Tuning and Switching the New 15 Meter Yagi

The new 3-element 15 meter yagi is installed along with its tower bracket, and it is tuned and working. It took finesse to guide the yagi along the tram line between several obstructions to reach its final position. There were just two of us needed for the operation, me and Dave VE3KG. 

The tram line itself was a exercise in choreography since setting it up (and removing it) requires hauling lines up the tower, moving each around the many obstructions on the tower, clearing it over the director end of the large 5-element 20 meter yagi (lower yagi of the stack, fixed on Europe) and attaching it to a winch anchored at the base of the other large tower -- the towers are 200' (60 m) apart.

If everything goes right this can all be done myself. That would be a foolish bet, hence Dave's welcome presence. 

There are no pictures of the tram or yagi raising. There are so many articles about trams in this blog that it would be largely superfluous. If you want to learn more, type "tram" into the search box and you will be amply rewarded.

One item that I'll note is that the tram was anchored high on tower, just below the rotatable 5-element 15 meter yagi. That is above the long "false mast" built for this antenna. Once the new yagi was comfortably past the elements of the big 20 meter yagi the tram line was slackened and the haul rope reversed to lower the antenna to the bottom of the false mast.

As noted in the construction article this antenna is very lightweight. One person can easily pull it up the tram line. Most of our time was spent frequently stopping and checking our progress to ensure that nothing would tangle. It is surprisingly difficult to gain a full 3D perspective of the arrangement just by walking around on the ground and looking up. 

From long experience I understand the necessity of proceeding in small steps to be certain what's really going on up there. With more ground crew I could have positioned myself on the tower for a better perspective and guide the operation with full confidence.

The picture shows the yagi installed on the bracket and pointing south. The 5-element 20 and 15 meter stacks are pointed northeast (to Europe).

Let's talk about the tower brackets. They secure the two ends of the false mast and were made from metal I had in stock. The tower attachment is unique to the LR20 guyed towers that I have. There are girts approximately every 5' (two per 10' section) for attaching guys or equipment. Other towers have their unique attachment requirements so a detailed discussion won't be too useful to most readers. Similar brackets for my towers have been discussed in detail in previous articles. 

The lower bracket bears the weight of the mast and antennas so it must be built accordingly. It is ⅜" × 3" aluminum alloy angle stock. It was obtained free and includes a variety of holes from its original commercial tower application. I've used more of this material for other side mount brackets. I'm happy to have it now that aluminum prices have soared.

An offset vertical load creates significant shear stress on the bracket, tower girt and connecting hardware. While not A325, the ½" grade 5 bolts tying the bracket to the tower girt have an unthreaded shank where they pass through the bracket and girt. Bolts are weaker in shear at the threads. I can stand on the end of the bracket and jump up and down. I did just that and it didn't flex. The upper bracket has no shear load so it can be less bulky. The galvanized angle I selected for it was ideal for the job, but not for dancing.

The brackets were carried up by me and then the mast pulled up with the same rope that was later used to haul the yagi. I did this work myself at the cost of a couple of extra climbs. I don't call in favours for small jobs, leaving that for bigger ones that should never be attempted alone. 

The false mast spans 10' to fit another yagi to be fixed south; it's long enough to require 2 pictures. I am considering additional antennas for it but there is no rush. The interaction models are guiding me in this and there is a lot to consider. It is worthy of an article on its own due to the complexity and performance implications. Look for that article before the end of the year. 

For now I will mention that there is interaction among the yagis -- the new yagi sandwiched between 5-element 15 and 20 meter yagis -- but that it is quite small and therefore acceptable. The 15 and 20 meter 5-element yagis are negligibly affected by the presence of the new yagi positioned between them.

Notice the stop bolt under the mast. It is the primary path for transferring the vertical load to the bracket and tower. The saddle clamps only need to keep the mast from rotating. This is preferable where it can be accommodated. Without a stop bolt more saddle clamps can be deployed to deal with the vertical shear load; I use 4 better quality saddle clamps on the boom-to-mast clamps of my large yagis. Common saddle clamps (muffler clamps) found in hardware stores are not designed for shear loads so choose your hardware with care.

The dacron rope boom truss is simply tied to a clamp on the false mast. I probably could have forgone the truss entirely since there is very little sag. It is good insurance nevertheless. I didn't get a close up of the 15 meter truss anchor so here's a picture of one on the 3-element 20 meter yagi. A thimble avoids the risk of steel edges cutting the. A copper wire clip ensures that the granny knots can't unravel. I was never a boy scout so I keep my knots simple.

Turnbuckles are eschewed. I simply pull the rope tight at the mast clamp, tie the knots and then clip the rope. Both yagis are lightweight so this method is simple, effective and cheap. It only takes a minute to level the boom.

Unlike for the 20 meter yagi, I skipped a separate lift to test and tune the yagi. I didn't anticipate any surprises. Initial tuning of the gamma match after it was secured to the mast took only a few minutes. It was to confirm that nothing was amiss in the design or construction. A few days later I did a more precise tuning that brought the SWR to nearly 1 at mid-band (21.225 MHz). At 21 MHz the SWR is 1.3 and at 21.450 MHz it's 1.6. That's very close to what was calculated for the EZNEC model using both NEC2 and NEC5.

Initial modelling of interactions indicates that the 5-element 20 meter below it does not significantly degrade pattern, gain or match. The tower guys are far enough that any interaction should be minor. However I did not check that in the model. There is interaction with the 5-element 15 meter yagi ~20' higher that skews the pattern but does not affect gain or the match. 

I'll address the full suite of yagi interactions in a forthcoming article rather than deal with it here.  

I do not need a separate transmission line for the yagi. I built a simple auxiliary antenna switch using an SPDT relay and mounted it directly on top of the existing Heliax LDF5 transmission line for the 15 meter stack. The NC (normally closed) port connects to the jumper going to the stack switch further up the tower; the top of the Heliax is about 107' above ground and the stack switch is at 130'. An LMR400 jumper runs down the tower to the 3-element yagi that's at about 87'. There's extra so I wound it into a several turn scramble wound CMC (common mode choke). I'll improve it later. Maybe.

Notice that the enclosure (2-piece aluminum) is oriented to place the gaps between the halves at the bottom. That makes a natural path for moisture to escape without the need for weep holes. 

The wire to power the relay is less than 10' long to where is is spliced into a Cat5 control cable at the lower bracket for the 5-element 15 meter yagi (lower yagi of the stack and partially rotatable). A few more splices from there back to the shack and a change to the antenna selection software put the antenna in the list of available antennas for 15 meters. 

Back in the shack I gave the antenna a spin on 15 meters and compared it to south-pointing TH6 on the other tower and at a similar height and the rotatable Skyhawk a little lower at about 71'. I found several W4, Caribbean and South American stations to compare the yagis. One comparison session isn't enough to do a full evaluation since the elevation angle of propagation varies with time of day and the season, and can differ from one day to the next. 

Overall the 3-element yagi was the best of the group. The TH6 came reasonably close but seemed up to a few decibels worse. The Skyhawk was sometimes equal and other times worse, probably due to its lower height. The TH6 and Skyhawk both have 4 active elements on 6 meters, but a couple of the TH6 elements utilize traps on 15 meters that lower the efficiency and the multi-band design of the Skyhawk necessarily limits the achievable gain by 1 or 2 db.

It's interesting that the comparison can't be a rapid A-B-C sequence. Due to their different locations the cyclical QSB was not in phase. I had to monitor the waning and waxing of signal strength through a full cycle before switching to the next antenna. You would have to take the same care when transmitting and comparing the reports from RBN and WSPR networks. 

On balance I'm pretty happy with the new yagi so far. It takes 1000 watts without complaint. The real test will be in a contest, perhaps CQ WW CW where it will be used in preference to the TH6 to snag multipliers in the Caribbean and South America. South is not a direction where I want to park the large yagis since that direction is not a source of many contacts, just the occasional mult.

I'll close with views from the new antenna after the final tuning of the gamma match. Why not, it was a gorgeous fall day with the trees in full colour. On the top is north (rear) view. In the near distance you can see the Skyhawk tri-band yagi a few meters lower. On the bottom is the south (front) view. There's a pretty clear shot in that direction and the two higher guy sets are off to the side of the frame. You can guess where they are from the position of the north guys in the first picture.

With this job out of the way it was on to the next item on my long to-do list, not least of which is raising the 3-element 20 meter yagi. It's a shame that the new antennas weren't ready for the CQ WW SSB contest. There are only so many hours in each day and the TH6 was already available for the southern multipliers. I am getting closer to being in a position to retire the south-pointing TH6 and be free of its interaction woes and narrow bandwidth.

FT8: Passive Entertainment?

On Sunday evening after CQ WW SSB finished the bands became eerily quiet, on both CW and SSB. That's typical because quite a lot of the daily chatter on the bands is by contesters, and they understandably shut down at 2359Z to eat and rest. Since I made an unserious contest effort I was not tired. Finding little to interest me I drifted over to 3573 kHz and fired up WS Digital Mode Suite (the former WSJT-X Improved).

There were a few Africans on so I worked one and then called another, C5R. I couldn't work him. He heard me fine but I couldn't decode his somewhat weak signal after that initial message sequence.

There's the rub. I am decoding nothing, that's the software's job. While it records and decodes signals in the passband I sit, watch and wait. I have no influence at all over whether a signal successfully decodes. The decode can fail for any of several reasons: QRM, fading, distortion, receiver issues, etc. All that I (really, the software) can do is repeat a message until a reply is received and decoded.

In this case it was QRM. A couple of NA stations would start transmitting with far stronger signals that overlapped C5R. I doubt that any harm was meant, only that they didn't hear his relatively weak signal while I have a very effective directional vertical yagi on 80 meters.

All I could do was watch while my report to him repeated several times without a decoded response. I could see his signal partially exposed next to the stronger stations on the waterfall display so I knew he was transmitted. Yet there was nothing I could do except give up, so that's what I did. The same thing happened a little later. I didn't try a third time. He may have been wondering what was going on.

That's the issue I have with these digital modes. On CW or SSB it is possible to interact with the station to try and find a way to complete the QSO, or to quickly QSY and ask the interfering station to move. It is possible though awkward to compose a custom message in WSJT-X, which I never do. Maybe he wouldn't move anyway or just not understand what I wanted from the very short message that the software allows.

There is another reason I prefer the traditional modes: pile ups. On digital modes all you can do is call and hope that the DX picks your call out of dozens. Worse, you might not be decoded at all due to the QRM. You can't easily hear others on or near your frequency due to enforced transmission intervals that are precisely identical. You can't listen without losing at least half a minute.

For FT8 pile ups it's: little pistols beware! In the past I've written many articles about CW pile up techniques that can allow even the smallest station to get through. Here's an old article from when I got through a big pile up on a DXpedition using QRP. Skill counts for a great deal on CW, to a lesser extent on SSB, and not so much on digital. On the other hand, luck can be a friend to the little pistol on FT8 if the DX happens to click on your call.

FT8 and its sibling digital modes are just too passive for my taste. Skill and interaction count for so little. I am not too concerned with the software decoding but with the inability to be more actively involved in a challenging QSO. That's one reason I am not attracted to digital modes other than a few cases. One of those is 6 meters, where it does wonderfully, and occasionally on 160 meters when CW activity is sparse or absent, a common occurrence. I might also work rare DX on digital as insurance in case they don't appear on CW. I'm not a traditional modes snob.

On the other hand, the passivity of FT8 can be relaxing after a hard fought contest or a busy day at work. FT8 can be the active ham's alternative to television or doom scrolling. Have a seat and let the activity wash over you. There's nothing wrong with that, if kept in moderation.

An incomplete FT8 QSO is no disaster. You move on to the next station while hoping to work them another time, whether a few minutes later or next week. That can happen for any mode. Unfortunately there is nothing much you can practice to hone your skills on digital modes since circumstances dominate the probability of success.

Keep your perspective and don't punch the computer or curse the oblivious interfering stations. It won't do any good. It's just one QSO out of many thousands you'll make over your ham career. When I get frustrated I spend some time on CW or SSB where I have more control, more agency over the results.

Oops! Repairing a Broken Guy Anchor Rod

In a previous article I teased a picture showing a small pit dug up in the 80 meter vertical antenna field. As I said, I had an accident with a tractor. It was careless of me to let the vegetation grow high and then not mark the guy anchor rods, which poke up only a few inches above grade, and then fail to watch for them when I'm working in the field. 

The new anchors were installed a year ago as the first step in rebuilding the 80 meter array. I have been proceeding in steps and I hope to replace the tower this year, as time and weather allow. A consequence of my slow schedule is that the guy anchors are so far unused and have no attachments to make them particularly visible. They were vulnerable.

Guy anchor rods are designed to be strong in tension. They are not typically designed to withstand an impact from the side. The soil can be a poor support for a long steel strut projecting from a deeply buried concrete guy anchor. Hardened steel driven by many horsepower via a reduction drive can do a lot of damage. 

The vulnerability to impacts leads some commercial tower sites to construct concrete or steel bollards on either side of guy anchors to prevent accidental collisions with vehicles and heavy equipment. These incidents can and have occurred.

Since I want to rebuild the central tower this fall the anchor needed to be repaired. It is not as difficult as it might seem but must be done properly if it is to have at least the strength of the original. The steps were as follows:

1. Dig down to inspect the damage
2. Assess the point below which the rod is undamaged
3. Cut the rod at the transition between damaged and undamaged
4. Fabricate an extension rod that overlaps and is joined to the remaining rod
5. Align the rod extension (azimuth and elevation angle) to the original spec
6. Coat the new and old rod to prevent corrosion
7. Backfill the hole and compact the soil
8. Confirm that the rod is still aligned

In the worst case, there is not enough undamaged rod to splice to or too deep to effect repairs. This is not a large anchor or very deep, but I was happy not to have to remove it and make a new one. After cutting off half the rod there was enough left to work with it.

After performing steps 1 and 2 last month I included a new extension rod on my shopping list when I visited the metal yard. Since I had to cut 2' (60 cm) down, the extension had to be at least 2.5' (75 cm) to account for overlap to make the splice. Splicing angle stock is far easier than for round anchor rods. The extension is wider (2.5" vs 2") and thicker (3/16" vs ⅛") to make the repair easier and a little stronger than the original.

I used a short straight edge in step 3. I slid it up and down the rod to precisely determine where the steel began to curve. The objective was to preserve as much of the original as possible to make the repair easier. If the cut is too far down it may be impossible to work on with hand and power tools other than by making the excavation wider and thus significantly more toil with a shovel. 

Do not attempt to straighten the bent rod! This will in most cases weaken the steel, especially if it is tempered to any degree. Even mild steel can be weakened when bent. Steel is inexpensive so don't try to "cheap" your way out of this problem.

I had to cut a radial while digging since it was in the way of the repair work. I was able to keep the radial intact and running over the excavation when the anchor was installed last year since I didn't need to fit tools down there. It can be spliced after the repair is complete.

I scooped out ~2 ft² of soil around the shortened rod to fit tools for the repair work: a hacksaw to cut off the damaged part and a drill to make the splice holes to join the new section to the old. The paint on the old one was damaged during digging and had to be repaired as well. That required washing and drying the surface before applying new paint coats. For convenience I used cold galvanizing compound since it dries faster than rust prevention paint. Since the painting must be done outdoors pay close attention to the temperature range specified for the product. I painted the extension indoors where it is warm.

The exact positions of the splice holes is not critical which is great because precision is difficult when working in the tight space. Holes should be set back from from the edges and far enough apart that the upper section can't wobble. Assuming the remnant is correctly aligned, the new extension should also be aligned. Notice that the larger extension is placed behind the remnant to make maximum use of the available surface area. The cut and drilled holes are filed and reamed to remove metal ridges that would prevent the pieces from sitting flat against each other. 

Support the upper end of the extension with a piece of lumber as shown at right. Sight the extension to confirm that it is lined up with the tower (azimuth angle) and use an inclinometer for the elevation angle. Don't rely only on the clamps and the trueness of the metal.

⅛" pilot holes are drilled first in the remnant. Next I firmly mated the extension to the remnant with small C-clamps (one on each face) and continued the pilot holes by drilling through the extension. I separated the sections and widened the holes to accommodate 5/16" grade 5 fasteners. 

Drilling in the hole is awkward and it can be difficult to apply pressure on the bit on axis and without wobble or bending. Don't rush it and wear eye protection! You could shatter the bit and fling fragments into your eyes. Widening the holes with a large bit is much easier than drilling the pilot holes. Holes in the extension can be widened on site or on a drill press. I found it easier to do all the drilling on site. I hope it is obvious that the drill bits should be of suitable type and quality, and sharp enough that they cut quickly without wandering. Use coolant on large bits cutting through steel or you can ruin them.

When I was done the alignment of the repaired anchor rod was within 1°. That's pretty well perfect, and stayed correctly aligned when the lumber support was removed. I spray painted the hardware and let the pieces dry overnight. Then I backfilled the hole while compacting it, paying particular attention to the underside of the repaired anchor rod. However, don't tamp too aggressively since you might alter the alignment or scrape the paint. Guy wire tension can correct a misalignment but it's better to keep the rod aligned throughout the job.

The backfilled hole and rod looked great when I was done. I just had to be careful to keep the broken ends of the cut radial from being buried. After several years they get "absorbed" by the vegetation and might be difficult to find later when you want to splice them together.

The rebuild of the 80 meter tower won't happen in October. I hope to do that in November while the weather is still warm enough for concrete work. There are other priorities at the moment.

Amateur Radio is a Small Market

Another item on my 2026 list has been checked off: a new solid state, broadband amplifier.

It will take some time for me to become familiarized with the amp and properly integrate with the rest of the station. At the moment it is sitting on top of the Acom 1500, which is convenient for initial testing and there are no air vents on the underside to be blocked. The 4O3A PGXL is deeper (back to front) than most other equipment but not wider or higher, and it is lighter than typical tube amps.

This is an expensive product. There are cheaper amps but, overall, despite the price and some aspects of it that I dislike it is on balance the right amp for me. The choice was determined by my operating preferences and is not an endorsement. I won't be telling you whether it is the right or wrong choice for you. 

While I proceed with getting the amp set up I want to use the opportunity of this purchase to talk about a broader topic: the amateur radio equipment market. Although there are many of us around the world we are a small market, and very small when it comes to high-end specialized equipment. This includes transceivers and amplifiers, but especially products for narrow interests such as sophisticated switching systems for SO2R and multi-op contests, BPF, big HF yagis and receive antenna arrays, contest software and more. 

I find that many hams are surprised by how few employees and revenue the major brand names have in their ham radio product teams. They're well known brand names to us but are mostly small to medium size businesses. When the founder/operator of a small brand retires the company more than often than not is wound down, not sold. For large companies, like Kenwood, ham radio is just one division among many. That is helpful with respect to marketing and technology but small divisions don't impress much at the CEO level.

There aren't many of us to sustain commercial companies -- manufacturers, dealers and service centres -- on the basis of numbers alone. Manufacturers have a challenge amortizing upfront and ongoing development costs and providing service for products with production runs in the low thousands or even hundreds. For some it is a labour of love and may be born out of necessity when an entrepreneur sees a need for themselves and decides to turn their unique builds into products. 

We are fortunate that there are as many products as there are, and that we have the option not to build our own. For the most sophisticated modern equipment, building your own is almost never possible.

I'll use this amplifier purchase as an example of manufacture and distribution of a high-end amateur radio product with few sales. It was an interesting journey. Please take note: although a few of the points are politics adjacent this is not a political article. If you take offense easily you should stop reading now to keep your blood pressure stable.

1) Buy local preferred

Few of the major product categories found in our hobby are made in Canada. There have been more in the past but companies come and go. About the only product in my station that falls into the high-end category are the BPF (band pass filters) from Pavel VA6AM. His products are widely lauded yet it is a one-man shop. BPF for contesters is a small market that he likely can't live on alone. He has a day job.

Kilowatt class HF amplifiers are built in Japan, US, EU and a few other places. For example, Icom, Yaesu, 4O3A, Omron, Acom, RF Power, Elecraft, SPE, Flex and Mercury. Each has features that appeal to some and not others. None sell many of them. Quite a few hams get by with previously enjoyed tube equipment from decades past. I have one of those: the Drake L7. 

No amplifier in this class is currently made in Canada despite being no more difficult to do it here than elsewhere. Since the Canadian amateur radio market is too small to build a business and offer competitive prices any prospective entrepreneur would have to market globally.

2) Domestic dealers

I have to buy an amp made elsewhere but I'd like to buy it from a dealer in Canada to ease the purchase and any future service. However, finding a dealer or service in Canada for any of these products is challenging. They naturally gravitate to the nearby far larger US market. That can still be convenient but not always, and less so at this time in history.

There was one dealer for the PGXL in Canada that came as part of the partnership between Flex and 4O3A. While I know none of the details there appear to be a few fractures. One consequence is that PGXL is no longer sold by that dealer. I spoke to them to ask why. It came down to poor sales prospects for a high-end product. You can only negotiate a lower price with the manufacturer when you commit to higher sales volume and buy in bulk, not one by one.

The bottom line is that they'd love to keep selling the PGXL but without Flex in the deal it is not possible to negotiate a price that allows them to be competitive. I can certainly understand that. But it meant that I'd have to look elsewhere, and that elsewhere is outside the country.

3) Foreign dealers

There is one 4O3A dealer in North America: DX Engineering. They're a great company to deal with in most cases and they make it easy for Canadian hams to purchase products from them. There is never a need to cross the border, whether to buy, return or get warranty service (not all products). 

They have two things working against them in this instance: cross-border politics (hopefully short term only) and a 10% tariff for products entering the US from Europe. The tariff is not rebated for sales outside of the US. 

Although not anyone's fault, cross-border high priced items trigger credit card fraud algorithms. While I appreciate the intent, it's time consuming to get purchases of this nature approved. Many calls are needed, and these days involve getting past the AI "front desk".

Other amplifier companies may locate their NA distribution in the US, or have none at all. They don't often locate here. Few of the US-based dealers and manufacturers go out of their way to sell beyond the continental US, whether it's to other countries or offshore US states and territories. They find the process and associated costs too bothersome. The continental US is enough of a market for them. It's an understandable business strategy even if some money is left on the table.

There are many companies that will provide a US shipping address right across the border where we can pick up shipments or they will transfer across to our side of the border for a fee. That makes it easy to buy, but there's a greater cost and I don't want the expense and inconvenience of conveying products across the border myself whether for the initial purchase or possible future repairs. It is not surprising, because of how the amateur radio market is structured, that I know many Canadian hams that go this route. It is also done when buying used equipment from American hams. A friend of mine bought a used PGXL by meeting the selling ham across the border.

Unhappy with these options I set about exploring other PGXL dealers. I focussed on Europe since that is really the only good alternative for us outside NA. I have no experience buying this class of products from Europe so I made a few inquiries and looked online.

In summary, the prices are not lower. It was a surprise considering that the manufacturer is in Europe and these are European dealers. However, Montenegro is not in the EU and that probably affects prices. Even accounting for that, the cost of doing business in Europe is typically higher than here. Subtracting the VAT, which is not charged for international sales, didn't bring the prices down low enough to be attractive.

A friend of mine with contacts made an inquiry for me and found that, yes, I could order direct from the company. I looked at shipping and insurance and considered the higher commercial risk, and that manufacturers are loath to undercut their dealers' prices. That ended my search for a better deal from a foreign dealer. 

I went ahead and bought the amplifier from DX Engineering. With the included 10% Europe-to-US tariff it was still a favourable price and service prospects are better. It arrived quickly but with an unwelcome substitution. To their credit they shipped the correct power cord very quickly without a fuss. Less than 2 weeks after placing my order the amp was powered up and making contacts.

4) Post-sales service

Local service is almost never an option. I remember in my youth (early 1970s) taking a busted ham band tube receiver to a TV repair shop owned by a friend of my father. My electronics knowledge was still nascent and I didn't own any test equipment, which I couldn't afford. Their techs looked at it from time to time for the two weeks they held on to it but wisely chose not to delve deeper. It was beyond their knowledge base. 

Amateur radio equipment has only become more complex and techs that can service these products are specifically trained for it. To everyone else in the electronics repair business it's not servicable. That limits service to a handful of independent small businesses (often just one man shops), occasionally the dealers (though most contract out service work) or the manufacturer's facilities in NA or their own factories overseas. 

Not all of us can repair our own equipment, but sometimes it is possible to dive in and fix an amplifier, as I did with the Acom 1500. I saved a lot of money doing this. All the manufacturer offered in response to my query about the problem was to try a new lamp (tube). The lesson is not to rely on the manufacturer to be helpful, especially years afterward. Companies change and small companies can change very quickly. There are no certified or competent Acom tube amp service centres in Canada.

DX Engineering recently partnered with a reputable service tech to take on their warranty repairs for Canadian customers (tube amps excluded). I don't know how well that will work in practice since the PGXL is a little out of the ordinary. I didn't inquire and I hope not to find out. All of my personal acquaintances that own this amplifier haven't needed service. If it is needed it would indeed be a benefit to have it done in-country.

Shipping and insuring a fragile, heavy and expensive product for service is to be avoided when possible. For modern transceivers and amplifiers it may be unavoidable. Shipping within Canada is not as economical as it once was and shipping to the US costs more, and involves customs paperwork to waive fees each time the product crosses the border. It is only really practical to hand carry it across the border for shipping to a US-based service centre, and pick it later in the same manner. Time, travel and government bureaucracy (two of them) take their toll.

I shouldn't complain considering what hams living in many countries must deal with. They have no sales or service in their country and perhaps not even on the same continent. The low demand doesn't justify it. Not only is it very expensive and risky to import these products, you pay dearly for shipping both ways for service. Some have noted that it can be more economical to buy another rather than repair! Yes, that's extreme, but it really happens.

Next steps

My plans for CQ WW SSB are proceeding poorly. Operators have had to cancel due to life events and most within easy driving distance are busy that weekend or strongly prefer CW over SSB contests. The latter I understand since I feel the same, but a phone contest can be a lot of fun in a group. 

It may be that the PGXL won't get its intended workout in CQ WW SSB. We'll see. In the meantime I still need to properly configure it for my equipment and choose its final position on or under the operating desk. For the next while it'll be on top where I can easily access the connections on the rear panel.

A complete review of the amp will wait until I have more experience with it. So far, so good. In the meantime I need to get back to antenna work, if the birds let me! The work must get done whether I operate the contest or not.

Beverage Remote Switch Repair (Again!)

Since earlier this spring I experienced intermittent functioning of the Beverages. With the 160 meter winter season winding down the problem wasn't high on my priority list. In September the problem worsened to the point that the Beverages were unusable. The top band season has now begun so it was time to deal with it.

This is not the first time I've had trouble with the Beverage remote switch which sits on the edge of a hay field not far from the "head ends" of the 3 reversible Beverages (6 directions). When the hay is high and the weather is warm the ticks are on the hunt. In any case the radials on the big shunt-fed tower are absent during the growing season to clear the ground for my neighbour's farm equipment. Radials and farming don't mix!

In early October I went out to the switch to troubleshoot. I had already determined that the long run of RG6 out to the field was fine. It is important to sectionalize a system and test each component if you hope to isolate and identify the cause of a fault. I next inspected the F connectors on the RG6 to each Beverage and tested them. The analyzer confirmed that the Beverages were all fine -- exclusive of damage due to summer growth and other damage. That's a different problem that I am dealing with in parallel to this one.

The last remedy I tried is one that should be approached with caution. Relay contacts can develop high resistance over time if they are not periodically wetted. Wetting means switching and conducting a modest current to break the thin layer of oxidation or contamination that builds over time. The small signal from a receive antenna is insufficient to wet the contacts.

The Omron G5V relays are good in this application but are not impervious to contact corrosion. Due to the design of the switch the DC reversing current can't wet the contact because the DC is injected at the relay outputs (the selected Beverage via a bias-T). Wetting of the relays requires RF. I moved the transmission line from the rig's receive antenna port to the main antenna port and transmitted a signal. 

Use only low power for the wetting attempt since the receive antenna electronics can't handle 100 watts. I gradually increased power to 10 watts while manually switching the Beverage selection. The problem persisted so that was unlikely to be the problem.

The picture above right (taken after the switch was moved indoors) shows how I most recently tried to keep insects out by taping shut the weep holes. The tape over the one on the right had been eaten through; ants always find a way. I tore it off before I took the picture. I prepared to find insect damage, again. 

Having localized the fault to the switch itself I opened its enclosure. It didn't look good at first glance. There is clear evidence of corrosion and insect activity. As we'll see in a moment it was worse than what could be seen with just the lid removed. 

I disconnected all the cables and brought the switch indoors for a closer inspection. When I disassembled it what I found was worse than I expected. We all make mistakes and hopefully you will learn from mine. I am not shy about exposing my failures in the blog since that is how we (me and my readers) learn.

This is what I saw when I turned the PCB over.

What a mess! Compare these pictures to what the switch looked like when I rebuilt it after a lightning strike two years ago. Can you spot the construction choice I made that led to the failure? Despite how ugly it looked, I took a few minutes to seat and reseat the relays in their sockets. That also didn't help. It was time to deal with the messy interior. 

Since the small protoboard has no mounting holes I needed something to insulate it from the aluminum enclosure. I looked around the table where I was working and saw a thin piece of cardboard that was exactly the right size. I knew that it was not a great decision but used it anyway since I was in a hurry to move on to other projects on my priority list. Insects and moisture decomposed the cardboard to it original components: plant fibre (tree pulp) plus a chemical soup.

I scrubbed the PCB clean, including using a wire to push out debris that clogged many of the pad holes. All copper pads and wires were corroded, and some pads were entirely missing; soldered pads survived. Tinned wires and component leads were fine. The stranded copper wires (salvaged from an old Cat5 cable) to the F connectors snapped off the PCB since there was little metal left for them to be structurally sound. As it turned out that was the proximate cause of the failure: intermittent or entirely disrupted continuity through those wires to the chassis F connectors for the 3 Beverages. 

The solid Cat5 wires on the leftmost connector were fine. Stranded wire corrodes faster since they have more surface area. For comparison, the tinned stranded wires to the barrier strip, though coated in insect debris were in good condition.

Many commercial products intended for outdoor use have a sprayed on dielectric coating on the underside of PCBs to prevent corrosion. As mentioned, tinned wires are preferred. It is not surprising that many electronic components use tinned leads.

After cleaning the board and sanding away stains on the enclosure I soldered tinned wires from the PCB to the Beverage connectors. With that done I proceeded to test the switch. It worked perfectly.

The Beverages switched, reversing current flowed and the impedance was per the original design. I was ready to put it back together and move on to the next item on my long to-do list.

Rather than repeat my earlier mistakes and oversights, I made he following changes during the rebuild:

• Tinned wire for the leads to the F connectors
• Silicone sealant on all the weep holes and around the (replaced) fibre rimmed washers on the transmission line connector since they degraded in the weather and needed moisture protection
• Thick teflon (PTFE) insulation under the PCB, replacing the cardboard I foolishly used last time
• GDT added for lightning protection on the control leads and each of the incoming Beverage connectors; these are complementary to the GDT in each Beverage head end

Aside from one cold solder joint it worked as it should. It has now been reinstalled and all is well. I can listen to activity on 160 meters even though my transmit capability is poor until I redeploy the radials on the shunt-fed tower. That has to wait a little longer to avoid tripping hazards until work on the HF yagis is done. The northeast-southwest Beverage still needs repair when I can safely enter the bush. The other two Beverages have already been repaired, other than needing to clear the bush after the ground has frozen.

With more time I would have made other changes to the remote Beverage switch. One is to put it into a larger enclosure. It's difficult to work on since the fit is tight. Also the layout of components is not ideal due to the limited space. 

Another change would be to use a plastic enclosure. There really isn't that much risk of coupling among the Beverages without a surrounding metal cage and plastic is both easier to work with and removes the need for isolating the transmission line connector from the metal enclosure with those flimsy fibre insulators. When the switch was first built I chose the enclosure material based on what seemed sensible at the time.

In closing I'll note that my Beverage articles are among the least popular on the blog. I write about the work I do on my own station, including my equipment and operating preferences, not what I think might be popular. Few hams have the land for Beverages and large top band antennas, which likely explains the low interest. Nevertheless the lessons learned can be applied to any antenna project. That, at least, makes writing these articles worthwhile.

Priorities

The typical POTA/SOTA activist has priorities very different from mine. In their case, they need a small, compact station that is easily transported, set up, torn down and packed away. The rig is often QRP and the antennas simple. It may be a telescopic vertical, mag loop or an EFHW. They arrive at their activation site (hiking or driving in), look around for supports and then decide what antenna to deploy from the options they packed.

Those are priorities quite foreign to those of us that build large fixed stations. Indeed, my priorities are almost the exact opposite. That is the subject of this article: priorities. What do I focus on first, second and last? When my wish list is long (and growing) what do I tackle first? 

There is also the painful fact that building and maintaining a large station is a lot of work. I spend less time on the air than many hams with small stations, including the POTA/SOTA operators I alluded to. That's okay since I enjoy station work, so much so that I am happy to work on the station while guest operators have fun in the shack.

Summer is a slow time for me since the hay is growing in the tower fields, 6 meters monopolizes my attention and the warm weather entices me to engage in non-ham activities. All of that is now over. The bugs, which have been unusually fierce lately, are finally dying off as the nighttime temperatures dip close to the freezing point. In other words, this is primetime for antenna and tower work.

There is much to be done and only a limited time to get it done. CQ WW SSB is only a month away, and many of the year's major contests follow in quick succession. There are few non-contest weekends. The time has come to set priorities. No matter how ambitious I might be there will always be jobs that can't fit into the schedule and must be deferred to later, perhaps even next year or the year after.

In no particular order, this is my to-do list for the next one or two months:

• Remove the south-pointing TH6 and replace it with the new 3-element 20 meter yagi
• Install, test and tune the new (almost complete) 3-element 15 meter yagi
• Update the antenna switching system to accommodate the new yagis, involving cables and software changes, and new auxiliary switches to conserve ports on the 2 × 8 switch (all ports are occupied)
• Rebuild the 80 meter 3-element vertical yagi by taking down the central tower, building it back again higher and stronger (see picture above) -- the new guy anchors and concrete element pads are already in place
• Redesign the 80 meter 3-element vertical yagi for improved performance, then add yagi operation on the SSB band segment where it is only usable as an omni-directional vertical at present
• Repair the summertime damage to the Beverage receive antennas once I can safely enter the bush
• Complete the new antenna selection software
• Raise the XM240 to the 20-15 tower to join the new 15 meter yagi pointing south
• A new trench for at least two runs of Heliax to the 20-15 tower for the new antennas
• Purchase and install a new solid state HF amplifier
• Inspect all towers and antennas, and make repairs as necessary (done annually)
• Deploy the 16 radials for the 160 meter shunt-fed tower (also done annually)

That's just my station. I am also feverishly fitting in tower work for friends' stations. I keep busy! And that's just my ham radio life. With so much to do and so little time, setting priorities is critical. Despite not being the best or more prolific operator around, I want to do the best that I can with what I can have and can build. I make a list, arrange it by priority and dive in knowing that I'll never get it all done. That's fine: this is a fun and educational hobby, not a job.

On to my priorities. Even if yours are different from mine, the difference of perspective can be enlightening. 

#1 - Antenna Supports

Antennas needs structures to support them. While portable ops can make do with a suitable tree or a pop-up mast, the needs for a large fixed station are quite different. Height and capacity are the rule, where the only limits are money and land, or what one is willing to deal with for ongoing maintenance. Some go quite large indeed.

It is no surprise that when I first moved to this QTH, even while I was still living in the big city, that I put a shovel in the ground to build the foundation for my first tower. While that was going on I had already starting working on the first of my large guyed towers. 

In the following years more towers were raised. I can put up more but I've reached my personal objectives and I don't need or want the burden of maintaining even more towers. I fit my antennas onto the existing supports as well as I can, and antennas that don't fit don't happen.

#2 - Antennas

In a sense, antennas are the real top priority. But without supports they're useless. Thus they fall into second place. The support is paramount since if you have a tower even a simple wire antenna will perform well. A yagi close to the ground does worse. Once the supports are in place -- towers, buildings, trees or whatever -- your antenna dreams can fly.

High is good but strong is better. You want your antenna to last so the supports must be up to the loads placed on them. Assuming the supports are suitable you should utilize them to the maximum. That requires careful planning. You must have a clear idea of your objectives and understand the pros and cons of various antennas. Myths and misconceptions abound in the amateur community and you must assess antennas using facts and analysis, not the glib opinions that sadly abound.

Whether it's DX, contests, grids, rag chewing or another interest determine which antennas are best, limited only by your supports, budget, regulations and social pressures such as from your family. Within those constraints you want antennas that accomplish your objectives to the maximum.

#3 - Reaching the antennas

Transmission lines are not a minor afterthought as they are in many stations. With tall towers out in the fields every run is long, most in excess of 100 meters. They come down the tower, buried underground and then switched to the coax runs into the house and shack.

It is helpful to have friends in the business, especially those that regularly tear down old commercial tower systems. I am especially fortunate to have a friend like that who can provide me with lots of used and NOS Heliax. Most of it is LDF5 or the newer AVA5. Used connectors are also available and most of them can be reused. I won't mention what I pay but they are very affordable.

I have thousands of feet of Heliax deployed across my station, at least, if not more, than the total radial wire length on my 80 and 160 meter verticals. The new price of AVA5-50 is tracking the rising cost of copper and is now in the vicinity of CDN$7 per foot, or about $25 per meter when purchased on large reels. It will only become more dear as time goes on. Not many hams can afford that.

In the picture is some of the Heliax that I have in stock. There is a lot more out of the frame, from LDF4 to AVA7. More will be buried this fall and some is destined for friends' projects. I am pretty well set for life. I acquire LMR400, RG213 and other coax as needed for jumpers, short runs, chokes (CMC) and phasing lines. Most of that has to be bought new. Used braided coax usually means inheriting somebody else's problem.

Switching goes hand in with a multiplicity of transmission lines and antennas. What I need is more than the typical in-shack manual switch or automated 1 × N switch. 

I do all of my switching in the field with remote switches (mostly home brew) and endless quantities of Cat5 (8 conductor) control lines. Antenna selection is automatic by band and operator selectable by mouse click.

Keeping good records and tagging cables saves many headaches when troubleshooting and install new antennas and switches. I am fortunate to have had few problems with the many switches and kilometers of cable in my station.

#4 - Equipment

Well down the list is the item that is at the top of most hams' priorities: shack equipment. This includes transceivers, amplifiers, keyers, PCs, software applications and other operating aids. My reasoning is simple: a poor rig, even ancient or fully manual, paired with a good antenna is far superior to a poor antenna connected to a top of the line rig.

Yet eye candy regularly attracts many, while the antennas and supports come second or third. I can understand the reason because for most hams putting up towers and big antennas is difficult to impossible. A well laid out shack with state-of-the-art equipment is beautiful to behold. I don't value prettiness very much, and with few restrictions on towers and antennas I prioritize the latter.

As the antenna systems mature I am paying more attention to the equipment. The transceivers that I own are becoming more modern and I plan to have modern solid state amps before the year is done. More software changes are in the pipeline to simplify antenna selection and rotator control. You can see a few of these items on my to-do list above. 

#5 - Cleanliness

This is a broad topic that I struggled to give a single label. What I am trying to convey is that, for me, function takes priority over form. That is, make it work and only then make it "clean". Let me give a few examples.

Look at the picture immediately above. Does that look clean? Of course not! But it functions very well. The base of the Trylon tower near the house is where I put the 2 × 8 switch, auxiliary switches to conserve ports, Heliax terminations and manually crimped cross-connections between control cables. I have to refer to my extensive notes before touching any of it so that I don't accidentally cause trouble when making changes!

Could I clean it up? Certainly. But it works so why mess with it. Spending hours to clean it up would make it pretty yet change little. As infrequently as I need to make changes (adding antennas, transmission lines, switching) it is sufficiently navigable. Function over form.

It is frequently hammered into our heads that BPF (band pass filters) and CMC (common mode chokes) are vital station components (SO2R and multi-op contesting) that must be used or switched for every antenna when it goes up. No, not really. Yes, these devices will clean reception (less QRN & QRM, and inter-station interaction) but are not absolutely necessary. I've operated SO2R without BPF and CMC, and although there are problems those can usually be worked around.

CMC are installed as necessary, but always when a big antenna goes up and the feed point is inaccessible from the tower or it is part of the phasing lines for stacked yagis. BPF were eventually built and installed in my station, which makes for happier operators. High power BPF after the amplifiers would be even better but from experience they are not critical in my station. Maybe I'll increase their priority when I complete the migration to solid state amps.

For operator selection of antennas, the first system was manual and the second was a single software UI (user interface). The next version will give each operator their own UI and eventually touch control. The many rotators are yet to be software controlled which means they must be within the reach of both operators for direction readout and rotation. For now it works; function came first with cleanliness to follow, eventually. 

The same principle applies to my gradual migration from relatively inexpensive manually tuned amps to broadband solid state amps. Since nobody on the other side of the QSO cares how the amps are tuned they don't really impact results. That is, other than the few seconds needed to re-tune after band and (sometimes) antenna changes.

My priorities this season...

In light of my priorities and the long to-do list presented above, I have a plan for how to attack it. The jobs that will get done are ones I deem highest priority or reasonably easy to fit into the available time. Several can be done indoors when the weather turns too cold for most outdoor work.

There is also quite a lot of maintenance to be accomplished, which is a never ending item on my list. For example, an accident with a tractor was unkind to one of the guy anchors for the 80 meter yagi rebuild. If all goes well the antenna rebuild will be done by CQ WW SSB.

The new 15 meter yagi will go up shortly. Its side mount bracket is already installed on the tower. The auxiliary switch for it is being built. It won't require any of the new Heliax. Then the TH6 will be retired and replaced by the new 20 meter yagi. It, too, requires no new Heliax, and both it and the 15 meter yagi should be ready in time for CQ WW SSB.

A new solid state amp hasn't been ordered but once done it'll be here within days. I have been slow to choose from among several alternatives. My top choice has several negative points that I would like to address being spending the money. An expense of this amount justifies careful thought. There is no amp that is perfect for my needs, and none of the big ones are inexpensive. 

...and beyond

Although I don't want another tower I am contemplating one anyway. It would be located far from the others. Its height would be modest to support a few small yagis for 40 through 10 meters. Perhaps the TH6 and XM240. Its intended use is for an in-band station that would be nice to have during multi-op contests. 

The antennas need to be far enough away and suitably oriented to minimize interference with another kilowatt station on the same band. I've operated an in-band station elsewhere, which can be a lot of fun and add significantly to the score. A further benefit is that it keeps more operators operating rather than impatiently waiting for a vacant seat. Well, it's just a dream at this point.

There are other projects being contemplated. Nothing too big or challenging, just enough to make a difference and continue the journey I began almost 10 years ago. How time flies. A retrospective of the past decade is planned when the anniversary arrives in the not too distant future. It'll be interesting to review how far I've come before turning my attention to 2027 and beyond.

3-element 15 Meter Yagi

The 3-element 20 meter yagi that I recently built now has a sibling for 15 meters. As previously related, both are meant to replace the TH6 pointing south. The tower work is planned for completion before CQ WW SSB at the end of October.

This antenna is not simply a scaled version of the 20 meter antenna. There are differences that are worth a discussion. Nothing was purchased for this antenna since all parts come from my stock, just like for the 20 meter yagi. Other than ⅝" and ½" tubes, all of the aluminum tubes and plates come from discarded yagis that are decades old. 

Limiting myself to what I had in stock imposed constraints on the mechanical design, which in turn affected the electrical design. There are asymmetries that made it difficult to use NEC2 for the model, which I prefer to NEC5 for conventional yagis. With some work I was able to achieve good agreement between both calculating engines for the gain and pattern, but not quite for the impedance. The last isn't surprising and is not critical since the matching network at the feed point is adjustable. As for the 20 meter yagi, the model uses a hairpin (beta) match since it easier to model than the gamma match that is actually being used.

Element taper

From my stock I selected 3 centre pieces that consist of a 1-⅛" tube pierced by a 1" tube. The faded marks were there originally and indicate that at least two of these came from a 15 meter yagi. One of the centre sections is longer so I used it for the reflector, the longest element. Dimples rather than hardware prevent movement of the 1" within the larger one. That's unusual but I've seen it used several times in very old antennas. There were no defects to speak of so I left them as is. 

The ends of the 1" tubes came with slits, stainless hose clamps and self-tapping screws to secure the nested ⅞" tube. I removed the screws, drilled through that small hole and out the other side of the tube for #8 stainless screws and nylocs. I reused the hose clamps rather than replace them with #8 hardware.

The ¾" tubes were already secured to the ⅞" tubes with the metal strapping described in the construction article for the 20 meter yagi. I cut those off for the DE since the combined ¾" & ⅞" sections were of unequal length. Swapping tubes resulted is nearly equal length sections. This kept the DE centre of gravity at element centre (over the boom) and enabled EZNEC's SDC (stepped diameter correction) in the NEC2 engine which requires element symmetry. NEC5 doesn't have this sensitivity, requiring neither symmetry nor SDC.

For the tips, a 1' length of new ⅝" tube is inserted into the end of the ¾" tube. The tip are ½" tubes. The first picture in this article shows the assembled elements without the tips. I avoided adding tips until the design met my objectives. The equivalent diameter of the element-to-boom clamps is 2.7" using the W6NL equation for a tube resting on a plate. The boom and hardware have a effect small enough to be ignored during design and construction.

Unlike for the 20 meter yagi the elements are not isolated from the boom. There are no destructive interactions with the antennas near where I plan to place it on the tower.

The final taper schedule of the half elements is as follows, skipping over the element-to-boom clamps. Dimensions are distance from element centre, not the lengths of the tubes:

• 1-⅛": 6" (D and DE), 9"(R)
• 1": 24.5" (D), 25 (DE), 26" (R)
• ⅞": 64.5" (D), 76.5" and 65" (DE), 77.5" (R)
• ¾": 104.5" (D), 116.5" (DE), 128.9" (R)
• ⅝": 113.5" (D), 125.5" (DE), 138" (R)
• ½": 127.5" (D), 130.1" (DE), 146.4" (R)

This is obviously not what an antenna builder would choose when using new tubes. I simply worked with what I had. Aluminum isn't cheap. The lengths of the ½" tips are for my final design, which is discussed in the next section. There were many iterations to get what I wanted.

Design and model

As you may recall from the 3-element 20 meter yagi design, I tried to keep the "spread" between the director and reflector as small as possible to maximize gain. That is, the square root of the ratio of their self-resonant frequencies. High gain increases antenna Q so there is a trade off with the SWR bandwidth. To keep solid state amplifiers happy the SWR should be below 2 across the band, and preferably better than 1.5.

To achieve this across the 350 kHz of the 20 meter band for the selected boom length and element taper schedule I eventually had to settle on a spread of 8%; that is, the director and reflector self-resonant frequencies are approximately 8% above and below the design centre frequency, respectively (see above). It is possible to do better on 15 meters since, although the band is 450 kHz wide, there is a smaller proportionate range due to the higher frequency. 450 kHz at 21 MHz is 2% while 350 kHz at 14 MHz is 2.5%. That seemingly smaller bandwidth permits a tighter spread, and thus higher gain, for the same SWR bandwidth.

After iterations with a 15 mm constant diameter wires on a 15.5' (4.7 m) boom it was possible to achieve the SWR bandwidth objective for a 7% spread. The raw boom length of 16' is proportional to the 24' boom on 20 meters, with several inches on each side reserved for the width of the element-to-boom clamps. The SWR bandwidth was about the same for a model with the above element taper schedule using NEC5. That's the plot shown here, using a beta match and a 7% spread.

Then I had a boom problem. Although I have lots of 2" boom material, the tubes were all 9' or longer. I hate waste so I didn't want to cut any of them. Since 16' isn't very long I decided to make an 18' boom. That increases the boom from 0.33λ to 0.37λ, measured from reflector to director. Since gain is in proportion to boom length the gain also increases. It isn't a lot but every fraction of a decibel counts, in this case from 0.2 to 0.3 db.

After tuning the elements in the model the SWR bandwidth was preserved and the gain increased across the 15 meter band. The only downside is less F/B, losing between 3 and 5 db. That did not surprise me since, unlike gain, F/B tends to have a cyclical pattern as the boom lengthens. For those who cherish F/B it is important to choose boom length with care. 

F/B rarely concerns me as a contester since I want to work stations off the back of the beam. Less F/B means that more stations hear me. It's to my advantage. For an occasionally used yagi fixed south to work contest multipliers it's even less of a concern. Look at a map of my location and you'll see that there is little likelihood of QRM off the back (north).

For the final design the placement of the elements on the boom, with the reflector position at 0, the DE is at 93" (236 cm) and the director at 210" (533 cm). Moving the DE a few inches could improve the pattern or gain, but only slightly. Therefore I didn't both to optimize further. Had this been a more important antenna I would have taken the time.

The SWR has barely changed with the longer boom, with a just a small increase at 21.45 MHz. This plot was done with NEC2 and EZNEC's SDC after making the elements symmetric in the model. The NEC5 plot is the same but due to the differences in the engines the modelled impedances are not quite equal. For the purpose of the plot it wasn't worthwhile to adjust the model's beta match to compensate. The small impedance difference is not important since the range of the gamma match can accommodate it. 

NEC5 typically needs many more segments for the impedance to converge to its true value. I did not test to determine whether that was the cause of the difference in this model.

My final caution with modelling and building yagis is that you should trust the tools. I am frequently amazed (and amused) by how many hams like to denigrate modelling software and would rather stumble along with their antenna projects, trying to convince themselves (and others) how great their antennas are. It's nonsense. 

NEC5 in particular and NEC2 when coupled with SDC are remarkably accurate. Believe the results and build your yagi exactly as in the model. Every fraction of inch makes a difference, even at HF. Don't guess! Measure and cut per the model, and when you can't (as for some of the tubes in this model), enter the model data exactly to the tube measurements. For HF yagis each tube should match the model to within ¼". At the very least ensure that the half element lengths are within that tolerance.

For example, my initial design had 6" lengths of ⅝" (3" nested and 3" projecting). That was to conserve my dwindling stock of ⅝" × 0.058" tubes. I later went with 12" lengths (9" projecting) and reduced the ½" tips by the same amount. The frequency shift of the yagi was significant. You might not notice it in practice since gain is very difficult to measure. But it makes a difference so you should strive to get it right. All the element half lengths had to change by about ½" (1" total per element) to return the model to where I wanted it.

Assembly and various supports

Unlike the 3-element 20 meter yagi, the boom is shorter and lighter and therefore amenable to a simpler solution for joining the two 9' section of 2" × 1/16" tubes. Digging through my junk box I found a spare Hy-Gain boom coupler. Although the aluminum alloy is thin wall it has served well on their large line of HF yagis over many decades. I don't know where this one came from.

The coupler is 10" (25 cm) long and is designed for 2" tubes. I've used these Hy-Gain clamps in the past on 1.9" OD pipes so it can handle a small range of sizes, provided both tubes are the same diameter. There are 2 through bolts and 4 clamp bolts, all sized for 5/16" hardware. The other 4 holes are for Hy-Gain two-piece mast clamp. I didn't have one of those handy so I made a mating plate from 3/16" steel.

The 4 inner holes for the mast clamp are arranged in a 3" square. The through-holes for the tubes are 4" apart and centered on the square. I drilled ⅝" holes for the projecting through-bolts. I could have made cutouts around those holes but drilling holes is easier and leaves a little material on the sides for added strength. The plate could be made a little wider than the 5" seen here. The antenna is small and light enough that I deemed this to be sufficient. 

The reason that I used steel was that I was running low on aluminum plate of suitable size and thickness. Steel is cheap and strong so I picked up a 6" × 3/16" remnant I saw while waiting for other steel stock to be cut to size for other projects. The downsides are that it is more difficult to machine than aluminum and it requires a rust protection coating. It's routine for me from my long time building towers and antennas. I plan to make a similar plate for the recently completed 20 meter yagi.

The holes for the galvanized saddle clamps are also 5/16". The 6" height leaves ⅞" on top and bottom, to leave enough space between the mast clamps and the Hy-Gain boom clamp, which is 4-½" high. The holes for the u-bolts were set after selecting the saddle clamps. Be careful because there is no reliable standard for u-bolts and saddle clamps for the same size tubes or pipes. Don't guess, measure.

When making custom antenna hardware it is important to carefully consider the placement of all hardware before cutting the metal and drilling the holes. It helps to be able to think in 3-dimensions. Loosely lay all the parts per the design to find any conflicts. You could end up saving a lot of time and material!

Which direction you orient the bolts can matter. I placed the heads of all the 5/16" bolts on the plate side of the assembly to avoid interference with the clamps. Also, lock washers should always be on a flat surface, not a round one. If you must place the nut on a round surface it is better to use a nyloc or jam nut. Most of the bolts are stainless for easier maintenance should it be required.

The motley selection of element-to-boom clamps are due to what I had available in my junk box. I couldn't be bothered to go to the trouble of making better clamps for this lightweight yagi.

The u-bolts for the director and DE (top two in the picture) use formed threaded rod. I've seen this construction method on antennas made 40 or more years ago. That's useful for custom sizing but otherwise a really bad idea. Tempered steel is weakened by bending and milder steel that can be formed in this fashion may not be of sufficient tensile strength. It is also difficult to get a consistent radius of curvature. But, again, the antenna is small and they were in my junk box so I used them. For the longer reflector I selected an element clamp with conventional galvanized and plated saddle clamps.

The gamma match comes from an ancient 15 meter yagi so it has suitable dimensions. The 7/16" gamma rod is 5" from the DE (centre-to-centre). I cut the insulated support bar from an ABS pipe. The coax connector is on a 1" aluminum bar, the wire from which is bonded to a short piece of the same ABS. The RG213 centre conductor for the gamma capacitor is not present in the picture. It will be cut to size during testing and tuning then soldered to the wire and sealed. The 3 u-bolts on the DE are from my stock of stainless hardware.

It looks nice when assembled in the hay field. Its measured weight is 27 lb (12 kg). The boom truss will be dacron rope to be tensioned by hand rather than turnbuckles. I prefer to avoid steel truss cables for side mounted yagis to avoid unpredictable resonances of the total system that might destructively interact with nearby rotatable yagis.

Next steps

There is as yet no tower bracket for this antenna. That is nearing completion in my workshop. Since the testing of the 3-element 20 meter yagi went so well and this one is similar I skipped doing a separate test and tuning of the yagi. I'll install the new bracket, tram the yagi onto it and then test and tune it. The gamma match is easily accessed from the tower since the DE on a 3-element yagi is near the centre of the antenna.

There will also be a need for antenna switching since there are no spare ports on the 2 × 8 switch. An auxiliary switch is being made to switch the transmission line for the 15 meter stack to the 3-element south yagi. Antennas for the same band to not need to be simultaneously accessible. I considered putting the relay and port on the 15 meter stack switch but it is already crowded inside. The switch will be installed on the tower close to the upper end of the Heliax transmission line.

The new yagi will be raised by early October, and then the switch built and installed. I will have more to say about these when the job is done.