster in Ottawa almost 40 years ago. It didn't go well. There were too few of us, the node was difficult to reach (too far out of town) and spots were infrequent, mostly just evenings and weekends. After about a year the node was decommissioned and we donated the equipment to other local VHF projects that had nothing to do with DXing.

Today it's easy. PCs, smart phones and internet connectivity are universal. Pick an app or an internet DX node and you're ready. You can spot at the click of a mouse or do it automatically. You can receive spots from hams across the globe or just your region. There's so much traffic that it must be filtered to avoid being overwhelmed. Then there are the perpetual incompetent spotters and also the limited utility in knowing what DX stations across the ocean might be hearing and working.

Do you want to work the latest rare DXpedition? Chances are that they have a live stream where they post each station worked, including mode and frequency. That's the ultimate in self spotting behaviour. You don't even need to check for spots of these stations. Filling band slots and reaching DXCC Challenge endorsement levels has never been easier. Some think it demeans the value of DX awards, but most hams love it.

Nobody listens anymore. It's time to revisit the topic of DX spotting.

CW

When I tuned to 20 meter CW one afternoon this week there were no spots on the band map. Yet there were many signals visible on the transceiver's waterfall display. I enabled skimmer spots and within 10 minutes there were dozens of spots, only two of which weren't from a skimmer. I am careful to filter for skimmers located in northeast NA to reduce spots of stations I'm unlikely to hear.

CW skimmers work so well that most operators no longer bother with spotting. Whether that's good or bad is a matter of opinion. Skimmers make mistakes, including decoding errors and phantom signals. They may also have antennas too poor or too good to mimic a typical station. 

An increasing number of nodes are installing filters to weed out the problematic spots, whether human or skimmer generated. They're becoming quite good at it, often better than proficient CW ops -- typos are common. Skimmer spots don't include splits (for rare DX), and human split comments are frequently unreliable.

Even on 160 meters where I have excellent Beverage receive antennas there is little need to tune the band. There are skimmers with dedicated receive antennas that perform admirably. It is also useful for any weak station (e.g. QRP) since skimmers pay more attention to the weak ones than humans do. Once your weak signal is picked up by the skimmer you will attract callers, be it for POTA, in a contest, or other operating activity.

The technology has progressed to the point that, like many others, I rarely spot stations on CW, and I can do it without feeling guilty. One exception is rare DX that may rarely identify or not follow standard CQ pattern that might not be picked up by skimmers.

SSB

There are no phone skimmers, at least not yet. They'll come eventually but until then we are reliant on human spots. For those that rely on spots to find stations, rare DX or not, be aware that most stations do not spot the phone stations they hear or work. If you dislike spots and prefer to find stations yourself, this may be seen as unimportant or perhaps a positive. That is not a common view.

There is a way to increase phone spots. It remains largely a feature of contest logging applications such as N1MM Logger+. It is a simple configuration change with which every station you work by S & P (they run and you find them) is spotted, if you are connected to a DX cluster. 

While not mandatory it is recommended by many contesters. The objective is to increase the number of phone stations that are spotted to a level comparable to that achieved by CW skimmers. 

This is the best we can do until we have software that can reliably recover call signs and other critical spoken QSO data, whether in English or other languages. It's a challenging technical problem. My prediction is no less than 10 years until it is broadly available and sufficiently accurate. I could be wrong and we'll get there sooner, or much later! There is no financial incentive so we are dependent on technology developed in fields outside of amateur radio and, of course, dedicated and capable volunteers.

Digital

Digital modes are particularly amenable to automated spotting. It has been available for years through use of WSJT-X and similar apps in concert with services like PSK Reporter. One only needs to click a check box to report all that the software hears. The data can be retrieved and analyzed via online services, whether PSK Reporter itself or downstream services that utilize the data feed.

You can manually inspect what other reporting stations are hearing or use services that graphically present the data. Again, I am no expert on those services so I'll let you discover those on your own.

Even if you don't send your data to PSK Reporter, you will be found since most of the stations you work on digital modes upload their reception data. 

Contests

Spotting in contests is different. The major difference is that, for a big station like mine, you run most of the time. When you run you have nothing to spot. Not only that, the spots that do appear are less appealing. Certainly you want to chase multipliers and other contacts, but if you're in an assisted class you click on spots and so you have little to contribute to the community. That is, you are not spinning the VFO and spotting stations that are not already spotted.

If you operate unassisted you do not spot. It is true that some contests allow you to spot others but not see others' spots. However that's rarely done even when permitted by the rules. Operators just don't connect to DX clusters when they're not in an assisted class.

For an increasing number of contests it may be that most of your spots will be for yourself: self spotting, where the rules permit it. When you're running there's little else for you to spot. This benefits you and nobody else, but that's the nature of the game: you want to be found and others want to find you.

In CW contests the skimmers are so successful that I often turn skimmer spots off. The reason is that the flood of data is overwhelming and not necessarily useful. Early in a contest everyone is a new contact so the band map isn't needed. Later after many stations have been worked, I turn skimmer spots back on.

For the casual operator in a contest, you are more likely to be a consumer of spots rather than a producer. Considering the high activity level in contests that really isn't a problem -- you probably aren't adding anything that others, including skimmers, aren't already producing.

Tools

There are many tools to analyze spots in real time or near real time. Some are downloadable apps while others are web based. You can track DXpeditions, where and on which bands there are openings, get alerts for grids, countries and specific stations. Many are free. The data is also used for research, mostly amateur but some professional, to correlate with solar and geomagnetic data and refine prediction algorithms. With so many spot sources there is a lot of data available.

I've used a few of these tools though far less than many others. Since I am not in a position to make recommendations, I won't. You can find them and their champions through an internet search. I'll leave it to others to guide you if you want to pursue the topic.

Where we are

Like it or not, spotting is the way a large majority of hams find stations to work. Older hams may reminisce about the old days when we spent many evenings spinning the VFO looking for stations to work, or that elusive rare DX with an unpredictable operating pattern. Those days are gone and they are not going to return.

The truth is that all that VFO spinning was tedious and frequently fruitless. I recall the days when I left my 6 meter rig parked on 50.125 MHz during sporadic E season. The hiss of the receiver filled the house since squelch wouldn't trigger on weak signals. Don't try this if you're married or living with others! The discovery potential of FT8 and other digital modes is one reason it has large replaced CW and SSB as the mode of choice for the serious 6 meter DXer.

Skimmers do much the same for CW, discovering stations and rare openings that would otherwise be missed. Although there is less need to spin the dial, it is helpful to CQ into the aether from time to time for the skimmers to have something to copy. If nobody transmits the band is dead to humans and also to our automated listening devices. That at least hasn't changed.

6 Meters is Heating Up

It's said that sporadic E does better when solar activity is low, thus favouring the years surrounding the cycle minimum. With the solar flux falling maybe we'll get some fireworks this summer.

I've worked the first DX of the 2026 season. Nothing too exciting and nothing new, but that's to be expected with 150 DXCC entities worked on 6 meters; every new country is harder to work than the last. Of those, 140 are confirmed on LOTW, my only QSL route.

So far this May I've worked S0 and EA8. I've heard other countries including several in Europe, D2 and in the Caribbean and South America. Around the continent, I've worked stations in VE7 and W7 along with several stations closer in. I could work many more if I was interested in short haul contacts, which I'm not.

DX signals are weak and fleeting this early in the season. From PSK Reporter data I know that I've been heard in Europe. I have no contacts with Europe yet this year. The summer solstice, the usual peak of the sporadic E season, is still 6 weeks in the future. It will get better.

Despite the negativity often seen with regard to digital modes, 6 meter DXing is one place where FT8 shines. It is perfect for discovering and exploiting the brief intensification of ionization that transport signals between continents at VHF frequencies. You can't chat over FT8, and that's fine with me. I don't chat much over CW or SSB either since my interests strongly lean towards contests and DX chasing. I see no reason to have a conversation when 6 meter opens; I have other priorities.

To enhance my enjoyment this year I configured my station so that I can operate HF and 6 meters at the same time. My hope with this change is to catch openings earlier than I otherwise would. 

My usual SO2R contest setup is ideal for this. It's quite easy to do by moving the 6 meter antenna to the second radio (Icom 7600 & Acom 1200S) and using it with WSJT-X. The main radio (Icom 7610 & Acom 1500) is dedicated to HF. Both radios connect to the same PC, one using N1MM and the other using WSJT-X. 

To limit interference when I'm transmitting on either radio I switch in the contest band BPF on the 7610. I have no BPF for 6 meters. That will remain a low priority despite its potential benefits. I know fervent contesters that dedicate a radio and amp to 6 meters so that they can work sporadic E openings during contests. FT8 is easy to operate in parallel since it is slow and only requires the occasional click of the mouse. There are no audible distractions to the CW or SSB contest activity on the HF radio.

Although less powerful on high duty cycle digital, the solid state amp is near instant on versus the 3 minute warm up period of the tube amp. With such fleeting openings the rapid readiness of solid state is more important than another 1 to 2 db. I prefer not to keep the tube amp idling all day long, especially in summer when the shack is already too warm. When I buy another solid state amp later this year it will increase my flexibility, and power, in this activity and in contests.

Returning with the propagation are the 6 meter robots. They are growing in number. Unfortunately, WSJT-X-improved supports a blacklist of only up to 12 call signs. I wish it were larger. I find myself editing the list as robots appear to strike out the ones bothering me at that moment. It would be easier to add each of them once.

I don't really mind the existence of robots, I simply ignore them. The problem is that they fill the decode screen with their endless CQs that push the wanted DX signals off the messages received pane of WSJT-X. I have to scroll the screen to see what I might have missed. It is easier when I can just glance at the screen from across the room. So I filter them into invisibility. I find the behaviour of robot operators perplexing but it isn't my concern.

As always, don't be surprised or offended if I don't reply to you when I call CQ DX and you are not DX. It's nothing personal: you're not my intended audience. My primary interest on 6 meters is DX. I don't hunt grid squares, states or special call signs. One of the joys of amateur radio is that we can pursue our individual interests, together or separately, while sharing the same spectrum.

Enjoy the season. Soon the DX will be rolling in. If I get lucky a few new countries will fill my log this year. Working DX on 6 is enjoyable to me even if I work no new ones. I hope that you have success on 6 this season no matter your objectives or station size. If you've never given 6 meters a try, you should. Sporadic E season is the ideal time of year to take the plunge.

Another Rotatable Side Mount - 15 Meters

One lack in my station is a sufficiently strong signal on 15 meters into Asia, especially east Asia. While we cannot run Asian stations like our friends further west there is a rich vein of multipliers to be mined during major contests. I was reminded of this during the last All Asia SSB while running Japanese stations by how incredibly weak most were, barely a whisper above the noise. And this is from a quiet rural QTH.

The 5-element stack for 15 meters has a rotatable upper yagi at 43 meters and the lower yagi is fixed on Europe at 32 meters. Individually and together they are very effective antennas. In daily operating the stack can easily break pile ups with just 100 watts. To achieve stacking gain the lower yagi must become rotatable. That is never easy for side mounted antennas.

There are two possibilities: a swing gate or ring rotator for close to full 360° rotation, or a fixed side mount for about 130° of rotation. The first is not really necessary in my station since I have other yagis that can fill the gaps. It is also the more mechanically challenging of the alternatives. 

The latter method can work well if the 130° of rotation includes both Europe and east Asia. That I can do. The plot shows the approximate coverage for the 15 meter yagi's rotatable side mount.

Unlike the 40 meter Moxon, the 5-element yagi can't be reversed to double the azimuth coverage. That's okay for my situation on 15 meters so I followed the same design as for the first rotatable side mount. Deviations from that design are minor, to accommodate differences on the mounting location and the coverage objective. 

Last fall I picked up a used Ham-IV rotator and controller. It looked clean on the outside and proved to be in good condition on the inside. That's more than enough rotator for the weight and wind area of the 15 meter yagi. A swing gate would require a far heftier rotator to deal with the high torque of an offset load.

Since the weight of the yagi, mast and rotator bears on the lower strut, I used 4" × ¼" steel angle. It was scrap and rusted but perfect for the application. I cut a rectangle of ¼" steel plate with conveniently located holes that lined up with slots in the angle stock. This made a sturdy platform that put the rotator far enough from the tower to allow rotation from about 60° (through north) to 280°, just as I wanted. The slots permit a small adjustment range to align the rotator and mast bushing

The strut is strong enough to support my weight and even jump up and down on it, which I did to test it after installation -- I should point out that I don't weight much so be very careful about trying this yourself! Unlike the aluminum strut that I used on the other rotatable side mount, there is no need for a support cable to keep it from deflecting under load. If it becomes a problem later I can easily add it.

The LR20 guyed tower is popular in Canadian big stations while rare elsewhere. Mechanical details will therefore be of little interest for most readers. Nevertheless, the design and construction process can be applied to other towers. I keep a section of LR20 (10' high, 120 lb) in my workshop as a jig for jobs like this.

The first challenge is that I had to use a different tower girt for this side mount. There are two guy/support girts on each section. Due to the yagi's position the girt for the lower strut has to fit between the guy yokes and section splice bolts. Pictures will help so here are a few.

On the left you can see the two cutouts for the splice bolts. I cut the angle stock with an abrasion wheel on a circular saw. Since it's out of sight high on the tower it doesn't have to be pretty! I regularized the slots as well as I could and removed all sharp edges and points. The strut was descaled and painted.

The strut couldn't be centred on the girt due to the guy yokes. A short length of steel angle stock seats the strut on top of the girt. 3" ×⅜" aluminum angles are used as fore and aft clamps to the girt to keep the strut stable under the stress of the weight of the yagi, rotator and mast on the far end of the strut. The clamps are cut with peculiar angles to fit the insides of the tower legs. 

The rotator plate will be shown in a later picture. It is outboard of the strut to maximize the rotation range. They are joined by ⅝" grade 5 hardware.

The upper strut only has to deal with lateral forces. The 1.9" O.D. 6061-T6 pipe mast runs through a 2-⅜"O.D. schedule 80 pipe section, which is used as a bushing. This is identical to the other rotatable side mount that is currently used for the 40 meter Moxon. I considered a polymer bushing, which I have in stock, but that is more difficult to clamp to the strut without crushing the polymer. I took the easy path rather than fuss with a more elaborate design to accommodate the polymer cylinder. 

The upper strut pivots on the rear bolt to the girt. The outer end is adjustable with a threaded rod that runs through the strut and a bracket bolted to the back girt. While not very visible in these pictures the design is almost identical to the one for the other rotatable side mount (I provided a link to that article above). By swinging the upper strut and sliding the rotator plate on the lower strut slots the mast can be vertically aligned and rotated without binding. 

On the right you can see the boom of the yagi still supported on the original plate that is attached to the tower with pinch clamps. A chain holds the boom to the tower. That becomes the pivot for swinging the boom over to the mast. A pulley and rope support the boom on the rotator side of the tower (centre photo). With the chain and rope lightly supporting the boom, the boom truss and the saddle clamps of the existing fixed side mount are removed. 

With the yagi's weight fully supported by the swing the mast is lifted out of the rotator with one hand and the boom is pushed to the outside of the mast with the other hand. Then the mast is dropped back into the rotator, as seen in the left photo. Although a second pair of hands would have come in handy it wasn't difficult to do.

While not too heavy, it was still awkward to lift and level the yagi to permit attachment of the boom to the mast clamp. The front rope was pulled to raise the boom up to the clamp and tied off to the tower. A second rope was used to lift the boom within the confines of the chain. There is no risk of the yagi escaping during the operation.

Unfortunately the saddle clamps that I selected didn't fit the 3" boom. That was quite a surprise! Since it was time for lunch I left the yagi to bounce in the wind and climbed down. On examining the clamps on the ground I discovered my mistake: I had selected clamps to fit 2-⅞" O.D. pipe. The u-bolts fit but not the saddles.

Since I was out by a small amount I tried to fit the u-bolts through the 3" saddles taken from the old fixed mounting system. To my relief they fit. After lunch I took the mix of u-bolts and saddles up the tower and completed the installation of the yagi to the mast. I was lucky that I didn't need to machine a new mast clamp to accommodate the 3" saddle clamps.

With the yagi attached to the mast it was time to quit for the day. The rain clouds were getting very close. I kept the antenna pointed at Europe and reattached the coax. The clamps were not too tight so the yagi swung on the mast a bit in the high winds that accompanied the rainstorm. It was almost a week until the cold, wind and rain subsided and I could resume work. The remaining tasks included: boom truss, protective rubber bumpers on the tower, coax rotation loop, and alignment with the upper yagi for maximum stacking gain.

Wiring of the rotator was completed last fall when the struts were installed -- this and several other projects were supposed to have been completed before winter struck us early and more severely than expected. The motor phasing capacitor is encased in UV-resistant plastic and a barrier strip matches the 8 wires required for Hy-Gain rotators. 

Wire #1 for ground/common (on the left) is connected to the tower, thus eliminating one of the 8 wires. The phasing capacitor is connected to #4 and #8 to eliminate the need for those wires. Cat5 cable is used for the direction pot wires #3 and #7. The high current wires for the brake (#2) and the motor windings (#5 and #6) are 14/2 electrical cable. 

This is my preferred wiring method for Hy-Gain rotators with long cable runs, well over 100 meters in this case. It gets the job done for the least cost. Copper isn't cheap. Extra cables to support future projects such as this one were thrown into the trench when it was dug during the early days of COVID.

I am still experimenting with the rotation loop, as I will explain shortly. The photos show its current configuration. When the phasing lines from the stack switch were made I included a few feet of slack to ensure adequate length for routing around obstacles and other unforeseen issues. For the lower 15 meter yagi there is approximately 3' (1 m) extra, with most of that coiled at the stack switch.

To make a sufficiently long rotation loop the full length of the LMR400 phasing line was pulled down through the cable ties. Since this is semi-rigid coax the amount of flex during rotation must be limited. The present configuration accomplishes this. It took a few tries to get it tracking properly and ensuring that there was very little stress on the cable.. 

Note: In these and a few other photos you'll see a few seemingly out of place wires and ropes. Those connect and support the two halves of the boom truss during the project. It's no fun having to lean far out from the tower to retrieve a dangling cable and turnbuckle that can easily escape from one's hand. For most of my yagis I tie a short length of rope between the two turnbuckles in case of turnbuckle or cable failure. It's cheap insurance.

The yagi in the previous pictures is pointed at a bearing of approximately 45°. The yagi further down the tower is the lower yagi of the 20 meter stack pointing to Europe at a fixed bearing of about 50°. Due to the offset of the rotator the clockwise stop for the 15 meter yagi is approximately 55°. In the photo immediately above, the yagi is at its counter-clockwise stop, pointing almost west at about 275°. This is the rear of the yagi (facing east) with first director adjacent to the tower. The rubber bumper protects the tower and boom when the operator over-rotates the yagi. The Ham-IV has limited torque and so is easily stopped when it hits a solid obstacle without the risk of damage to the yagi or tower.

Yagi de-tuning with the director so close to the tower is minimal. Coupling interaction is minimum at element centre and maximum when near the element tips. There is in fact more interaction as the yagi is rotated towards north. The measured SWR barely budges. Gain is difficult to measure or model due to the structure of the lattice tower. Modelling that I've done in the past of similar tight coupling is encouraging so I choose not to worry about it.

Of greater concern is stacking gain over the rotation range. Previously, the stacking gain was optimized with the lower yagi fixed towards Europe. Since the rotator is offset from the tower centre, where the upper yagi is centred, the yagis can only be in phase in one direction. In all other directions the feed points are not vertically aligned. For the rotatable side mount the phases are also aligned when both yagi point to Europe. The question is then how much the stacking gain is reduced in other directions due to the phase error.

The top-down diagram demonstrates how the analysis was done. The red dot in the triangular tower's centre shows the position of the upper yagis' mast and rotation centre. The blue dot is the lower yagi's rotation centre. The red dot adjacent to the tower is the 0° phase point that is in alignment (main lobes in phase) with the upper yagi when both yagis point to Europe (northeast).

The circle shows how the phase centre of the lower yagi moves in relation to the tower and upper yagi as the rotator is turned. The phase offset is quite small when the lower yagi points north. Modelling shows that the gain reduction is less than 0.1 db. That's negligible. 

The misalignment becomes quite large when the lower yagi points west. The offset is approximately 5' (150 cm) or roughly 38° at 21 MHz; 150 cm is 0.105λ for the 14.3 meter wavelength; the phase calculation is approximate, not exact.

The elevation plots are overlaid to show the effect. Since the resolution is limited, making it difficult to see small details, I'll mention that main lobe's gain is reduced by 0.5 db. That's not bad. The greater impact is that the nulls between the multiple elevation lobes are shallower, pretty well disappearing at high elevation angles. In a contest that can be helpful since fewer signals will be attenuated when the arrival angle falls into one of those nulls. It is inconvenient to fiddle with the stack switch (BIP, lower and upper by mouse control) for every contact. 

While not shown, the lateral offset of the booms has negligible impact. This is unsurprising since the vertical alignment of the boom (when pointed in the same direction) has little to no impact on the formation of the far field pattern. I took a few minutes to confirm it in the model.

The lower yagi could be slid backward to improve phase alignment to the west. However that would unbalance the wind load, require adjustment of the boom truss, and require greater extension of the coax rotation loop. The last will be difficult. For my style of operating the improvement is not worth the effort. It is rare that I'd benefit from stacking gain to the west. When I do I can live with the 0.5 db deficit. 

Another potential benefit of sliding the boom back is that the first director would be farther from tower when the yagi point west (see above). On the other hand, the front of the yagi (third director) would come closer to the upper guy that is due west, as shown in the adjacent photo. The top guys descend at a sharp angle and this is a large yagi. That interaction could be worse than the one between the first director and tower.

As I finish writing this article there is still some tidying up to do. The most important is the forward boom truss for which the cable isn't long enough to reach the mast. Pieces of the turnbuckle unscrewed and fell down over the winter months and I haven't found them all. 

I am also contemplating replacing the aluminum mast with steel. While not serious, it abrades a little in the rotator mast clamp and bushing. I'll check it again before winter and decide whether to replace it.

Other than these minor items the rotatable side mount is done and I've already tested it to Asia on air. The results are encouraging. As with any combination of antennas like this, especially so they're so high relative to wavelength, there are times when the lower yagi is superior. The reason is that with many elevation lobes there is an increased risk of a signal's arrival angle falling into a pattern null. The more expansive stack arrangement gives me greater ability to deal with those signals.