Case of the Missing HF Spice

One consequence of the pandemic has been a dearth of DXpeditions. You might therefore think that the DXpeditions or other moderately rare DX stations would receive more attention than usual. This is what economists call supply and demand: there is less supply so the demand should be high because we are spending far more time at home. That is, we should be willing to pay a high "price" for the rare DX.

That hasn't happened. When these stations did appear the pile ups were not deep. For many of them I found it took just one call to get through. As regular readers know I do have a few big antennas, and that does make it easier. Yet there is more to the story because there is less competition in the pile ups. Most of the time I was successfully working the pile ups without turning on the amplifier. I always try that first since it's a bother to turn on and warm up the tubes and the power boost hasn't been necessary except on 160 meters.

Which brings us to the second consequence of the epidemic: apathy. It has been widely reported that despite the additional time we are spending at home many of us are not taking advantage. For hams that means spending less time on the air or on radio projects. There are notable exceptions, like the increased activity in contests. That is good for me since I'm a contester. But these are exceptions and not the rule.

All communications services are subject to the network effect: service usage strongly outpaces the growth of service users. As deployment proceeds, usage growth is geometric. Think of the telephone in its early years. Imagine you're the only person with a phone in town. You have no one to call so you don't use it very much. As more phones are deployed you have more people to call, so you do, and so does everybody else. 

Amateur radio is the same. When many hams exit their shacks, many more follow. The bands sound dead and we lose interest. Bland food isn't tasty; apathy is contagious. The network effect also works in reverse.

The network effect applies to other aspects of the hobby. You don't like digital? What do you do when you have few left to work on other modes? This happened to me on 6 meters with FT8. The network effect is in play with digital, no matter your feelings or mine. I'm even beginning to like it.

No one to talk to with the same interests you have? You move to where the activity is or you lose interest. You might even leave the hobby. As activity for your favourite mode declines the overall decline accelerates so that total silence seems to happen overnight. The transition to FT8 on 6 meters was measure in months, not years. You can call CQ using AM but do not expect a reply except on select frequencies where the remaining aficionados congregate.

Another reason activity declines is due to the same old, same old syndrome. For many, interest is spurred by novelty. DXpeditions spur our interest. The novelty of digital modes is the same. It's akin to spicing our bland foods.

Non-DXers may grow curious and increase their activity when they hear the excitement on the bands over a rare one. Some will jump into the pile ups despite their indifference. The same happens in contests, with non-contesters coming on the band, hearing the activity and jumping in to make a few contacts. Do you hear some peculiar warbles on the band? You download the software and have a look to see what the excitement it's all about.

Excitement breeds excitement. Imagine going for a walk in the quiet of night. You unexpectedly run into a street party with music and dancing and happy people. You stop to watch. Someone grabs your hand and you think, why not, and soon you're dancing, too.

Getting back to DX, maybe it's just my imagination that I am beginning to see more excitement on the bands. The DXpeditions that make an appearance are garnering bigger and more enthusiastic pile ups than they have for many months. 

Perhaps it the rollout of the vaccines that promise an end to the pandemic. People are perking up everywhere, and not only on the ham bands, so it may be more than my overactive imagination. I've seen the renewed excitement with the A25RU operation and others.

Sunspots, vaccines, contests, DXpeditions and more. HF is once again tasting spicy.

Reflections: The Downside of Height

As my antennas get higher I run into novel difficulties. In one sense it's a nice problem to have considering that few hams have antennas that are large or high. Nevertheless it is a problem. In this article I'll review the affect of height on horizontally polarized antennas (primarily yagis) before discussing my own particular challenges and mitigation strategies.

Even for those without this problem the discussion may be of interest and educational. Some of the material is elementary. Antenna height has been covered numerous times in this blog (and countless times elsewhere) and I will reference earlier articles for details that are only touched on lightly in this one.

The antenna does not determine the path

Higher antennas are not always better. More precisely, for an antenna that is already reasonably high, higher is not always better. This is not due to diminishing returns so much as the potential mismatch between the antenna's pattern and what the ionosphere requires for communication.

Put another way, an effective antenna is one in which its most effective direction is the one that nature demands for the intended communication. Nature chooses the direction. Your job is to design and install an antenna that is effective for that direction. The antenna does not determine the path.

Direction is 3-dimensional so we must consider both azimuth and elevation. Good presentations of antenna patterns show both. Let's dispense with azimuth quickly by noting that the correct azimuth is the great circle route (short or long path); that is, except when it isn't! Skew path is not at all rare on the lowest HF bands and on the band closest to the MUF. Smart operators turn their antennas to find the optimum azimuth during difficult conditions.

With that out of the way let's turn to elevation angle. Good DX paths are more common at low elevation angles. There are exceptions; there are always exceptions. An effective vertically polarized antenna with its far field reflections from a high conductivity ground (e.g. seawater) can have an impressively low elevation angle for its main lobe. Most vertical antennas don't do nearly so well. 

Horizontal antennas usually do better over typical ground (medium to poor) when they are high enough. In context, high is with respect to wavelength. On 40 meters and down the height to put the maximum radiation at the required low elevation angle for most DX paths is difficult to impossible for most hams. Hence the prevalence of verticals on 80 and 160 meters. For DXing on these low bands, a moderately efficient vertical typically outperforms a horizontally polarized antenna with the same apex height.

When great height is possible there are dangers lurking. Higher isn't necessarily better. This is a lesson I am learning every day with my complement of low, high and higher antennas.

Modelling height

Software makes it easy to inspect the elevation patterns of antennas at various heights. Consider the following set of patterns for a 5-element yagi at heights from ½λ to 4λ over medium EZNEC ground. Although I am illustrating the effect of height with a 20 meter yagi the pattern is scalable to other bands. 

The elevation pattern scales with wavelength. If you get dizzy thinking about an 84 meter height for a 4λ on 20 meters, you can instead imagine a 2 meter yagi that is merely 8 meters high.

This is a busy plot that may be difficult to read. To help out I'll list a few key points:

• Starting at 1λ there is more than one forward lobe. Their quantity increases as height increases.
• There are deep nulls between those lobes, and that will cause difficulties on the air.
• Maximum gain increases with height due to the concentration of energy at lower angles.
• Low angle radiation increases quite a lot at greater heights. For example, at 5° the gain for the yagi up 2λ is ~6 db better than one up ½λ. Diminishing returns are rapid at greater height.
• By choosing heights that are an integral multiple of ½λ the radiation directly upward is cancelled. I did this deliberately for the plot and it is worth keeping in mind when planning your next tower.

As a general rule, the higher you go the greater the number of elevation lobes and nulls. These can be aggravating since when the signal comes in at an angle where there is a null the antenna will not serve you well. Unfortunately there will always be signals that strike those nulls. It is worth addressing for the contest enthusiast, but also for daily operating enjoyment and DXing.

Many VHF operators may be unaware of the problem since DX paths tend to be at low elevation angles. That is often not the case for sporadic E propagation, as one example. An elevation rotator for satellites and EME can deal with the problem at high elevation angles, where "high" means an elevation angle greater than the half-beam width of the main lobe in free space (see below). 

How those lobes and nulls form

The pattern of any antenna doesn't start at the horizon. All radiate downward. A free space elevation plot makes this evident. At right is one for the yagi discussed above.

The elevation patterns above and below the horizontal axis (0° elevation) are mirror images. When placed over ground the downward radiation is absorbed (dissipated) or reflected upward. 

The half of the radiation that reflects from the ground adds to the direct (skyward) radiation to form an interference pattern by superposition. That interference pattern is the series of lobes (reinforcement) and nulls (cancellation). 

Perfect addition and subtraction requires the amplitude of the ground reflection to be equal to the direct radiation. This is approximately true for horizontal polarization even for poor ground quality. 

When the fields add the radiation in the lobe is boosted by 6 db. Where the phase difference is 180° the null is exactly zero. Of course it's never exactly zero, and over real ground will rarely be deeper than -20 db below the peaks of the adjacent lobes.

At right is the broadside elevation pattern of a simple dipole 4λ above ground. Perfect and poor ground are compared. The effects of ground are easier to see with a dipole than with a yagi.

The first thing to notice is that over poor ground the nulls are not so deep and the lobes not so large. Poor ground absorbs more at high incidence angles so the reflections are weaker. In addition to that, the phase shift will not be 180°. Perfect ground does not have these deficits. The effect of poor ground is modest with respect to filling the nulls, and is negligible at low angles that are of interest to DXers. At low angles even poor ground reflects well.

The second is that the angle between adjacent lobes and nulls is smaller at low angles than at high angles. This is due to the more rapid change in the path length of reflections as the elevation angle decreases. This puts more of those deep nulls at low elevation angles where we don't want them. The higher the antenna the worse the problem.

This review should have been elementary to most hams. It is nevertheless worth recapping the basics before going further.

Terrain

The previous discussion assumes flat terrain, and that is not the case for many. Terrain plays an important role in determining the elevation angles of lobes and nulls, and can be the dominant factor where there are major slopes, hills and other large geographic features.

To solve the terrain problem the usual antenna modelling systems are not helpful. Modelling terrain requires real topographic data and a ray tracing tool like HFTA. I have never used HFTA for my station since the land here is quite flat, with gentle slopes and undulations for many kilometers in all directions. Urban hams also have little to gain from HFTA since although the land may be flat all those buildings and metal infrastructure are near impossible to model.

For those with topography that is not flat and open it is advisable to use HFTA to investigate candidate antenna heights and to calculate the elevation angles of the lobes and nulls. In some cases a low tower will be sufficient to achieve both a low elevation angle and few nulls. For others no tower is high enough. 

One recent correspondent who is working on a 40 meter wire yagi put up the first inverted vee element. It is outperforming his vertical on his most important DX path. The reason is that the land slopes downward in that direction. His experience is typical. It is possible to get an idea of how an antenna in his location will perform in NEC2 by tilting the antenna upward by the same angle as the downward slope (or vice versa for an upward slope) and subtracting that angle from the elevation plot.

Beyond this rudimentary advice I have little to say to those with complex terrain. Use HFTA to find what will work best in your unique circumstance.

Mitigation

You cannot fill an elevation pattern null by aiming above the horizon on any HF band. The ground reflection remains and dominates the far field pattern. For high gain stacked arrays for 2 meters and above tilting can work very well. For these antennas the elevation beam width is narrow and the ground-directed radiation falls off rapidly when the antenna is tilted up. In essence, the ground disappears and the antenna performs as if in free space.

An elevation rotator is routinely used for satellite and EME communication. For low elevation angle terrestrial paths or for low elevation EME and satellite work the ground is as much a factor as it is at HF. At the lowest elevation angles the ground reflections will dominate and cause elevation pattern nulls. Too often those nulls are at inconvenient angles. The only good options are to switch to vertical or circular polarization or to wait a minute or two for the moon or satellite to move.

To fill elevation pattern nulls there are a few common strategies:

• More than one antenna: Having one horizontal and one vertical antenna is perhaps the easiest way to deal with nulls. Switch between antennas and see which is better. The comparison must be longer than a few seconds because of signal fading and Faraday rotation that continuously changes signal polarization.
  
• Stacking: Yagis at different heights are fed in phase, out of phase (BOP) or separately to select the one that works best.
  

Did you notice that the two bullets are related? A stack has more than one antenna, and it is important that they can be individually selected. This is typical for HF stacks since it is so useful for optimizing elevation angle to the path and for avoiding nulls. Yagis in a stack for 2 meters and up are rarely configured to allow selection of one or a subset of them since it isn't as beneficial as at HF.

By feeding the yagis out of phase the nulls and lobes largely reverse. The elevation plot compares BIP and BOP for my stack of 5-element 20 meter yagis. The reversal isn't perfect but it is close. Gain in the BOP lobes provided little if any advantage over selecting the lower yagi alone. BOP was enough additional work for my home brew stack switches that I decided it wasn't worth the bother. Many commercial stack switches have the BOP feature, at a price.

For maximum versatility of elevation angle it is necessary to have at least two antennas, either in a stack or at different heights. One antenna, be it high or low, is a competitive disadvantage for contests and for DXing. I am sure that readers struggling to raise just one antenna per band, or even just one multi-band antenna, are feeling less than sympathetic about my plight! Nevertheless this is what I must deal with to achieve my operating objectives.

By the end of this year I'll have stacks or multiple antennas for 40, 20, 15 and 10 meters. For 80 meters I may reinstall my trusty inverted vee to have a high angle antenna to complement the vertical yagi. It would be useful on some paths, especially when I'm not running low power or QRP. With a kilowatt I can almost always work the nearby stations with the less effective low elevation angle of the vertical array.

On 6 meters I have a problem with just the one yagi. It is up 4λ and has the elevation pattern shown in the plot at the top of this article. Sporadic E and aurora often have optimum paths well above the horizon. That said, the antenna works well for the longest DX paths with that very low main lobe. There are times when friends nearby with lower yagis do better, which is strong evidence that the elevation pattern nulls are putting me at a disadvantage some of the time.

I would like to have at least 2 yagis in a stack for 6 meters. Unfortunately that's not a project for this year. It isn't even obvious where I could put it; the towers are rapidly filling with HF yagis. I need the gain and I need to fill those nulls to aggressively increase my country count on the magic band. I'll come up with a plan next winter in the hope of building a stack in 2022.

Now let's talk about verticals. These include vertical dipoles, monopoles with a radial system and vertically fed loops. When ground mounted or close to ground they have no nulls between 0° and at least 45°. Like horizontal antennas, the main lobe will split and form a null at greater heights. Although there is no critically located null for most verticals there are other difficulties.

First, verticals for the high HF bands are short, and in almost all locations will have to radiate through buildings, utilities, foliage and other common obstructions. This impairs both efficiency and effectiveness. Even with a good radial system a hex beam mounted on the roof of a house will outperform a vertical monopole or dipole, though usually not a full wave loop in its favoured directions. Ground reflections are not as reliably strong as they are for horizontal polarization, and that can cost a few decibels.

The elevation plot at right compares a ¼λ vertical with 8 full-size radials over medium ground versus a hex beam up ½λ. This is an estimate of what to expect from a ¼λ vertical in many urban and suburban situations. I believe it is fair to compare the vertical to a small yagi with gain (directivity) since the installation difficulties are of similar order. Only half the forward lobe difference is due to the yagi's gain. The rest is due to near field and far field ground loss.

On the low bands it is rare for a horizontal antenna to be very high, and that is why verticals are popular for 40, 80 and 160 meters. Unfortunately the vertical is not a good way to fill nulls on those bands since the horizontal antennas are so low they typically have none. Go back and look at the first plot in this article for yagis up ½λ and 1λ. Verticals are used on the low bands since, as inefficient as they often are, they are superior for low elevation angles over horizontal antenna at practical heights.

No magic

If you were expecting me to propose one highly effective antenna with the magical property of having few or no elevation nulls, I am sorry to disappoint. There are no easy solutions. It is no surprise that big gun stations have lots of antennas on each band, since that is the only reliable way to deal with the vagaries of propagation.

The smart operator at a large station will periodically try different antennas and stack combinations. Propagation changes throughout the day and night, and what worked best an hour ago may not be what works best now.

A Contest of My Own

This past weekend was the annual running of the ARRL DX SSB contest. As contests go this is no longer one of my favourites. Also, I don't really enjoy phone contests as much as I once did. It is a DX contest, which I find attractive, but the experience is different for most outside of the US and Canada. For them it's more of a QSO party in which everyone within a limited area work those outside and vice versa. For example, if you're in far away Australia or south Asia the possibilities in this contest are terribly limited. Few bother, and I don't blame them. I would do the same in their position.

I had concerns aside from being busy and wanting to limit my operating time, while still make a good showing. Two of my headsets failed immediately before the contest. That was a difficulty I overcame with an uncomfortable workaround. Another problem was that I wanted to enter a category that the contest sponsor does not support. 

For those reasons and since I had no illusions about winning anything I decided to do it my way. The alternatives -- conforming my operating to categories set by the sponsor, or to sit it out entirely -- were not to my liking. I invented a category that is common in many contests, but not this one. I would not be competitive in the formal categories, and that was okay. 

Contest within a contest

You have an amateur radio license. Provided you operate in accordance with that license your on air activity is yours to determine. When there is a contest underway you choose whether to participate and how to participate and who you work. You are under no obligation to participate in a manner that complies with the requirements of the sponsor's entry categories.

There are interesting examples that are more common than you might realize. For example, to only make contacts with unique multipliers. At the end of a contest your QSO and multiplier totals are equal. There are DXers who enjoy doing this since in global contests like CQ WW there are many contest DXpeditions and widespread interest that brings a lot of DX onto the bands. They have fun and don't care about their score in the actual contest.

Similarly, you might want to work as many stations as possible in just one country, or with call signs that end in the letter "D". Why? Why not! You can do whatever you like. Some clubs or groups of friends agree to a common set of rules and only compete against each other. They have fun and other contest participants benefit from the increased activity. The contest sponsor is uninvolved. It's perfectly legitimate fun.

I chose to enter the 20 meter single band, high power unlimited category -- SO20HP (A) -- in the ARRL DX SSB contest. However, the single band categories are all unassisted. Assistance forces you into the all band category. My reasons for doing it this way included:

• Time: By restricting myself to almost entirely daylight hours I could sleep normally and have time for other activities. At this point in the solar cycle, 20 meters opens around sunrise and closes about 2 hours after sunset. It worked for me since I find that SSB contests are less interesting than CW contests. SSB contests have unique challenges , some of which are listed below.
  
• Limited prospects on 10 and 15 meters: Again, for reasons of propagation, few DX contacts are possible on these bands. After chasing the available multipliers, at a painfully slow rate, there is little left to work.
• 40 meters is a morass: Almost all US activity is squeezed into 75 kHz from 7.125 to 7.200 MHz. There are a few ITU Region 2 stations operating above 7.2 MHz, but nothing in Region 1 or 2. Although Canadians can operate below 7.125 MHz most DX stations focus on that narrow 75 kHz window with the bulk potential contacts. The QRM is overwhelming and QSO potential is low. Some DX stations operate split to compensate. 
• Noise on 80 and 160 meters: SSB modulation has a wide bandwidth and thus a poor SNR. Except under exceptional propagation the rate of DX contacts is slow compared to CW. Staying up all night on the low bands hardly seemed worthwhile when I had no interest in being competitive.
• Station exercise: My best band at the moment is 20 meters. With all the challenges on the other bands I preferred to see what my antennas can do on 20. Despite a few problems with my antennas and antenna flexibility and a vintage amplifier that is not competitive, I believed I could do well. This was an opportunity to find out for sure.
  
• Practice being assisted: My preference is to operate unassisted in most contests. I need more practice being agile when new multipliers are spotted. For example, when during a high rate run of Europeans a needed multiplier in South America or Africa appears it is necessary to move quickly to avoid the inevitable pile up while not compromising the run or losing the run frequency by being absent too long. Just 20 to 30 seconds can be too long.

Those are my reasons and you will have your own to consider before a contest. The point is you can do what you want without feeling constrained by the categories offered by the contest sponsor. Of course if you do intend to be competitive you must fit yourself into a category and maximize your score for that chosen category. The decision is yours and yours alone.

How it went

To be competitive in my invented category I have to compare myself to the single band unassisted participants and to the 20 meter results on the all bands assisted participants. In those comparisons I am still a loser though not by a lot. I'm pretty happy with how I did. There is certainly room for improvement in my skills and the station. 

Propagation was one important factor. I am too far east and north in North America to place highly. A distance of a few hundred kilometers is enough to escape attenuation through the auroral zone. Stations in W2 and W3 had more success working Europe and further afield to Asia and the Pacific. VE1 and W1 have more daylight in common with Europe so that the opening lasts up to 1 hour longer. 

South is also a challenge. W2 and even those further southwest in VE3 often had a better shot to multipliers in the Caribbean and South America. I would get through, eventually, after those with more favourable propagation. I usually do better to the south on 15 meters under poor conditions since closer to the MUF the longer path to my latitude is favoured over those to the south. That isn't the case on 20.

Power is a problem. My vintage amplifier is well below our legal limit, which on SSB is 2250 watts PEP, or triple the 750 watt limit for constant carrier modes like CW. That puts me at a disadvantage that I keenly felt in the fiercer pile ups. I have a new amplifier on order that will fill that deficit.

The TH6 and TH7 tri-band yagis I rely on for most directions on 20 meters do not have the gain of long boom mono-band yagis. The 150' height of the TH7 is wonderful except when competing against those with bigger antenna farms. Due to in-shack control problems I am not able to easily rotate the upper 5-element 15 and 20 meter yagis of my stacks. Until that is properly dealt with they are usually left pointing at Europe.

There are always a maximum number of multipliers available on any band in a contest. Being assisted makes it possible to work all but a few of them. I worked 110 DXCC countries and the biggest guns did perhaps 10% better. In most cases I could not get through the pile ups due to the aforementioned reasons, or I was shy a few decibels to rise above the DX stations local noise.

Working multipliers is not always a hunt. By running on a clear frequency with a big signal most multipliers will find you. You will never work those stations by S & P (search and pounce). At times I was astonished by who called me. One rare multiplier in Africa called me on Sunday after I fruitlessly sat in their pile up the previous day. 

Another time I was startled when I starting being called by stations in southeast Asia with quite strong signals. In the midst of a European run I'd forgotten the band often opens briefly in that direction mid-morning. They weren't running so there was nothing seen on the spotting networks. It was delightful for a DXer like me to have that happen.

Other observations

After the CW version of the ARRL DX contest I used a text editor to extract all the contacts with QRP stations. This can be done easily because power is part of the exchange for non-W/VE. Accuracy is not high because some non-contesters instead send a serial number, their zone or whatever comes to mind. I filtered out those I could and came up with 2.3% of my 2400 contacts were with QRP stations. There were many more using 10 or 20 watts.

This interests me since I am a QRP enthusiast. That's how I returned to the hobby in 2013 and it has remained a passion. That I typically run much higher power nowadays does not diminish my interest in QRP. As a consequence I really enjoy being called by QRP stations in contests. With a big signal I know that I attract those with small antennas, low power or both.

You might expect that QRP would be less common in SSB contests due to the poorer SNR. This seems not to be the case. Although I didn't fully analyze my log the QRP percentage appears to be comparable. My furthest QRP contact was with Japan. That is not easy on 20 meters! I know because I've done only a few times myself when calling Japanese stations with just 5 watts.

Spotting networks are critical to success. Starting a run is slow because many stations click spots and don't tune with the VFO dial. I could monitor this in real time on the Telnet window. Within 30 seconds of seeing my call and frequency spotted the European pile up resumed. I once humourously referred to spots, human or CW skimmer, the QSO faerie.

The downside is that sometimes the spotted call is wrong. When I was spotted as VE2VN on Sunday, when everyone's rate had slowed considerably, I was deluged with dupe callers. For several minutes it was helpful to enunciate my call as Victor Echo 1-2-3 Victor Norway. Until spots aged out on most operators' software the dupe rates remained at 10% or so.

I used the contest to experiment with phonetics in my pre-recorded messages. While running I tried a shorter exchange: "five nine, oh en". This worked very well at first since regular contesters know that VE3 is Ontario (ON). Contest software will helpfully prefill the exchange accordingly. As the rate slowed and there were more casual contesters answering my CQ it caused problems. On Sunday I went back to using "five nine, oscar norway". Problem solved. 

My closing message was "thanks! victor echo three victor norway" and not the shorter "thanks! vee ee three victor norway". When I tried the latter in CQ WW SSB last fall it caused a surprising amount of confusion. This attempt to increase run rates didn't work out. I have always use full phonetics in the S & P message set.

Afterwards

My total operating time was under 17 hours. Had I operated long my score would have been higher. There was no point since my non-categorized entry would win nothing. I don't enjoy endlessly calling CQ or spinning the dial to hear nothing new. When that happens I take a break and find something else to do. I went so far as to take short breaks during the morning openings to Europe. To win it is necessary to practice BIC (butt in chair) and to keep the CQ machine going, no matter the propagation or the rate. Every QSO makes a difference.

There is a rumour that ARRL will expand the categories next year. That may not affect my behaviour since my focus on 20 meters this year might never be repeated. It's more likely that I'll do something completely different. Regardless, it'll be interesting to see what transpires.

I had fun in my own little contest, and that is what matters to me. I'd rather do these long contests as part of a multi-op, and I hope to be ready to do that later this year. It's not just the pandemic causing the delay since I have work to do to prepare the station for it. The work is ongoing. Indeed, that's why there's a long gap between the previous article and this one. I'm keeping busy and the whiff of spring antenna season is in the air.

So...You Want to Hold a Video Conference

Earlier this month our contest club (Contest Club Ontario) held a video conference. In the past we held smaller in-person outings with speakers this time of year. It takes more than one because VE3 is big -- 1500 km east-to-west just in the high population corridor -- and winter travel is not always possible or comfortable. 

With the popularity of Zoom and similar technology by various amateur radio clubs and groups we decided to give it a try. There was no other good option for a winter event due to the danger and proscription against gatherings of large groups. They are not the same type of event and planning for them is different. One big difference is that there is no catering; everyone provides their own meals and refreshments.

As the prime initiator and organizer of the event, and not an expert at these things, I gave us lots of time to prepare. I have participated at a few and presented at one. Other than that I have no experience with modern video conferencing services. I did lots of video business meetings years ago using point-to-point technology in purpose-built conference rooms.

Give yourself time

Our first step, way back in September, was to get agreement from the club executive with the rough outline of the event content and format. With that (and a Zoom Pro license) in hand we proceeded with the planning. I had concerns of my own to overcome along the way, and until those could be addressed the event was not formally announced.

Leaving the technology planning to others, I focussed on canvassing potential speakers. Asking for talk proposals turned up little. Most people are not comfortable with public speaking and although they have interesting things to say they will be reluctant. Don't push people. Give yourself time to solicit talks from knowledgable hams on topics that will be of interest to the audience.

Since we're a contest club that is what I focussed on. However it is generally true that enthusiastic contesters are also enthusiastic about DXing, exotic locales (hence multipliers) and big antennas. It was a good bet that what interested me would interest others. However, I was careful to reach out to others about topics that are of less interest to me personally. It is important to address your audience's interest where they differ from your own.

I am glad I gave us lots of time. Running up against reluctance to step forward I had to take the time to reach out to individuals and ask or persuade them to speak at the event. They then need the time to put a talk together. It may be a challenge if they've never done it before, or at least never in this format or to their friends and acquaintances rather than for their jobs.

Much to my chagrin, most of the talks ended up being about 160 meters. I didn't plan it that way, but when that's what I had I rolled along with it. It actually worked out well since 160 meters is a challenging band for most, winter is top band season and everyone lusts for the multipliers to boost their contest scores.

A critique

There are video conferences open to the public that attract thousands of hams to hear renowned speakers on a variety of topics. Of particular interest (to me) is Contest University. Their in-person conferences are recorded and available for viewing. Indeed, this has been going on for years before the pandemic fell upon us.

Despite the efforts of the organizers and speakers at those events, I have a few criticisms. As the audience broadens so does the content. There are too many canned presentations or ones that cater to the lowest common denominator. In other cases, the same speakers giving essentially the same talk are invited back time after time after time.

Most talks can be given once, and they should be left at that. For the good talks, record them and they can be watched forever by anyone. Repeating a live talk is pointless. Leave that for new material and new perspectives. Sticking the usual is laziness. Or perhaps they know their audience, because they do fill the seats.

Video conferences allow us to go far and wide for new content rather than leaning on the old reliable people. Leverage that and every video conference, local or global, can be better. This was my challenge for the CCO event: new and interesting content from speakers who may have never done it before.

Keep it local

When organizing an event for a local club, even one as geographically dispersed as the CCO, widely known and respected speakers from the larger events draw the eye. Avoid the temptation. 

Consider your local event to as a venue for your local heros. They're the ones with a profile that is more limited and yet are expert on topics that are of great interest. Reach out to them instead. Most hams love sharing their knowledge and helping others. Give them this opportunity. Everyone will benefit. For the especially shy, encourage them and help them along.

Going outside the local club is fine, and encouraged, but keep those numbers low. A pinch of exotic spice is nice provided you don't gorge. Don't give the implicit message that only outsiders have interesting things to say. Believe me, it isn't true. It may just be that you don't know them well. Reach out to those with a bigger or different network of local contacts and ask them for suggestions.

Don't stick to what you know or the topics that interest you. Cast a wider net. My contesting is almost solely on HF so I invited someone with extensive experience to speak about VHF/UHF contesting. It's different enough to be novel and with commonalities that make it understandable to the HFers.

Keep it local, but do direct consider external resources. If you know them and you need one more for your program, by all means make the invitation. A talk by a manufacturer can also be a great idea when the products are relevant to the audience.

Gauging interest

Keep the membership informed as the conference planning progresses, just don't write weekly status reports! Report only enough that everyone knows the plan is progressing. Nobody cares about the details that are consuming your time. When the program of speakers is confirmed, that is when you make the big announcement.

I did take a few steps to gauge interest while I was assembling the program. These included a couple of easy one-question surveys to elicit input on potential topics and conference organization. For example, when it appeared that I would have 6 speakers lined up I asked whether to schedule them in series or in two parallel streams. My worry was that doing it in series would make the program too long. I was also worried that parallel streams would be too technically complex for our neophyte team. 

The survey gave a large and resounding vote for talks in series. Unlike typical conferences, attendees can get up and stretch, grab a snack or skip a talk, and do so without being disruptive. Knowing this they opted to have the opportunity to see it all. Even though there is no direct human contact during the conference there is little appetite to watch recordings of talks after the conference.

A survey taken after the conference told me that we got the mix of topics about right and that there would be interest in doing a similar event in future. The message is to keep your membership involved and that will boost your confidence that you are doing the right thing. Feedback can also spur you to correct the plan that's straying from expectations.

Volunteers -- don't fly solo

Don't underestimate the complexity of running a conference like the one we did. Calling for volunteers to help out, especially individually, may make you uncomfortable but do it. You need moderators who can diplomatically manage the clock and feed questions to the speakers. Yes, we're amateurs, however it is important to treat this as if it is a professional conference. Keep it smooth.

One or two technically adept volunteers are needed to keep the conference running well. They are in the background and may not be immediately recognized so do highlight their contribution. Their jobs may include filtering joiners to see if they're on the invited list, forcing microphones to mute, recording the talks, fixing service glitches that may appear, and to interact with speakers off line to deal with any problems or emergencies.

Another constraint to how much I could accomplish was my internet service. It can barely keep up with the downstream audio and video. Upstream video was impossible. Even had I been adept enough to do more it would have been impossible. Don't underestimate the resource demands of Zoom and similar services.

You wouldn't operate a contest as SO3R if you've only ever operated SO1V. It won't go well so don't even try without lots of practice. Ask for assistance and don't try to be a hero. We received some priceless advice from others who've run similar events. Hams are friendly so reach out and ask.

Assembling a program

My first attempts to sign up speakers fell flat. Almost no one would consider volunteering. I was disappointed since I believed they were good choices because they have interesting things to say. As time went on and I got more rejections I also received hints about others that might be receptive. So I had their close contacts reach out to them or I solicited an introduction. This is no different than how I got things done in my professional career.

The result is that the program steered in a different direction than the one I had chosen. I accepted that and adjusted my expectations. Although this may seem disappointing it really wasn't. I had no assurance that my original plan would result in a good program. Sure, I believed it, but I could have been wrong. So I rolled with the changes. We ended up in a different place, and it was one that was quite interesting. As I mentioned above, 160 meters stole the program and yet it worked.

A couple of my intentionally solicited speakers worked out despite being a little out of the typical contester's interests. There were VHF/UHF contests and IOTA expeditions. Most contesters are focussed on HF and, although DX, island expeditions have different objectives. Stretching outside of the most people's comfort zone is okay if it is not overdone.

11:30 - 12:00  Open Mic
12:00 - 12:45  Rick VE3MM: 160/80 meter FCP vertical
12:45 -  1:30  Dana VE3DS: VHF/UHF contesting
 1:30 -  2:15  Steve VE6WZ: High-performance 160 meter remote
 2:15 -  3:00  Chris VO2AC/VE3FU: CQ 160 Expedition to VO2
 3:00 -  3:45  Cezar VE3LYC: TX0T and other IOTA Dxpeditions
 3:45 -  4:30  John VE3EJ: 160 meter 3-element vertical yagi
 4:30 -  5:00  AGM

Respect 

With so many people involved there are sure to be problems. Those issues are not always delivered politely. Yet it is absolutely necessary to deal with everyone respectfully. More often the messages that seem venomous are not intended that way. People may unintentionally come across badly when they are feel put out, ignored or not given the information or help they need or expect. 

Whether it is a volunteer, a speaker or a member of the audience it is important to put your own attitude aside and deal with each issue calmly and respectfully. Do that and the temperature quickly falls and further trouble is avoided. Questions get answered, remedial action taken if required and both sides exit the situation with at least a better understanding when the desired outcome isn't possible.

Respect goes further that just that. Recognize that the speakers and volunteers are generously giving of the time and talents. When they make a request, or a demand, deal with it promptly to the best of your ability. Don't be afraid to push back or to ask for time to deal with the matter. When you do so be respectful of them and their contribution to the event.

One example I encountered was trepidation about recording the talks and publishing them. Although this unwelcome request came from more than one of the speakers I pledged to honour the request. We recorded the sessions and afterward asked each for permission to publish their talk. Almost all agreed. That initial trepidation was assuaged by the success of the talks. Had the requests stood we would have erased the recordings.

As the organizer you may have your heart set on a particular outcome. In this instance I wanted the recordings as a record of the conference that attendees and others could enjoy and learn from afterward. I also saw it is a gift to the presenters as something they could point to and say, "I did that!" Nevertheless you must respect the wishes of those giving of themselves to make the conference successful. Although you can't always accommodate everyone, you should try.

Stepping back 

This isn't about you. When the time comes you need to step out of the spotlight and cede the stage to the speakers and volunteers you've assembled. You've done your job and everybody knows it. Never impose yourself on others when the audience wants to listen to others. 

Your role is to thank the speakers for putting in the time and effort to entertain and educate the audience members. Give explicit credit to the volunteers working in the background who are keeping the conference running in good order.

During my career I scorned managers who took credit for their employees' work and usurped the spotlight when presenting the work to executives and customers. I put my staff members in the spotlight, even if they were shy or uncertain about themselves.

There were times they were worried that I wouldn't get credit for all my effort to help bring their project to fruition. My response was to tell them not to worry about it because everyone is aware of my role. Putting them up front was good for them, and it was also good for me.

Don't hog the spotlight. If you do you'll loss most of the goodwill you've painstakingly gathered. Know when to step back and let others shine.

Looking back, and forward

Feedback on our conference has been very good. A post-conference survey indicates strong interest in doing it again next year. It will be interesting to see if the interest persists when in-person meetings are again possible. Despite the success of the video conference there is strong preference for meeting face-to-face.

In non-pandemic times we have two gatherings each year: a summer BBQ and winter lunches with club member speakers. These event have multiple objectives, however socializing is the primary driver. We are unlikely to try to squeeze a conference into them. In any case, many of the talks we had are more conveniently done by video. Speakers don't have to travel and we can reach a larger audience.

I have several months to ponder alternatives.

10 Meter Yagi Design: 5-elements on a 24' Boom

10 meter yagis are in my 2021 plan. These will be smaller than the long boom yagis I built for 15 and 20 meters last year. On a 24' boom, 5 elements on 10 meters has the same performance as a 5-element 20 meter yagi on a 48' boom, and that is certainly a huge antenna. Despite the relatively small size the performance is excellent.

Many hams in pursuit of ultimate performance take advantage of the smaller size and increase the boom length by 50% or more than 24'. Diminishing returns come into play so one should consider the trade offs. For example, 6 elements on a 36' boom (50% longer) has about 1 db more gain, a narrower beam width and a slightly broader SWR bandwidth. The wind load is substantially greater so the boom, truss and mast must be stronger, and that has a cost.

For the DXer the additional performance may be worthwhile. As a contester I would rather have a broader beam width, perhaps a little less F/B and acquire additional gain with stacking. The objectives are to increase the number of workable stations, punch hard into high population regions (Europe, Japan, US) and rapid direction switching. A stack of 2 or 3 individually rotatable and moderate size yagis is a good fit for my style of operating.

Don't reinvent the wheel

The time when we played with yagi designs to optimize them has passed. Computers and software optimization has replaced the excesses of uncertainty and experimentation, at least for mono-band rotatable yagis for the high bands. Sure, you can try it yourself but in the end you will almost certainly end up with a design that is little different from the many computer optimized designs that are already published. Wire yagis on the low bands are another matter with their broader range of design parameters, but here we're discussing 10 meter rotatable yagis.

What I do is to pick a published design and perhaps tweak it to get a little more gain or a little more bandwidth, depending on my need and the construction material on hand. When I do so there is often a performance metric that will degrade, if only slightly. Optimum designs really are optimum across all metrics. More often I will scale a yagi from one band to another, do the SDC (stepped diameter correction) for my tube taper schedule and element clamps, choose a matching network for the feed point and then build it.

This 10 meter antenna is right out of the ARRL Antenna Book. There are 5 elements on a 24' boom and it performs well from 28.0 to 28.9 MHz. Getting more bandwidth would require more elements and a longer boom, or giving up gain and F/B. There is no free lunch. As I described earlier, this design very nicely suits my particular objectives. That is, it's optimal in general and optimal for me.

Why would we need more bandwidth than 900 kHz? Having 900 kHz on 10 meters seems plenty yet there are times when more can be useful. Although I don't normally operate above 28.8 MHz, when the solar cycle is at maximum and there is a phone contest the activity extends above 29 MHz! Indeed, my first CQ WW SSB world #1 plaque in 2014 in the QRP category was due to an extraordinary run into Europe at a frequency above 29.1 MHz.

Now that I run higher power and my antennas are bigger there is less need to go quite so high in the band to find a frequency for running. I can compete in the more crowded and popular part of the band. That eventuality is a year away as the new solar cycle waxes.

Choosing tubes and calibrating the model

The tubing schedule for my home brew yagis is not what is typical of commercial antennas, due to cost or availability. As I've related in the past, that although Canada is awash in aluminum and aluminum products at reasonable prices, tubes of the alloy and sizes needed for telescoping yagi elements must often be imported at high prices. So I adapt by choosing alternatives and machine tubes as necessary to make them fit.

First I decide on the tubes and pipes to meet the requirements of survivability, cost and the ability to nest easily or with minimal machining. Next I sit in front of the computer and scale the yagi design for my selected element construction. Element taper has a modest though important effect on the reactance and therefore resonance. 

For this design my initial selection is 1" schedule 40 6061-T6 pipe 3'-4" long for the element centre. That may change when I compare the spot price this spring. The length is chosen to eliminate waste when cutting a 20' standard length pipe. The OD is 0.84" and the ID is 0.622", for a wall thickness of ~0.09". This is about the same strength and weight as nesting a ⅝" × 0.058" tube inside a ¾" × 0.58" tube, as specified in the ARRL Antenna Book. The pipe is easy to acquire locally. Reaming the pipe to nest a ⅝" tube is a quick job in my workshop with the 0.627" reamer in my toolbox. 

The ⅝" tube will be 2' long per half-element. For the usual 3" nesting, the net length is 21". Again, this is to eliminate waste from sectioning the 6' long tubes -- the standard length of aerospace aluminum alloy tubes is 12'. The element tips are ½" × 0.065" tubes. Boom construction will be decided by what material I can acquire surplus at a lower price than new tubes and pipes. Based on other designs I expect that a 2" × ⅛" wall tube or similar size pipe will support the antenna well in extreme weather.

Deviations that do not matter much for a single element antenna like a dipole become quite critical in a high performance yagi. Without taking the taper into consideration the yagi will still work though not nearly as well as it might. A little effort up front ensures that the time and effort you invest will pay dividends once the antenna is on the tower. This is not the place to be lazy or to take shortcuts. Mistakes happen, just as it did with my 15 meter yagis.

One of the easiest ways to calibrate the element with a published design is to model one element and determine its resonant frequency -- where X = 0. Do this in free space and without a boom. This is accurate for a yagi made of tubing and elements clamped to a plate sitting on the boom. The effect of the boom is a small fraction of the boom diameter. A yagi well above ground is effectively in free space, and therefore so are the elements. This is quite different from a one element antenna over real ground which will be affected by the ground.

I modelled the driven element per the ARRL Antenna Book and found a resonant frequency of ~28.85 MHz. Next I rebuilt the element with my selected tube schedule (it may change before it's built). I adjusted the ½" tips so that the resonant frequency was exactly the same. My half-elements are only ⅛" longer. It's chance that they agree so closely.

For such a small difference it is sufficiently accurate to arithmetic scale the half-elements by lengthening them by ⅛". For larger differences it is better to scale the elements geometrically. Do this by calculating the ratio of the original and scaled lengths and multiplying all the half-elements by that ratio. For exceptionally large differences or for elements with unique tapers an SDC must be redone for those elements by following the calibration procedure described above.

Model Performance

This is the boring part. The modelled antenna performs very much like the one in the ARRL Antenna Book. It is nevertheless a useful exercise to confirm that scaling had no deleterious effects and that the model is reliable.

The gain is very flat from 28 to 29 MHz. It rises from 10.1 dbi at the bottom of the band to peak at 10.6 dbi at 28.8 MHz. The slight 0.1 db gain drop at 29.0 MHz is mostly due to ohmic loss in the aluminum elements as the radiation resistance falls to a low value. There is little here to complain about.

The exceptional F/B is deceptive. There are rearward minor lobes that are worse. On balance, the directivity is very good. Perfection in all yagi performance metrics is impossible. 

Overall performance is excellent for a 10 meter yagi of this size. There was nothing found in this exercise that deters me from proceeding with construction of these antennas.

Feed point match

The 10 meter band is quite wide at 1.7 MHz. Put another way, the range is 6%. In comparison, 40 meters is 4% (7.0 to 7.3 MHz). We've seen before that it can be a challenge to match a 40 meter yagi across the entire band, and 10 meters is wider.

A full band match isn't necessary. For CW, SSB and digital modes it is sufficient to cover 28.0 to 29.0 MHz, or a little more than half the band. This is doable without special techniques such as OWA, with its requirement for an extra element as a coupled resonator the driven element. 

The SWR curve for this antenna shown in the ARRL Antenna Book is below 2 in this 1 MHz segment. I can live with that.

I have not decided on a matching network. I could use a gamma match, as I did for my 15 and 20 meter yagis, or I could use a beta (hairpin) match. The latter requires a split element that is isolated from the boom, and that involves additional work. Since the elements are substantially smaller it is less difficult to do this in a robust fashion. I have the fibreglass tubes to support the split elements and the u-bolt interiors for the element clamp can be covered in rubber. The rubber needs UV protection, and that is likely easier to achieve than machining suitable plastic stock.

The SWR bandwidth will be about the same with most conventional matching and feed systems. In the model I used a beta match since it is far easier to implement with NEC2 than a gamma match.

That's pretty good. The SWR remains low for a few hundred kHz below 28.0 and so it is tempting to shift the entire yagi upward. The downside is that the gain and F/B are poor at the lower frequencies. For my purposes it is preferable to maximize gain and directivity in the band segment of interest, and an SWR below 2 at up to 28.9 MHz is acceptable. I expect to rarely venture that high in the band.

Where they're going

My plan is for a stack on 10 meters, just as for 15 and 20 meters. The top yagi will go to the top of the mast on the 150' tower, where the 40 meter dipole is currently mounted. As my plan develops this tower will be primarily devoted to 40 and 10 meters, much the same as the 140' tower is for 20 and 15 meters. This is generally considered a good apportionment for two towers flexibility and minimal interaction for contests.

The lower 10 meter yagi is more difficult. Although it doesn't need to be too far beneath the upper yagi there are guys in the way. Even if its orientation is fixed the proximity of the upper guy set will have unwanted interactions, mostly of the non-resonant variety. Directivity will be impacted by the growth of the minor rear lobes. The degree of the interaction will have to be determined before the antennas are installed.

If it is to be rotatable then it must go lower to clear the guys. This would separate it from the top yagi by 30' to 50' (0.9λ to 1.5λ).

For 30' spacing the stack elevation pattern is good but not great. Although gain is a near perfect 3 db the nulls in either yagi are not entirely filled. It may be better to separate the yagis closer to the maximum of the range mentioned earlier. Alternatively a third yagi at a lower height would be even better, and supply additional gain.

I am undecided on the placement of the lower yagi. There are other antennas planned for the tower, including a 40 meter yagi. Further investigation is required.

Construction plan

I have no firm construction schedule as yet, other than wanting two of them on the tower by early autumn. In the spring I'll hunt for new and surplus material from my usual suppliers. These antennas will be easier to build than their larger cousins, the 15 and 20 meter 5-element yagis. That removes some of my worry about keeping to my plan for the year.

Measure Twice...

We all make mistakes, and with so many projects on the go I probably make more than most. Although it is easy enough to sweep them under the rug and move on that wouldn't be right. This blog isn't just about my successes. Mistakes are educational. I will share two that I recently discovered. 

Consider this an opportunity to learn, and perhaps you will be better prepared to avoid doing the same. With a small dollop of humility let's dive into these latest screw-ups.

Blazing the wrong trail

I mentioned in an article last month that I started clearing a path through the bush for the new east-west reversible Beverage. The west termination is a large tree within the tree line that separates the bush from a hay field. The tree line is also the home for the north-south reversible Beverage. From that tree there is another tree 140 meters due east that was my guide. The full length of the Beverage will be 160 meters.

I selected and surveyed the route with the help of a friend. Guided by a compass we spent a couple of hours picking the best route. Working on my own a few days later, I placed markers every 30 meters along the selected route. I spent several hours work spread over the next couple of weeks, again on my own, cutting down or trimming the bushes and trees that were directly under or too close to the route.

As I mentioned in that article, the path was not perfectly straight. I headed back into the bush to straighten the route. Armed with my compass I carefully sighted to the eastern tree. It wasn't due east. I played with the compass because it was very cold and I suspected that it was sticking. The tree remained stubbornly north of east. Slowly the truth of the matter seeped into my consciousness.

Not too far to the north there is a similar looking tree. I trudged through the snow and bushes and checked again. The tall tree in the distance was now exactly east of my position. I should have marked the tree rather than rely on memory. They all look alike to me. I emailed my friend to blame him for not coming over to check my work. He was not sympathetic.

Most of the desired path is either clear of big trees and, at the eastern end, there is cleared area I can still use. It is no disaster and the bush I cut has no value. It is new growth that naturally sprouted in what had been a tended field decades ago. 

I have more hours of work ahead before I can string the Beverage wire. That work is being delayed by higher priority projects, the pandemic and unseasonably cold weather.

Equivalent diameter of clamps

This one is an old mistake. I discovered it while designing the 10 meter yagis that are on my 2021 project plan. Discovering the mistake was a relief in a way because it explains an anomaly that I discussed on the blog over a year ago. At the time I put it down to a discrepancy between the software model and the physical antenna.

After adjusting the gamma match of the first 5-element 15 meter yagi the SWR curve was very good but not quite in accord with the model. The yagi was set 50 kHz higher than than the design. This was determined by the knee in the impedance curve at the top end of band. This is a good tell in most big yagis for where the antenna is centred because the impedance drops sharply as the frequency of maximum gain is approached.

A quick calculation led me to lengthen every half element by ¼". This small adjustment brought the measured SWR curve into agreement with the model. I thought no more of it at the time since the discrepancy was tiny and no software model perfect mirrors reality.

Recently I built a model for the 10 meter yagis that I plan to build and install later this year. The model deviated from the design in the ARRL Antenna Book. The error was small and at first I was prepared to adjust the element lengths and continue. A closer look revealed a puzzle.

I first modelled a single element using the published dimensions for the element and element-to-boom clamp. While copying the dimensions onto a model of a 15 meter yagi element (to save data entry) I noticed that the effective diameter I used from the 15 meter yagi was different from that in book. That was odd since the clamp design is the same except for the diameter of the centre tube. The 10 meter centre tube diameter in the ARRL Antenna Book is ¾" versus 1" for my 15 meter, yet the effective diameter shown in the book is larger. That isn't possible.

To be exact, my calculation for the 1" tube sitting directly on a 4" × ¼" plate was 1.637". The value in the book is 2.405". I was pretty sure the equations used were the same ones, coming from W6NL's derivation in his Physical Design of Yagi Antennas book (out of print). I wanted to check my calculation but I could find no record of it. It was time to open the book and start from scratch.

The diagram comes from Figure 9-2 in W6NL's book. There are several pages of diagrams and equations about many styles of element-to-boom clamp and the derivation of their respective diameters. Decades ago I used the equations produced by W2PV in his book Yagi Antenna Design (also long out of print). W6NL discusses those results and his, noting that although in most cases the difference is small it can be significant. It was time to sit down to work through the mathematics (again).

For the depicted clamp design the equations are straight-forward, though first appearances may be deceiving if, like many, you have a mathematics allergy. Look at each term in isolation and if you know any geometry at all you'll be able to figure out what's going on.

The area: A = πD²/4 + tW

The perimeter: P = πD + 2(W + t)

The effective radius: a_e = ½[SQRT(A/π) + P/(2π)]

The effective diameter: D_e = 2a_e

If you haven't yet figured it out, here's a hint. The area of the cross-section shown above is the sum of areas of a circle and a rectangle. The same is true of the perimeters. The effective radius is...mmm...sort of half the geometric mean or average of the two. The effective diameter comes from removing the halving operation. Clear as mud? Don't worry about it. It's an approximation that works well in practice, as Dave W6NL assures us.

Riffling through my files I found a spreadsheet with the W2PV equations. I had none for the revised W6NL equations so I added them to the spreadsheet. Having both the old and new equations serves as a sanity check. 

Note that the W2PV equations include saddles on the clamps that raise the tube above the plate. I don't have the equivalent for the W6NL equations. I don't need them, and most don't because it is typical to use heavy wall tube at the centre of the element. A u-bolt is sufficient to hold the tube without risk of crimping it and there is little danger of element slippage.

The value of 1.637" I previously calculated was far too low! I vaguely recall thinking that since the value is intermediate between the tube diameter and plate width it was probably correct. I did not confirm the calculation, not even checking against the W2PV equations spreadsheet.

The error affects the antenna in proportion to the length of the clamp and in inverse proportion to the wavelength. To confirm that my spreadsheet is generating correct results I entered the dimensions for those in the ARRL Antenna Book and I got almost exact agreement with the W6NL equations. 

The funny thing is that Dave Leeson himself pointed me to where I could find a spreadsheet with the equations. I did download it but since it was for an ancient bit of software and had to be converted I decided not to bother and did the calculation myself. I may have done with nothing fancier than a calculator. That was very foolish of me, and especially for not comparing my calculations with the correctly implemented W2PV equations.

With the error identified and corrected I returned to the model of the 5-element 15 meter yagi. Here is the SWR plot of the original design with the 1.637" erroneous equivalent diameter.

Keeping the element tips at their original length I modified the diameter of the 6" long clamps to the new 2.6" value. The SWR was again plotted across the band.

That is just about what I measured in the field and had to correct by lengthening the elements. Next I lengthened the element halves in the model by ¼", just as I did to tune the built antenna.

Lovely. There is no discrepancy between the model and the built antenna; the problem was human (ham) error. The software did exceptionally well to achieve accuracy far better than the misleading ¼" correction. I should learn to trust my software and the experts more than unverified calculations done by hand.

The enduring lesson: measure twice and adjust (or cut) once. As antennas grow larger these avoidable mistakes become more difficult to correct.

Eking Out the Decibels on 160 Meters

160 meters has a lot in common with VHF and UHF. Propagation effects are subtle and often there is no skip zone. This means that the farther the station, the weaker the received signal.

From day to day the signal strength of the same station varies a modest amount, and not to extremes we see with HF ionospheric propagation. If you can't work a station today there's a very good chance you can't work them tomorrow, or if you do it'll be marginal. Every decibel counts, even if you are patient and willing to wait for enhanced propagation. 

On HF,  due to the wide hourly, daily and monthly signal strength variation, you need only wait a little while for propagation to come your way. When it's good, QRP can work the world. When it's bad, a kilowatt and stacked yagis are not enough. Power and antenna gain certainly matter on HF for more reliable communication (and contest scores!), but for the casual operator it is usually acceptable to work what they can with the station they have.

Which brings me to the frustration of the CQ 160 contest last weekend. Overall the conditions were atrocious. It is in these conditions that every decibel counts when it comes to being heard. The small differences among stations -- antenna, power level -- made a large difference in the outcome.

When signals are close to the noise level even 1 decibel can make a large difference in whether a QSO can take place. When conditions are good that slight edge is nearly irrelevant: S7 and S7 + 1 db are indistinguishable.

Under the poor conditions prevailing during the contest only the very best stations and the most persistent operators did well when it came to working stations far away, whether it was across the ocean or across the continent. Success also requires good ears and high RDF receive antennas, however in this article I want to focus on the strength of the transmitted signal; that is, being heard far away.

Barring a change of QTH, there are several strategies available on 160 meters to improve transmit signal strength:

• Improve antenna effectiveness
• Improve antenna efficiency
• Increase antenna gain
• Increase power
• Wait for the other station's reception to improve

Antenna effectiveness

An effective antenna on 160 meters is difficult for the majority of hams. My first effective antenna went up in 2017 and I've been a ham for almost half a century. Many never have the opportunity. The wavelength is so long that it is difficult to have an antenna that is big enough or high enough.

An effective antenna is one that is compatible with the propagation mode and direction. With limited exceptions the most effective antenna on top band is a vertical. A horizontally polarized antenna, such as an inverted vee, is so low to the ground with respect to wavelength that it is very poor at low elevation angles, and like a vertical it is vulnerable to ground loss.

The 160 meter antennas of most hams are only moderately effective. For casual DXing it may be acceptable to wait, but in a contest waiting isn't an option. Unable to wait or raise a more effective antenna, the contester must focus on other strategies.

Antenna efficiency

An efficient antenna is one that radiates most of the applied power rather than dissipating it in the antenna or the local environment. Short antennas require loading or matching networks that can turn a large portion of the power into heat. Low horizontal antennas and vertical antennas lose a lot of power in the environment surrounding the antenna, most notably the ground. The wavelength is long so the antenna near field is large, with ample opportunity for loss.

A half size antenna (e.g. 20 meter high vertical) has a radiation resistance of several ohms. As a consequence, the ESR (equivalent series resistance) loss in loads, matching networks and ground can easily surpass 50%  (3 db) of the applied power. It is often far worse. For example, in my on-air tests of my short vertical (base matching of an 80 meter vertical) it is at least -6 db compared to my full size vertical.

For greatest efficiency the loading elements (coils, capacitance hats) should be far from the feed point and have the maximum Q (minimum ESR) we can attain. Inverted L and T antennas are examples of short verticals with large capacitance hats.

Verticals need a ground with the lowest possible ESR. This requires many on-ground radials or a smaller number of elevated radials. The elevation of the latter should be at least 10 meters or you'll still need lots of radials. As the vertical gets shorter, and the radiation resistance drops, the radial system becomes ever more critical. Unfortunately, an extensive radial system for a short vertical is often impractical, usually for the same reasons the vertical is short: not enough land.

For the same radial system, an antenna with gain will be less efficient because the gain is almost always accompanied by a lower radiation resistance. Efficiency on top band is never easy.

Antenna gain

Gain requires more than one antenna element. For those struggling to raise one antenna that is both effective and efficient, imagine how much more difficult it is to raise 2, 3 or 4 elements. It may be more than 2, 3 or 4 times more difficult. There is the increased land area, increased material quantity, pattern-destroying interactions with towers and buildings, and a switchable and complex network to phase, steer and match the array. 

The radial system for each element must be more extensive than for a one element antenna due to the lower radiation resistance. Otherwise the realizable gain will be reduced, calling into question the additional investment.

Should you decide to proceed, be prepared to achieve a maximum of 4 to 5 db. Getting beyond that will require an effort that only a handful have done. For example, a full size 4-square with 10,000 meters of radial wire. The simplest 2-element vertical array will net you no better than 3 db gain.

On top band, antenna gain does not come easily. It requires passion, time, money and land. Acres of land. The poorer the soil the more that must be invested in the radial system.

Power

Changes in the shack are always easier than changes outside. Wire an outlet, plug together a few more cables then browse the web site of your favourite ham retailer and click "Buy". A few days later you will see a 10 db boost to your transmit signal, on 160 meters and all the HF bands. 

This may not the cheapest path to a big signal but it is a dependable one. Many hams are old enough to have a little money saved up, so the purchase is within reach of most. You can't buy a 160 meter antenna that will get you anywhere close to the same improvement. Antennas must be built, while power can be bought.

You are not necessarily limited to 10 db. Starting with 100 watts that will take you to 1000 watts, and in many countries you can legally go beyond this by 2 db or so. I am sure you know hams who have not stopped there. I have been in shacks where a 4CX2500 is humming, and sometimes two of them. 

Many years ago I had an amp with a 4CX1500B and a stiff power supply that easily exceeded our legal limit. I rarely used it that way since that was back when home electronics were more susceptible to EMI. I chose to minimize friction with the neighbours. In any case, I didn't have an effective 160 meter antenna. I rarely operated on top band.

Unlike antenna improvements, boosting power is not reciprocal. Unless you invest in high RDF (directive) receive antennas the improvement may be wasted. We have all experienced the alligators with big signals and no ears. They're solid copy but respond to few. CQ machines only benefit the local electrical utility. But they do keep the shack warm through those long winter nights.

Other station's reception

Waiting for better propagation is always an option. Unfortunately, like Godot, it may never arrive. Hope is not a strategy. We need a more predictable outcome, whether it is during the heat of a contest or for chasing rare DX.

One semi-reliable method is to watch the sunrise terminator as it sweeps across the target. For a brief time, from a few minutes to half an hour, their noise level drops and the path remains open. The key on our end is the former: their receive SNR increases at their sunrise as atmospheric noise from the other direction, towards daylight, is attenuated by the re-ionization of the D layer.

I did not stay up until European sunrise either day of the contest. Those who did were able to work stations they could not work earlier. Of course I knew this might happen but I didn't think it worthwhile to stay up into the wee hours to win multipliers in a contest I was not competing in. 

A few decibels on the other end of the path can do wonders for your contest score or to put a new country into your top band log. Those decibels are a gift because you cannot buy them. When it happens you need to be there to receive the gift.

Summing up

The quickest route to being heard is more power. Going from 100 watts to 1000 watts is 10 db, and it is impractical for the majority to get anywhere near this from antenna improvements on 160 meters. If you're already using a small 800 watt amplifier, going to 1000 watts is 1 db, and even that small increase can be difficult to get from antenna work.

During the CQ 160 contest, with my Beverage receive antennas I heard far more DX stations than heard me. My enthusiasm to continue operating quickly waned since my top objective was to use the contest to work DX. A full size vertical with 8 radials didn't give me the edge I needed. 

With lots of effort I can squeeze a few more decibels from my 160 meter antenna. Some of that work I will certainly do, however I won't go to an extreme effort. I can already put plenty of contacts and multipliers in my contest log, and I am competitive in the pile ups. A better amplifier will suit me better.

Although I love antennas and antenna work this is one of those places where power rules. I am not saying that antenna work is pointless, just that the fastest, biggest and often the cheapest solution is more power. To be a top band big gun you must do both. There are no shortcuts.

In the end, you invest the time and money you want. After that, for most of us, you learn to appreciate what you have.

Beverage Selector: Initial Prototype

After building and installing my two reversible Beverage receive antennas and the remote switch to select the 4 directions (and expandable to 8) I wired up a simple switch arrangement at the operating desk to control the system. Temporary solutions do have a tendency to linger and I have been living with it and its limitations ever since. 

I have now made definitive steps towards a permanent control system for the operating desk. I modelled the home brew system based on the ergonomics of the control systems I've admired in the shacks of other low band aficionados. The prototype software is complete and the design of the enclosure and controls is almost done. Soon I'll be punching holes and putting it all together. 

Completion is still weeks away because there are several equally important projects filling my time. Rather than wait I thought it would be interesting to describe the design and the prototype so that you can see the project midstream. Too often when showing the final product many important steps and decision points are omitted, yet they are quite interesting to other prospective builders.

Design objectives

The design is focussed on ergonomics. It needs to fit comfortably on the operating desk among all the other paraphernalia needed for two keyboard SO2R. Room on the desktop is at a premium. I expanded the original plan to make use of the additional space on the sloped project box a friend (VE3WMB) gave me to include the 80 meter vertical yagi and control of high and low antenna combinations on all bands. 

It is not and will not become an antenna switch. This direction and high-low antenna selector works in concert with my existing controller for the 2 × 8 antenna switch. Automation will be added in due time.

The design objectives, as I originally conceived the selector:

• Fit comfortably on the operating desk, within easy reach and not crowded out other equipment
• Visual indication of where each antenna is pointed, and whether high or low antenna selected
• Sloped panel for maximum visibility when seated at the desk
• Big, fat buttons that are easy to see and hit when contest fatigue sets in 
• Visual indication of all selection modes so that mistakes are minimized
• Intuitive operation that does not require a manual
• Easy to switch between off/on and omni-directional/directional
• Compatible with future touch screen control
  

Enclosure design

The enclosure I was given constrains the design of the controls and construction. That isn't a bad thing! Ask any poet and they'll tell you that meter and rhyme help rather than hinder their creativity. I stared at the enclosure periodically over a few months until I could envision the complete design. Though not perfect (what is?) it is adequate to my objectives.

As you can see it's small but not tiny. If it is to be central the display will need to be 2" higher so that it fits beneath. Putting it on a transceiver, like the current manual antenna select, would reduce visibility of the sloping panel. I may move the rotary antenna switches on the vertical front face to keep all the controls in one place and eliminate one box. Until I have full automation that seems to be a reasonable compromise.

I used OpenOffice drawing software to experiment with the layout -- there are many other choices. It is critical that software dimension controls match what is printed. The rulers and dimension parameters for each object are very helpful to ensure proper alignment. All the sizes you see are exact for the parts to be used. I use squares to accurately and easily place button around their circles. The big buttons have LEDs built in; I purchased a selection of colours.

Each big circle is for a world map projection centred on my QTH with true bearings. Many sites around the internet will produce these for free, a donation or a small charge. I like the ones produced at the NS6T site. They are free (donation requested), visually appealing and the size is customizable.

There are several ways to plasticize the printed map and I am exploring those. I'll use paper until I settle on a durable format.

To control the high band stacks I will initially use 3-way switches (on-off-on) to select lower, upper or both. The LED colours are blue for upper (sky) and green for lower (ground), which I find intuitive and understandable with a quick glance.

Both upper and lower LEDs ought to be lit for both but for manual 12 VDC switching it is easier not to do so even though the logic is easy enough: !U for the lower LED and !L for the upper LED. Later I can wire these into the software to avoid extra logic and for remote control. I follow the same logic for 80 and 40 meter antennas even though they are not stacked. 

Switches for the 80 meter array select SSB and CW band segments and the antenna's 160 meter mode. These switches are software managed. Because the antenna is omni-directional on SSB the direction selection is disabled when SSB is selected. When SSB is added to the antenna the software is easily updated.

Another option is to substitute push buttons for the various switches. Pressing the button cycles through the available choices. For example, the stacks have 3 combinations. Hole size is approximately the same for buttons and switches so they can be changed later. Buttons all around can make operation simpler even when a button must be pressed twice. Software makes this flexibility easy to implement.

By printing the layout and taping it to the box various designs can be tested. Moving the drawing from the screen to the fingers is a useful means to verify that it works for you. Finally, the drawings are taped to the box as a drilling template.

Processor and software

I chose Arduino for this project. It's simple to use and program with the free IDE. Even the small Arduino Nano has more than adequate capacity for the Beverage controller. The greater though still modest complexity of Raspberry Pi isn't needed. The constraint isn't speed or memory: it's GPIO pins. 

The Beverage selector fits nicely on a Nano but to add the others requires the large GPIO count of an Arduino Mega. Alternatively, more than one Nano can be used: one for the 80 meter array and another for upper deck controllers. Multiple processors simplify the software and wiring at the cost of managing multiple Arduino sketches and downloading them. I have a Mega board so I will try it out.

For normal use no USB connection is needed. It is powered from a 12 (13.8) VDC for the remote antenna relays and, via a 5 VDC voltage regulator, the Arduino(s).

The main difficulty building the breadboard prototype for the Beverage selector is the quantity of LEDs and controls. There are 8 direction LEDs (top left), 5 relays (bottom right LEDs) and 8 push buttons. There are so many wires and LEDs I needed two breadboards. The sum (21) is more than the GPIO complement of the Arduino Nano.

To conserve GPIO pins the direction selector buttons connect to a single analogue GPIO pin. A resistors in a ring among the buttons comprise a voltage divider. When a button is pressed it puts a voltage in the range of 0 to 5 VDC on the analogue pin and converted to a digital value by the ADC.

The resistors are equal (220 Ω in the prototype) to ensure the voltage steps are near equal. The blue wire from A0 and resting at top centre is the "button". It is touched to a junction of the resistor ring to simulate a button push.

The picture shows the north direction has been selected. The LED at the top is for the button lamp. It's dim because I ran out of 220 Ω resistors and the GPIO high level is less than 5 VDC and is pulled down by LED current. The relay for the north-south Beverage is on (blue) and because south is the normal direction the reversing relay (red) is on.

A high value resistor (bottom left) from the pin to 5 VDC acts as a pull-up resistor that puts 5 VDC on the pin when no button is pressed. Although there are software selected pull-up resistors for the GPIO pins these are of uncertain value and we need one whose value is much greater than the sum of the resistor network. It is 33 kΩ only because that was the first suitable one I pulled from my resistor bin.

The Arduino code to interpret the analogue input is simple and reliable. ADC_MAX is 1023, the maximum value for a 10-bit ADC referenced to 5 VDC.

int buttonValue (int adcValue, int buttons) {
  if (adcValue < 0 || adcValue > ADC_MAX || buttons < 1) return -1;
  int difference = 1000;
  int button = -1;
  for (int i = 0; i <= buttons; i++) {
    int newDiff = abs(adcValue - i * (ADC_MAX / buttons));
    if (newDiff < difference) {
      difference = newDiff;
      button = i;
    }
  }
  if (button >= buttons) button = -1;
  return button;
}

Button presses are detected by periodic polling. Event driven (interrupts) are preferred but this is not practical on the Arduino, and not available on the Nano. There is a trade off among fast polling, processing cycles and human perception. As polling frequency increases the behaviour is closer to that of interrupts, which is good. Since the Arduino is doing nothing else this is not a problem, and the power dissipation penalty of the additional processing cycles is negligible. The prototype uses slow 100 ms polling (BUTTON_FSM_STEP) to aid debugging. That is slow enough for the polling rate to be noticed.

void loop() {
  int bevButtonSense = analogRead(BUTTONS_BEV_ADC);
  int bevButton = buttonValue (bevButtonSense, BUTTONS_BEV);
  bevButtonFsm (bevButton);
  delay(BUTTON_FSM_STEP);
}

A finite state machine (FSM) is used to interpret and act events. This is a common algorithmic technique that may be unfamiliar to many hobbyists. I'll omit the details in this discussion. The FSM debounces the buttons, differentiates short and long presses and controls the states of indicator LEDs and antenna relays. One FSM is needed for every selector: Beverages, 80 meter direction, 80 meter mode, stacks, etc. There's just the one for the Beverages in the prototype.

A short press is one that passes the debounce check and the button press is longer than 200 ms. A short press selects the direction and updates the state of the indicator LEDs and relays. A long press of 2000 ms on the currently selected direction turns off all the relays and LEDs. It is equivalent to an off switch. I like to have the relays off when I'm away from the shack. I will decrease the timers after the controller is complete. Others may prefer more relaxed time limits.

The prototype does not account for the processing between polling steps since it is brief. For more precise timing the software can use the Arduino clock to adjust the step time to compensate for processing time. A fast poll rate avoids this perception problem for short press and button hold times to improve system response for hasty operators such as myself.

const int BUTTONS_BEV_ADC = A0;
const int RELAY_BEV_NE = A1;
const int RELAY_BEV_S = A2;
const int RELAY_BEV_E = A3;
const int RELAY_BEV_SE = A4;
const int RELAY_BEV_REVERSE = A5;
int RELAY_BEV_PINS [RELAYS_BEV] = {RELAY_BEV_NE, RELAY_BEV_S,
  RELAY_BEV_E, RELAY_BEV_SE, RELAY_BEV_REVERSE};
int BUTTON_BEV_LEDS [BUTTONS_BEV] = {3, 4, 5, 6, 7, 8, 9, 10};
int BEV_RELAYS [BUTTONS_BEV] = {RELAY_BEV_S, RELAY_BEV_NE, RELAY_BEV_E,
  RELAY_BEV_SE, RELAY_BEV_S, RELAY_BEV_NE, RELAY_BEV_E, RELAY_BEV_SE};
int BEV_REVERSE [BUTTONS_BEV] = {true, false, false, false,
  false, true, true, true};

The GPIO pins and options are put into arrays and constants. This makes it easy to reassign pins without finding and editting each instance throughout the code. Clearing a set of LEDs and relays can be done with a single subroutine that is passed the array. 

Since not all 8 directions are currently installed I can substitute Beverages in the arrays for ones that are closest. For example, to choose northwest the north Beverage can be selected until the southeast-northwest Beverage is actually built. The northwest or north indicator LED can be lit per your preference. I haven't decided which.

I am using several of the analogue pins as digital outputs, which the Arduino allows and is needed because there are insufficient digital pins on the Nano. The 'An' values are numeric constants above those of the digital GPIO pins. The values are different on different Arduino processors so the constant names should always be used in preference to their integer values.

Solid state switching

I don't like the sound of clacking relays in the shack. For the Beverage controller there will be a lot of that as I cycle through the directions on every CQ to pull weak signals out of the noise. The GPIO pins cannot directly drive the 12 VDC relays in the remote switches so local switching peripherals are needed.

Opto-isolated relays are commonly used since they're inexpensive and widely available. They're also noisy, bulky and overkill for switching currents of well below 1 A. I've operated at stations where a band change is startling because of the all the clacking relays that switch antennas, amplifiers and filters. I want a quiet, compact solid state solution.

One giant hole in my education is solid state theory and circuit design. I have always relied on circuits designed by others or made do with the simplest of circuits for my needs. Often I can troubleshoot solid state equipment since you don't need a lot of the theory. The lack is a problem because the commercial products for solid state switching are unsuitable and designing switches from discrete components is a challenging exercise for me.

My home brew switches are high side, where the relays are grounded and they are powered by placing 12 VDC on the control lines. Solid state high side switches are more difficult to design than low side switches, which should be low loss and must prevent the high relay voltage appearing on the GPIO pins and thereby destroy the microprocessor.

I educated myself from what I could find on the internet. Finding simple yet sensible design advice was not easy. Most is vague or far too technical. 

Once I settled on an approach I purchased parts to experiment with. Candidate circuits were built and adjusted on a breadboard until I got the performance I wanted. The circuit at right is successfully emulating a relay switch for the reversing relay GPIO pin. It is shown operating at 5 VDC and it has been successfully tested at 12 VDC. I have yet to test it with the full range of load currents it will have to deal with in my station.

High side solid state switching for GPIO pins is an interesting topic that deserves an article of its own. Look for it within the next month.

Construction

Other than a long list of projects to do the prototype is done and construction of the final product can proceed. It's difficult to predict when it'll be done, other than I am determined to have it in use before the end of the winter 160 meter season. 

When it's complete and in use for a while another article will follow to describe the controller in its entirety. I may make the final Arduino sketch available if there's interest.