IARU & WRTC-2026

I don't like summer contests. Focussing on the radios is difficult when the weather is so nice. Winter is more conducive to spending long hours in the shack. The past few years I hosted guest ops for the IARU contest which left me free to do other things. The only real sacrifice is not being able to cover possible openings on 6 meters while the station is occupied.

My station is not in great shape at the moment. In the week leading up to the contest several antennas were disconnected in preparation for repairs. The work was delayed due to unusually hot weather. I got no further than replacing the rotator on the 20-15 tower. Strenuous work in sunny 30° C weather is not enjoyable and can be unsafe. Black flies, mosquitoes and ticks also plague outdoor work.

Rather than offer a deficient station to a guest op I decided to operate the contest myself. The day before the contest I climbed the tower to temporarily reconnect transmission lines where I could. That still left antennas offline or not at their best. A couple of rotators couldn't be used due to interference with work rigging. 

As usual, 160 meters was not really usable this time of year. There are no radials on the big antenna because it is the growing season for the hay crop. The Beverages are weather damaged, as often happens over the summer. Since they are in heavily overgrown bush, I was not even tempted to dive into the "jungle" and contend with ticks and other risks. I simply didn't bother with 160 during the contest. 

Since I didn't expect to be very competitive I had a very relaxed attitude going into the contest. My 2BSIQ skills are modest and I don't practice outside of contests. Also, I operate HF very little during the summer. My log shows that I made fewer than 10 contacts in June! My time on the air this time of year is almost exclusively 6 meters, which is ripe for long haul DX during the sporadic E season.

Preparation for the contest only required reconfiguring the station for SO2R and testing the amps. I opened the windows to keep the shack cool with two amplifiers running. I have air conditioning but I prefer to avoid it except on the hottest days. My entry category was SOAB HP CW; that is, no assistance and no SSB -- contesting in its raw essentials.

WRTC is a contest within a contest which, while important to the 50 teams competing in England, was of little consequence to me. They were just stations to be worked. That doesn't mean I was uninterested in WRTC. I was very interested in how my friends (including a returning gold medal winner) would do. I also had a friend participating as a referee. 

My contest

SOAB HP CW attracts many of the world's best contesters. With many of them in England for WRTC the list of competitors is smaller. That won't make me a winner but it can push me higher in the results. The following is a snapshot from 3830 two days after the contest that may or may not be complete. As always, the following are raw claimed scores and the ordering will likely change after log checking.

I would never rank so high in a non-WRTC year. Perhaps I could have climbed a position or two had I taken the contest more seriously. Certainly the station, even with its current deficiencies, is capable of more. My relaxed attitude is mostly to blame, not my skill. For example, I made no contacts on 160 meters. I checked a few times, heard no stations and didn't bother making a few CQ's before leaving. Just a few contacts, almost all multipliers, with my diminished antennas would have raised my score.

Talking it over with Vlad VE3JM after the contest there were some interesting insights. Some of those are included in this article. Our perspectives are different since he was a serious competitor and his 2BSIQ ability is far superior to mine. He and the other top competitors participated in the online scoreboard and enjoyed chasing each other when one or the other fell behind. 

I took no sleep break in this contest. It was hardly necessary since it started early in the morning our time (8 AM) and it's only 24 hours long. I wasn't active full time, opting to take breaks at regular mealtimes and to take in the fresh air. When the pile ups because fierce I abandonned 2BSIQ to run stations faster on just one radio. None of this contributes to a competitive score!

40 meter stayed open well after European sunrise, late in our nighttime. At the same time 20 meters was booming into Europe. This is not unusual, although the 20 meter opening can't be counted on when the solar flux hovers around 100. The solar maximum is long past. Soon enough 20 meters faded and the rate plummeted. It continued that way right up to end of contest. 15 meters didn't generate many workable signals in the morning despite the sunlight. A minor geomagnetic disturbance didn't help.

After a quick breakfast I grabbed a few hours of sleep then went about my day. The one thing I did before getting out of the chair was to submit my log. WRTC requested rapid log submission from all participants to assist with log checking the WRTC competitors. I had taken a few notes during the contest to correct a few log entries but, as often happens, they were too cryptic to deal with. I sent in the log as is. It was not as if I was going to win. 

Participation notes

When no band is open to Europe we notice it. This is especially true on CW. Without Europe the rest of the world seems further away. But there so many stations to work within North America. At least there used to be. That is no longer true.

There was almost nothing to work on the low bands overnight. When I'd switch bands I'd get callers for maybe 5 minutes. Then I'd hunt for stations, which would occupy me for several more minutes. After that I could CQ for a very low rate or switch bands. Yes, I had SO2R but that didn't help. There was next to nothing to work on 40 and 80, and 160 was worse.

While this was going on, the Europeans continued their high rates. Their QSO counts on the low bands dwarfed those of us in Canada and the US. Contest activity is much higher in Europe. They could also work east Asia on the high bands, which was almost out of reach to us this time of the year and sunspot cycle. Vlad, who was connected to the online scoreboard watched the Europeans run away with the contest. I didn't see that but noted to myself that I probably worked more Australians on 40 than Canadians on 80.

The situation is less dire on phone. Yet even there the decline is apparent. We see it in other contests as well. ARRL Sweepstakes rings the alarm bells since in a contest where you can work stations only once regardless of band. Our declining numbers have an enormous impact. The older hams are dying and few of the newer hams are learning CW or paying much attention to HF beyond POTA. Yet there are more hams than ever before.

This is the story that won't go away. All I can do is point the fixed antennas of my stacked yagis northeast -- that's a joke, or maybe not. I only mention the low participation because of its impact on our reduced potential in the IARU contest. I have no fantastical solutions to offer.

Another disappointment was the absence of a Canadian headquarters station. No one stepped up to put a RAC station on air during the contest. What seemed of more interest to many was trying to work all of the WRTC (MB) stations. That's more akin to playing bingo, not contesting. I believe we should aim higher.

WRTC

It was exciting to learn that fellow CCO (Contest Club Ontario) member Yuri VE3DZ made it two in a row. Our congratulations to him and Yaroslav UW7LL. In a contest there is always the element of chance. When you do it twice there is little doubt that they are true champions. Another team I know well -- Todd VE5MX and John VE3EJ -- also placed well. John is a previous gold medal winner.

This picture of the winners was taken by my friend Chris VO2AC. He participated in WRTC as a referee. His assigned team was Champ E21EIC and Dale BA4TB. When he returns home it'll be interesting to hear of his experiences.

The WRTC stations seemed of equal capability from I could hear. Their 80 and 40 meter signals were very similar strength. That comparison can't be done on the high bands since they had rotatable yagis. Often they fought for a place in the bottom 10 kHz of the band which, despite the majority of contesters doing point-and-click hunting, pays dividends. I didn't bother trying to elbow in since I was not so serious; any open spot on the waterfall suited.

We like to think that the WRTC teams are the best of the best. That's not entirely true. Many of the best contesters are not interested in WRTC. From what I heard they all handled the pile ups well, picking calls correctly. It must also be said that I and others observed instances of competitors attempting to steal run frequencies and other common infractions. Thankfully these incidents were few.

So what does make you a winner? The selection criteria are not really well aligned with the format of WRTC. For example, the world's best 2BSIQ operators operating from the world's best stations win contests. Except there is no 2BSIQ in WRTC and it's a multi-op (M/2) competition, not single op, using small stations. Successful tactics and strategies are necessarily different in WRTC.

One thing I noted that may or may not be relevant is that the winning team appears to have won on multipliers, not contacts. I thing I've always noticed about Yuri is that he is very smooth at asking needed mults to move to another band. He does it even while operating 2BSIQ -- I've listened to him operate. Perhaps that gave them an edge. But my guesses are often wrong! What do I know.

Back to work

With the contest out of the way it is time to return to station work. It's a little awkward this time of year since I have only a little room at the base of the big towers where I mow the hay. I won't ask anyone to walk into the hay with a rope since the tick risk is high. So I either wait until after the harvest or rig the antennas to avoid the need for long ropes. I do a little of both.

August is going to be busy for me and potential helpers so I'd like to get a few of the repair jobs done now. You can count on future articles that will describe the work. Now I have to get back to 6 meters to milk what's left of this year's sporadic E season.

Yaesu G2800 Replaces a Prop Pitch Motor

It is very difficult to keep water out of the gearbox of a prop pitch motor that is mounted upside down. I have one of those and one that is mounted right side up with a chain drive. The latter has never given me any trouble, and others I've spoken with a similar setup have also had good success. 

Most prop pitch motors used as rotator are mounted upside down including those by K7NV (SK). There are ways to seal the opening to the gearbox against water incursion but none seem foolproof. There are numerous channels and seals that serve its design in aircraft but are trouble when used as a rotator .The hydraulic pressure of wind driven rain and ice damming in winter causes water to overcome the barriers I made and pool around the crown bearing where it eventually migrates to the interior of the gearbox.

I gave it a shot with the materials that I could work with in my home workshop and my various attempts weren't good enough. For the second time the gearbox for the prop pitch motor turning the upper yagis of my 15 and 20 meter 5-element stacks froze this spring. 

After taking it down and doing an inspection I found extensive water fouling of the reduction gears and two stuck bearings. I am retiring this prop pitch motor. The pieces, along with a spare motor, are now boxed up. They can be used as spare parts should I need to service my one remaining prop pitch rotator or those of my friends. There seem to be no commercial service options since the passing of Kurt K7NV. I receive many queries due to this blog and there is little that I can do other than offer advice.

I don't want to deal with the issue again so I've been preparing for this day. Last winter I acquired a used Yaesu G2800 in excellent condition and a Green Heron RT21 controller. The stack is within the specifications for what the rotator can handle, though not by a lot. However, there is no weight bearing on the rotator since I have an industrial sealed bearing under the mast to do that. This arrangement eases service of the mast and rotators. In any case, prop pitch motors are not designed for substantial axial loads.

I locked the mast where it was which left the yagis pointing at 15°. That's not an ideal direction but I have lots of antennas and there were no important contests or DXpeditions of great interest to me in late spring and early summer. It was simply going to stay like that until I had time to devote to the rotator system. Tower work is not ideal this time of year due to the intense heat and clouds of insects in the hay field where the towers are located. I did most of the work described in this article at temperatures around 30° C. Autumn is when I prefer to do tower work, but you don't always have that option.

The central hole in the support plate for the prop pitch motor was too wide for the bolt pattern of the G2800. The plate was therefore removed and a new one made from ⅛" galvanized steel found in my scrap pile. It already had many holes in it though none where I needed them! The sheet is barely wide enough to reach the mounting holes on the tower girt. I've discussed centering of bearings and rotators on tower plates in several other articles so I'll move on.

I used the removed plate as a template and then used the pattern of the mounting bolt holes to locate plate centre. Positions for the 4 bolt holes were calculated from plate centre then checked by mounting the rotator. Never assume you did it right; it is surprisingly easy to make mistakes. Validate before and after punching the holes. Last year I had to do the same for a friend's Yaesu rotator with little time and few tools. It didn't go so well so one of the holes had to be extended. Take the time to do it right since alignment is critical in many installations.

Centering of the rotator is critical in my case since the rotator barely fits between the girt and the mast coupler hanging below the bearing plate above (see below). An error of even 1 or 2 mm can stress the rotator and potentially bind due to flexing of the plate and coupler. The alternative was to place the rotator on the next lower girt. The mast is already very long and I preferred to avoid adding 40" (100 cm) to it. Too long a mast amplifies torque induced oscillations that can stress the antennas, mast and rotator.

The picture below shows the tight fit. There are just a few centimeters between the top of the mast clamp and the mast coupler. I made the coupler out of 1.9" OD aluminum (6061-T6) schedule 80 pipe. The same ⅜" grade 8 bolt that pierced the coupler for the prop pitch motor is reused. That is the only hole in the pipe. When I came to tighten the jam nut on the bolt it sheared. Grade 8 bolts are hard but can be brittle, especially at the threads. The bolt was carefully selected so that the load bearing surfaces (the 4 points where it contacts the pipe walls) are unthreaded.

Grade 5 bolts, although tougher, are weaker in shear. I'll have to replace the bolt or secure the nut another way (e.g. hose clamp). Lock washers are ineffective on round surfaces.

Looks simple? It took me 3 tries, each involving a tower climb. On the first try I made a simple recording error and the coupler was precisely 1" too long. On the second try I failed to account for the "seat" on the rotator mast clamp. I assumed that the mast rested on the rotator body. Oops!

Even seemingly routine tasks can become expensive when a tower is involved. I can't machine metal 130' up in the air. It wasn't as bad as it might have been since I had lots of other work to do on the tower so none of the climbs were solely to correct my mistakes.

I did not use the 4 centering bolts on the mast coupler. These were added several years ago when I found there was too much slop in the fit of the prop pitch motor coupler -- it was 1.66" steel pipe welded to the crown gear. That caused rapid wear and stress on the coupler through-bolt, which contributed to its shearing. At the time that was a 5/16" grade 5 bolt, since upgraded to ⅜" grade 8 as described earlier.

As you can see, the fit is pretty good and the coupler well centred. The centering bolts are still there, locked but retracted, just in case I decide to use them again.

The Yaesu mast clamp can handle a wider range of mast diameters than those of many other rotators. That comes at the expense of a multi-step alignment procedure. It isn't too complicated but must be done properly to avoid trouble. First, the two clam shells of the clamp are bolted together to grip the mast. When done properly, the width of the slot between both sides of the clamp should be equal on both sides and along their full lengths. It is well worth the time to fuss over it to ensure stress equalization and mast centering. 

The bolts have only one correct orientation. Note the captivating tangs to fit the bolt heads -- that's how you know you've got it right. It is also handy since it takes just one 13 mm wrench to tighten the 6 bolts. The next step is to tighten the 4 bolts (with the same 13 mm wrench) that hold the mast clamp to the rotator body. When the mast is properly centred the positions of the bolts within their slots (not shown) will be identical for all 4 of them. If they aren't, something is amiss with the centering and you must recheck your work. Luckily mine were properly aligned so I was effectively done.

One point worth noting is that I left the 6 bolts holding the plate to the tower girt loose during the alignment process. That way the plate can shift within the small amount of play in the holes. Only after the mast alignment procedure was complete to my satisfaction were the plate mounting bolts tightened.

One part I did not use was the mast locking pin. I avoid those since there is a risk of damaging the rotator when a high wind applies a momentary high torque to the mast. Unless you are very confident in your calculations avoid these devices. It is preferable to occasionally have to correct a slipped mast than to deal with a broken rotator. Although the clam shell mast clamp on the G2800 appears to have a good grip, I'll have to wait and see how it deals with the wind load of two very large HF yagis. I am already close to the 'K' rating documented in the rotator manual.

I had previously completed the wiring of the rotator and tested it from the shack for full rotation, just sitting on the tower plate without the mast clamp. The wiring was interesting. Although the rotator came with almost 100' of cable it was not usable in my station. It's far too short -- the run is >300' or 100 meters -- and would have to be buried. Instead I reused the motor wires for the prop pitch motor and used spare wires on existing control cables.

I have a history of innovative wiring of Hy-Gain rotators and the same can be done for Yaesu. Ground is easy: tie it to the tower/antenna common ground, which is tied to electrical ground. Thus freed, the 3 wires of the 10/2 cable for the prop pitch motor provide the 3 wires to the motor: CW, CCW and motor common. For the two direction pot wires, a Cat5 cable was run from the G2800 to the one for the lower 15 meter yagi, patched in to a spare pair, patched into a spare pair on a buried Cat5 cable, then patched again at the far end to a spare Cat5 pair running into the house. Other than a some tedious cable tracing (I keep detailed cable wiring records) it was perfectly straight forward.

Before attaching the rotator to the mast, I re-calibrated the rotator controller to account for the resistance of the long cable. After confirming that all was working as it should it was time to test the rotator.

My initial plan was to be on the tower while a friend operated the rotator from the shack. I wanted to watch the rotation to check for any stress points or other problems. However I had to move quickly since I wanted the stacks ready for the IARU this weekend and it wouldn't be fair to ask someone to drive to my remote QTH on an hour's notice. I can do that test after the contest.

Suffice to say that there were no issues. I turned the large arrays at the rotator's slowest speed setting and then increased it to its midway point. For such large antennas it is unwise to turn them faster due to their high momentum when you remove power. The 90° over-rotation feature of the G2800 also must be avoided since the length of the coax rotation loops aren't designed to accommodate 450° of rotation.

I must now contemplate another rotator controller on the operating desk. The new addition makes 5: 3× Hy-Gain rotators, the G2800 and my home brew prop pitch motor controller. I now use the last for only the motor on the other tower -- 3-element 40 meter yagi and upper 5-element 10 meter yagi -- however, the mast operated direction pot on the 20-10 stacks still works but is redundant. I have no good reason to remove it. When they disagree I guess I'll have to look out the window to know which one is right.

I may replace my home brew controller with the Green Heron controller since it is more robust and has more features. That wasn't possible when my controller needed to support two prop pitch motors. I've heard rumours that Yaesu controllers are failure prone so I intended to keep the RT21 in reserve. Certainly they are electrically and mechanically complex. Time will tell. 

A more serious issue is the proliferation of controllers on the operating desk. I would like to migrate to software control using PSTrotator, which I've used at other stations and it seems to work well. Most operators like physical controllers but they have to reach for them and pick the right one during hectic multi-op contests. Mistakes happen! The migration that won't happen quickly. It's a project to mull over during the cold winter months.

Incompatible and Missing Connectors

When you buy a new, expensive HF transceiver you will invariably find that they include a small plastic bag containing a variety of connectors. This is helpful since the back panels can have a variety of connectors for peripheral equipment and devices. These include antennas, keys, audio, amplifiers, transverters, automatic tuners, etc. 

Some of these connectors are quite common (3.5 mm stereo) while others can be uncommon (various DIN connectors). The ones that aren't included can almost always be found commercially so that you can make interconnect cables for your unique requirements. There is also a thriving business in providing ready-made cables for connecting various combinations of equipment. The latter are quite expensive -- far more than the BoM (bill of materials) -- catering to those who willingly pay for the convenience for a niche product.

What I find more interesting than what's in those connector bags is what isn't included.

Modern rigs, especially the more expensive ones, have lots of features. Lots of features means lots of connectors. Eventually it is likely that most will become incorporated into data lines, wired or wireless. We're not there yet so we continue to deal with a multitude of connectors.

The above diagram is from the FTdx5000 manual. It shows the cables needed to connect the transceiver to Yaesu's VL-1000 amplifier. Notice the annotations: the interconnect cables are included with the amplifier, not the transceiver. While that isn't unreasonable, I am not amused that they don't include the transceiver connectors in those little plastic bags.

There are features exposed via those connectors that are more useful than connecting a proprietary amplifier. Yet all the major manufacturers fail to supply them. They are all standard but inconvenient to purchase in quantities of one. It's as if they believe that customers will pay $8,000 for an amplifier to avoid the inconvenience of purchasing a few $2 connectors.

The worst of these are the DIN connectors. These are not connector types but a standard that encompasses a wide range of connectors. Knowing the number of pins isn't sufficient. 

Connectors with the same number of pins can have a different placement and diameter of pins and the size of the barrel may be different. I made this mistake more than once. Cheap connectors may not fit at all despite the correct labelling. Coax connectors have also been known to disappoint. I toss the rejects into a drawer and forgot about them while I try again.

Yet there are serendipitous discoveries that are delightful. Look at that 5-pin connector. It turns out that the 3, 5 and 7 pin male connectors of this size fit the same and higher pin-count female connectors. The receptacle on the rear of the Icom 7600 has 7 pins. The 5-pin male connector fits perfectly Of course you shouldn't try to fit a 7-pin male connectors into a 5-pin female.

I did this because I had a discarded and otherwise useless 5-pin connector and the signals I wanted -- ground and Icom voltage-level band data -- to interconnect with an amplifier for automatic band switching were found on those pins. It works great. You just never know until you try.

In the second case, I cheated and found a wire size that snugly fits the adjacent DIN receptacle to connect a foot switch. The downside is that there is no key to tell which pin it fits into. I make a sticky note as a reminder or look it up in the manual. At the time I did it there was a contest coming up and there was no time to order the proper connector.

It is also amusing (if you think things like this are funny) that the 8-pin Foster connectors for the microphone is used on both Icom and Yaesu transceiver front panels are not compatible. I wonder if they did it on purpose, out of ignorance or simply couldn't be bothered to align the pin assignments. They could hve done it for the mic connections while using the remaining pins for proprietary features (scanning, etc.) that almost nobody uses. Of course their own branded desk mics -- not the handheld mics included with the rig -- are sold at a steep markup. 

Those mics are of no use to me; I use a headset and foot switch. I make adaptors to convert the 8-pin mic connector to 3.5 mm stereo for an electret mic element. Over the years I've collected a pile of discarded microphones, some of which I assembled for the above photo. They're almost impossible to sell at local flea markets. The only uses I have for them are testing and for non-ham guests. They are easy to understand and use by curious visitors.

I am not amused by the tactics of the equipment manufacturers, whether it is by design or disinterest. This has been going on for so long that I doubt it will ever change. Even when -- and it is very likely to happen, eventually -- most of the connectors are replaced by TCP networking, wired or wireless, the protocols are certain to be proprietary and incompatible. For example, DPD for low distortion SSB on select high-end Icom transceivers uses a proprietary protocol to include the PW2 amplifier in the feedback loop. No other amplifiers are permitted.

This tactic will convince few buyers, yet Icom and the other manufacturers do it anyway. It's all of a type with the non-inclusion of connectors and incompatible connectors. I confidently predict this marketing tactic (hardly a strategy) will continue into the indefinite future. 

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.