W5WVO 6m Beam Project

W5WVO clone construction so far.

I wrote earlier on my purchase at the Dalton, GA Hamfest of the 6m Mystery Beam. It clearly formed some kind of antenna, given the lengths of the elements. But I had no clue how those elements were intended to be positioned on the boom -- and even if I did, I had no idea what kind of performance to expect.

Course of Action

Unsure of what to do, I asked the folks on he SEDXC mail reflector. Joe Subich, W4TV suggested that I use the components to implement the W5WVO modification of the A50-5S, or perhaps re-create one of YU7EF's five element designs for a 4.5m boom or 4.15m boom. 

Choosing between these options was difficult. What I had wasn't a A50-5S, so the W5WVO medication wasn't straightforward. And the YU7EF designed were even further afield from my starting point.

I decided to adapt my tubing collection to W5WVO's design. 

My elements were too short, they'd need to be extended. But, it isn't as simple as just matching the length W5WVO specified -- the taper schedule is different. 

The A50-5S and the W5WVO designs use 48" of 3/4" tubing in the center extended with 5/8" tubing to the element length. My tubing is 3/4" the entire way. I'd need 5/8" extensions, but how long?

Answering that question required modeling.

Modeling a Solution

As a Mac user, I use CocoaNEC with the NEC 2 engine. It's pretty sophisticated, actually, but getting good results requires using the NC modeling language, which can be a bit tedious. 

My first model was W5WVO's design using the normal taper schedule - inner 24" of each half element are 3/4" with the rest being 5/8". Results were very similar to, but not exactly the same as W5WVO's article. (Part of the reason is W5WVO used NEC 4 engine) But what I had was close enough.

Second model used the 3/4" element lengths I had, spaced according to the W5WVO design. The results were akin to the W5WVO, but with significantly worse F/B.

Third model used the same 3/4" element lengths, with 5/8" extensions on the tips of each element. Because of the different taper schedule, I experimented using a different percentage of the W5WVO dimensions. Lo and behold, at 80% extension length, I modeled something very, very close to the W5WVO design. 

Reflector with
5/8" extension.

The extensions needed on each end are short:

• Reflector - 2.5"
• Driven Element - 0.75"
• Director 1 - 1.75"
• Director 2 - 1.375"
• Director 3 - 0.25"

I added about 3/4" for overlap inside the 3/4" tubing. I secured the extensions using 1/8" Cherry pulled rivets. These aren't ordinary "pop" rivets. Ordinary pop rivets are just a hollow aluminum tube. These leave a steel mandrel filling the tube -- a solid, structural connection.

Building

Extensions on each element.

First step involved cutting the extensions and riveting to each element. I used two rivets on opposite sides. On the D3 element, with the very smallest of extensions, I ended up with one rivet because I broke my #30 drill bit. 

Second step would be to hang the elements on a boom. Oh, wait, I need a boom!

The parts I bought at the Hamfest had three segments of 1" Aluminum pipe which was reinforced by a 13 foot piece 3/4" pipe. None of this fit well together. And the diameter was somewhat small for a 20 foot boom.

I had a 7 foot piece of 1-1/2" tubing I replaced on a Cushcraft A3S. I also had a 12 foot piece of 1-1/2" tubing. Together, they would be 19 feet. The last 10" of the 7 foot tubing had a crack, so I cut that part off, and used a  1 foot 1-5/8" tubing section to join the two together. My only hesitation was that the 12 foot piece was only 0.035" wall (whereas the others are 0.058"). I was worried it might not be strong enough. I figured it was worth a try, perhaps aided by a supporting truss.

I also had to figure out a boom-to-mast plate. I was fortunate to have one in the junk box, along with U-bolts that would work.

Mapping the elements onto the boom was a little tricky. The U-bolts just barely fit over the 1-1/2" boom, but they could not go over the 1-5/8" joiner. I had to move the reflector 8" away from the end of the boom so that Director 2 did not fall on the joiner. 

I managed to get all the elements positioned on the boom. Definitely looks like an antenna now.

Next step will be to figure out how to feed this beast with a gamma match.

Hamfest Special - Mystery 6m Beam

Back in July 2021, I asked members of the SEDXC reflector how best to work Europeans on 6m, one important bit of advice was to use an antenna with more gain than my Cushcraft A50-3S. Three elements just won't cut it on marginal paths. The suggestion was to use a beam with five or more elements. 

Such antennas are several hundred dollars new. The A50-3S was used from a local club for $80. Yes, I'm cheap, but it has served me well. Since then, I've been looking for a reasonable, used antenna. I'm even willing to do some minor repairs.

As I was leaving the Dalton, GA hamfest at the end of February, I stopped by a tailgate area where a guy had a trailer load of stuff. I could see a Cushcraft tribander, a Hy-Gain tribander, house brackets, guy brackets, feed lines, a gin pole and other stuff. I wondered if he might have something for 6m. So I asked.

The owner wasn't present, so his kid called him on a digital walkie-talkie. He said he had a 5-element Cushcraft 6m beam. By the time he made it back to the trailer, we pulled it out, and he changed his tune, he said it was a 6-element Hy-Gain beam. You could see the gamma feed on the driven element. 

Sounded great to me. I negotiated him down to 63% of his asking price, and walked away with the antenna bundle for $125. Sweet.

Getting home, before  I took the antenna off the truck, I went looking for Hy-Gain six-element 6m antennas. I found manuals for models 66B and VB-66DX. They are very similar. The VB-66DX appears to be a hardware-update of the 66B design. These antennas are also fed with a beta-match, not a gamma-match. What I bought is not a Hy-Gain antenna.

Taking the antenna off the truck, cutting it apart and laying the pieces out on the deck.What I found was surprising:

• 

  The components I purchased
  

  REF - 3/4" Al - 9' 9" - 117"
• DE - 3/4" Al - 9' 2" - 110" (Gamma match)
• D1 - 3/4" Al - 8' 9" - 105"
• D2 - 3/4" Al - 8' 8" - 104"
• D3 - 3/4" Al - 8' 7" - 103"
• Misc - 1/2" Al - 50" - Swaged to 5/8" last 6" (2) - Hy-Gain bracket adds 1 1/2" - 101 1/2" total
• Boom - 1 1/4" Al totalling 24 feet in three sections with 1" thicker wall inner tubing

First five elements mount with a single 1 3/4" U-bolt and saddle in the center. The Misc segments could mount in a single Hy-Gain bracket, giving a total element length of 101 1/2" -- which might be a forth director.

Gamma match is a total of 16" 1/2", most of which is a 1/4" Aluminum rod. The shorting bar is at 14 1/2". The first 1 1/2" is a 1/2" Al tube flattened at one end for a screw. The open end hid a disc ceramic capacitor that sadly I broke in transit. Looks like a 3-6 kV capacitor, value unknown.

The boom is a piece of work. There are three 1" Al pipe sections: 75 3/4", 144", 68". The 68" section has a 156" piece of 3/4"Al pipe with a ticker wall as reinforcement. It is mounted asymmetrically, so more of the end extends into the 144" piece than the 75 3/4" piece. There is no boom to mast bracket.

I'll note that the boom is aluminum pipe. Not tubing. It's designed to carry liquids, not be structural.

Clearly, this is not the parts to a Hy-Gain nor a Cushcraft 6m beam. First off, no commercial 6m beam ships with single-tubing size elements. They all use a taper schedule. There are two good reasons for this. 1) It makes the antenna adjustable. 2) they can ship sections shorter than 7 feet, which allows the package to go UPS, 

These parts are a collection different ideas. The U-bolt mounting is Cushcraft-style, but the boom size is too small for a Cushcraft. The boom is 24 feet long, but it is clearly not a Hy-Gain. The boom is way too small, since Hy-Gain used a 2" boom. Plus, it apparently had a truss (now broken), probably because the    for the 24 foot length.

What I appear to have is a collection of parts used to cobble together a poor imitation of something like the Hy-Gain 66B / VB-66DX. Not at all what the guy at the hamfest told me.

There's plenty here to put together a solid five element beam on a 12 to 18 foot boom. The elements are already cut. The hard question is how far should they be spaced? Once I know what the right spacing is, I would then know how much boom I need. 

The broken gamma match is annoying, but fixable. Once I know where to place the elements....

This project is going to take some work.

The Challenge of a New QTH

A decade ago, my wife and I spent four years in Floyd County in one of her church postings. We loved the area, and imagined we'd retire there.

In November we took the first step. Bought a house in Floyd County near Rome, GA. House is on the top of a small mountain - Ward Mountain, rising 300 feet above the valley floor below. From the front porch, there is a gorgeous view to the West. On a clear day we can see 35 miles to Lavender Mountain, which is practically in Alabama,

The house is a little smaller than we'd like at 2100 square feet, but there's over 11 acres of land. A small office outbuilding with one room and a tiny bathroom has become the ham shack.

We've owned the house in Gwinnett county for 30 years. Now we are transferring things to the new house. There's a lot to do. We'll sell the Gwinnett house in the next months. In the meantime, I'm focused on building up the Floyd QTH when I have the energy.

Antennas are the first order of business. I first put up an 80/40/20m Trap Dipole. It's up about 12m in the trees. I erected a 160m Inverted-L with two elevated radials. It's a bit noisy, so receiving antennas are likely needed to make the most of that. I plan for three beverage antennas. A 6m dipole barely 4m up in the trees offers me an option on that band.

I've also put together the HF4B. I've mounted it on a 19 foot pole lashed to a deck post. It needs adjustment to work well. It's OK on 10m, but 15 and 20m aren't quite right.

I'm planning to put up a tower. I'll need to take down the tower in Gwinnett first. My plan is 70 feet of Rohn 25, with the A3S/A743 on top. 35 feet below that will be an A3S, pointed at Europe. This would give me a stack toward Europe, plus coverage in other directions with the top antenna. Horizon is unobstructed in every direction except to the NorthEast, where the two additional summits of the Ward Mountain chain are. Those peaks are just 100 feet and 140 feet higher, but they are 1 km and 2 km away, respectively.

I'm already seeing good results with the 80/40/20m trap dipole. There are benefits to being on the top of a mountain. Even a simple tower should be awesome.

For 6m, I'm on the lookout for a 5-6 element beam. The Cushcraft A50-3S i've been using in Gwinnett just doesn't have enough gain to work the intercontinental paths. 

On the office building, I've already moved in an operating desk with desktop shelves, and another luncheon table that serves as a workbench. The main part of the floor is a little more than nine feet square, And almost six feet of the rest of the building is split between the tiny bathroom and the rest of the floor. The desk and workbench are a bit of a squeeze.

A wire shelving rack takes up some of the space opposite the tiny bathroom, and gives me room to store things. I don't know how I'm going to get a whole basement of ham gear into this little building.

Such is the challenge of a new QTH.

Fixing up the Cushcraft A50-3S

A50-3S standing tall and
straight next to the house.

Last year, I moved the A50-3S out of the yard and up next to the house. I used a 19 foot mast made of two pieces of EMT. While putting it up the reflector bumped against the roof and turned askew about 15 degrees. 

Never the less, it worked well. I worked a few Europeans and several South and Central American using this antenna.

Still, it needed a bit of work. A one-piece mast would be better, and I could straighten out the reflector when I swapped masts. A bead balun at the feed point wouldn't hurt either. 

So, I researched these. You would not believe what a 20 foot piece of 1 1/2" 0.058 wall aluminum tubing goes for these days. A few years ago, I purchased a 12 foot piece of 2" diameter 1/4" wall 6061-T6 tubing for my gin pole. It was about $150, which seems right for such a substantial piece of metal. 

But 20 feet of the thinner mast? They quoted me $500! If I went with the 1/4" wall, well that was manufactured with a different process -- extruded instead of rolled, so it would be $250. Ridiculous. There had to be another solution. 

I did have 20 feet of mast in two 10 foot pieces. This was from an earlier experiment. I had an old Butternut  HF4B that I had rebuilt, and was hoping to erect in Fulton County. I bought two pieces of Rigid Metal Conduit (RMC) for this purpose. 

EMT and RMC are easily found at your local Home Depot. But it isn't exactly what you would call structural. EMT is design to bend. Easily. I have had some success using it as masting for very small, light antennas. The two pieces I used on the A50-3S lasted for over eight years, plus the several years holding up a 19 element 2m boomer Yagi. RMC is more substantial, and comes with threaded couplings to connect them together. 

Two pieces of 10 foot RMC was $30 a pop, so this wasn't a cheap experiment. Even with the coupling tightened all the way down, the 20 feet of mast had a substantial wobble in the top section. I tried inserting a solid piece of HDPE. That helped, but not enough to hold up the HF4B. 

It occurred to me that this might work with the A50-3S, even with the wobble. The A50-3S is held upright by a wall bracket at the eve of the house, well above the wobbly union. I just needed the vertical support, and not so much lateral rigidity. Besides, I already had $60 invested.

First order of business was to find the doggone things. I put them away three parsonage moves ago, and had hidden them well. They were hiding in my basement. After that, I had to locate the piece of HDPE, which I found in another box. 

It all came together this week. My youngest daughter Lauren helped me to lower the existing A50-3S and mast to the ground. Off came the antenna and the feed line, and the old mast was disassembled and put away. Then I coupled the RMC together with the HDPE stiffener and taped the coupling joints against any water intrusion. With the A50-3S mounted on the new mast, the reflector was aligned with the rest of the elements. 

For a balun, I used five snap-on ferrite beads. I measured these at about 100 ohms resistive at 50 MHz. Five conveniently fit on the 9913 coax from the driven element to the mast, so that is what I used. 

A50-3S facing South East.

Swinging the new mast up into place without bashing the antenna against the house took some patience. The RMC mast is much heavier than the two pieces of EMT. Once vertical, I positioned the mast in the eve bracket and loosely connected the u-bolt clamp. Both my daughter and I lifted the assembly to the top of the railing. From there, I tightened the bracket to eliminate play, but loose enough to allow the antenna to rotate. I used a couple of extra 1/4" nuts as jam nuts so the bracket could not tighten or loosen. 

The antenna is easily Armstrong rotated from the base. Eventually, I'll mount a rotator on the top of the railing and retire my arms.

A quick SWR check showed a 1.2:1 SWR at 50.313 MHz. The antenna is pretty broad. Minimum SWR is around 50.8 MHz at 1.07:1. I suppose I could mess with the matching network to get a better match on the FT8 frequency, but the whole bottom 2 MHz of 6m is less than 1.5:1. 

The antenna is 28 feet (8.5m) off the ground with clear shots from the North clockwise to the South West. Points to the West and North West have to pass through the house roof.

I hope Es season hasn't passed me over yet. 

Tuning the A3S/A743

Adjusted A3S/A743, ready for rotator.

After adjusting the A3S/A743 on the ground and getting it back on the tower, I was very disappointed to find the SWR dips for each of 10, 15, 20 and 40m were all outside the band. They were all too low. This surprised me. When I measured the antenna with the beam facing upward, the dips were very close to the band. Now that the antenna was on the tower, it was going to be more difficult to adjust.

Rick Dougherty, NQ4I, gave me an important tip. Always measure horizontal antennas horizontally. Don't attempt to make measurements with the antenna vertical. With the antenna 6-8 feet off the ground, you can get a good sense of the measurements, knowing that the antenna will rise in frequency as it moves away from the ground. Generally by about 100-300 kHz at the 30 or 40 foot level. As you move further from the ground, the effect lessons. 

Rick knows his stuff -- he built a superstation in Griffin, GA, and has experienced this phenomena putting up dozens of antennas. 

OK, I didn't follow Rick's belated but sage advice - what should I do now? I didn't want to take the antenna off the tower again, it was a lot of trouble to get it up there in the first place. I decided I could make adjustments similar to how I added the A743 option originally - by tipping the Driven Element (DE) vertically and climbing down the tower.

On the tower adjusting
the now vertical DE.

One the first climb to make adjustments, I could already see part of the problem - some of the DE joints had slipped outward while the antenna was waiting to be installed pointed vertically. The extra weight of the A743 parts probably had something to do with this. 

Loosening the U-bolts for the DE and the support mast, the DE tipped over easily and I was able to climb down the tower and adjust. I had to make some of the adjustments somewhat blind, since I could not easily put a measuring tape against the elements. 

I ended up with the 10m traps out about 83.5" (A), the 10 and 15m traps spaced as 6" (B), and the 15 and 20m traps at 18.75" (C) -- this was the lower limit, since the tubing ends were contacting each other inside the support tube. the 40m portion I extended to about 66". These measurements are for each side of the DE.

This took two climbs, and ended up with the 10, 15 and 40m SWR curves well centered in the bands, and 20m right at the bottom of the band. This isn't perfect, but it is usable. Note I did not make any adjustments to the Reflector or Director, as they are well out of reach.

Next time I set up an A3S/A743, I think I will adjust the 10 and 15m portions to the MID-band settings, and split the MID and CW settings for 20 and 40m. That's roughly where I ended up anyway. 

I'll also consider replacing a lot of those stainless steel worm clamps. After being out in the weather for 30 years, a few of them would not tighten the way I would like. 

The A3S/A743 should be ready to go after one more climb to raise the antenna and install the rotator. I also plan to tweak the support mast a bit higher to keep water from accumulating in the 20m (TK) traps, since that's likely how they failed in the first place. 

Rotating Again!

Well, it didn't take months after all. As I wrote last month, my A3S/A743 had been stationary since December. But with the beautiful spring weather here in Georgia, I managed to get to the top of the tower and finish the installation.

It's now rotating freely, as expected. It's really good to be able to use the beam as intended, and not have it fixed roughly east.

I do wonder if the A3S/A743 needs repair, however. I'm still seeing occasional SWR shifts at 100 watts on 40 and 20m. I'll need a gin pole to take the antenna down to refurbish.

Back on the Tower Again

During my December vacation, I started a rather ambitious project on the tower. Since its installation, my A3S/A743 has been about eight inches from the very top of the mast. My intent was to put the beam at the very top of the mast, in order to give more room to stack an A50-3 under it.

It had been a while since I climbed on the tower, and any work at the very top is always nerve-wracking. As I've written before, sometimes you get up there and decide you've had enough.

Anyway, back to the December project. I conscripted my daughter Lauren to be my ground crew. I ascended the tower, removed the rotator and hung it from a couple of nylon loops off the side of the tower. Then I lowered the mast into the tower, until the A3S/A743 bracket was right at the top of the tower. The mast and antenna are somewhat heavy, weighing about 50 lbs. I relied on a pulley at the top and bottom of the tower and a haul rope to get support from my ground crew.

The tricky part of this operation was going to be moving the antenna higher on the mast. I had two options. First, I could loosen the bracket U-bolts, lift the antenna higher, then retighten. This would only take me about five hands, and I was only born with two. Second, I could loosen the bracket U-bolts, then lower the mast into the tower. While this seems easier, I had visions of the mast going too low and the antenna falling off the tower. Plus, I was afraid that we'd drop the mast and it would fall some 40-some feet into the base of the tower. And then the antenna would fall off the tower.

Plus, my daughter was having a lot of trouble getting sufficient leverage on my pull rope, which was 1/4". After being at the top of the tower a little over and hour, I decided to continue the project later.

Little did I know that it would take two months before I could get back up there!

In the intervening time, I had purchased 120 feet of 9/16" braided black poly rope. Our first order of business was to replace the existing 1/4" rope with this much more substantial lanyard. Once again with my trusty ground crew, we set out to complete the project.

With the bigger haul rope installed, I surveyed the top of the mast. I had thought that perhaps the antenna had slid down the mast in the 18 years it has been up. But a close examination of the mast showed no evidence of that. It had always been at that level.

Standing there 40-some odd feet in the air, 20 feet above the edge of my roof, I wondered if loosening the antenna would get me into a whole new world of problems. I decided at that moment I wasn't going to mount the A50-3 under the larger beam. What we needed to do was hoist the mast back and up and put the rotator back in place.

This proved to be a problem. Despite all her hauling away on the rope, Lauren was unable to raise the mast any significant distance. It was only with me grabbing the mast with two hands and pushing we were able to move it at all. I ended up locking down the mast with a couple of bolts in the tower and climbing down to solve the problem.

I had a ratcheting come-along, but hauling it up and using it on the tower was problematic. I ended up tying the come-along to a support pole, then hooking it into the haul rope via a tied loop. This would allow Lauren to use the come-along to provide lift, and I could manage things at the top of the tower.

After climbing back up, things moved a little more quickly. The come-along provided plenty of tension, but I found that I had to move the mast with my hands to get it to budge -- there's just too much friction and too much stretch in the poly rope. In a few minutes, we had the mast nearly back up into position. I had to re-position the pulley to get the last few inches to make room for the rotator.

With the mast locked down again, I hauled the rotator back into position. Thereupon I discovered two problems. First, one of the four nuts on the U-bolt that clamps the rotator to the mast was missing. In the two months on the tower, it apparently shook loose and fell off. Second, the rotator connection at the base of the rotator were loose -- one of the forked lugs had fallen off the wire and would need to be replaced.

Not having the necessary hardware at the top of the tower, I finished as much of the assembly as I could and came down the tower knowing that this project would be finished on another day. Hopefully, it won't take a couple of months to get back up there.

Cushcraft A50-3S

A50-3S standing ready.

A year ago I found a deal on a used Cushcraft A50-3S. I managed to scoop up this barely-used antenna for $80. It was missing the mast U-bolts, which set me back about $10 from Cushcraft. For less than $100, I had a functional 6m beam, which languished in my basement for way too many months.

I fixed that problem the past weekend. I got the 6m beam outside, put it on a mast and checked the SWR. My dimensions came out perfect, as the SWR curves were exactly where they were supposed to be.

The mast was something I had lying around. It originally supported a Butternut HF-4B beam and a long 17-element F9FT 2m beam. That was a long time ago - about 25 years.

The mast consists of two 10 foot sections of EMT. I would normally not recommend using EMT as a mast material. It's not a structural support, and the metal alloy is fairly ductile, as it is meant for bending. For really light-duty service, it can be adequate.

Sawhorses make for quick tune check

I don't remember the exact sizes of the tubes. I think the bottom tube is 1 1/2" EMT, and the top is 1 1/4" EMT. The top tube slides easily into the larger bottom tube. A 1/4" bolt about 12" from the top of the larger tube supports the smaller tube, giving an overall length just shy of 19 feet. An EMT coupler with some long bolts keeps the smaller tube firmly against the wall of the larger tube.

With the mast across the sawhorses, and the reflector just off the ground, the antenna is easily checked for tuning.

With that done, I just needed a way to hold the mast vertical. I already had an eight foot mast in the yard that used to hold the Cushcraft R7000. With a couple of short pieces of rope, the 19 foot mast was lashed to the eight foot mast. And, voila!

The lashings hold the mast firmly, but it can be rotated by hand. (aka Armstrong rotation) It may only be temporary for now, but it works quite well. I put many 6m stations in my log this weekend on FT8. It's good to have a real 6m antenna!

Things I've Learned about Antennas - Horizontal Antennas

I've been fooling around with radio for more than 40 years. Finished my first receiver January 1971, so I guess it's closer to 44 years. In those early years, I didn't know anything about antennas. My initial antennas were nothing more than magnet wire strung up around my attic bedroom. They worked - Badly.

Over the years, I've learned a few bits of wisdom about antennas. This article is about:

• Horizontal Antennas

Be they dipoles, center-fed Zepps, yagis, quads, Vee beams or rhombics -- horizontal antennas share one key characteristic -- their most important dimension is height above ground in wavelengths.

The height determines the radiation pattern, impedance and much of the loss. I remember a few years ago on the QRP mailing lists there was a hot debate about one of W4RNL's designs -- the "88 foot" dipole. When LB modeled this antenna -- meant to be a secondary or spare antenna when your beam failed in the middle of a contest -- he did so at 100 feet and also at 70 feet. 

This design was supposed to give reasonable performance on 80, 40 and 20m. 88 feet worked out to be about right. Long enough not to have too crazy impedance on 80m, and short enough to not have a lot of deep nulls on 20m. At 100 feet, I bet it is a pretty good performer. At 70 feet, it wasn't a slouch, either. The odd-ball impedance would make for some loss in the feed line, but for a spare antenna, that wasn't a huge concern.

From the discussions, you'd like that 88 feet was somehow a magic number that made everything work better. Heck, if you have the room make it a full-size 80m dipole then add a couple of traps, for pete's sake. And do you think those QRP stations put up that 88 feet of wire at 100 or even 70 feet? Heck no, they were down at more practical heights of 20-35 feet. 35 feet might be passible for 20m, since it is 1/2 wavelength up. But it is only 1/4 wavelength for 40m, and 1/8 wavelength for 80m. 

Here's the deal: the pattern of a dipole is hugely affected by the height above ground. About 1/2 wavelength, it just starts to have a bidirectional pattern, and only that at pretty high angles. Lower than 1/2 wavelength, it's basically got an ice-cream-cone shaped pattern going straight up. This pattern is rarely desirable.

How high is enough? At some point above about 2 wavelengths, the dipole pattern looks a lot more like free space. For beams, at these heights, you can start to get nulls in your pattern at useful angles, so you have to be careful. Somewhere between 1/2 and 2 wavelengths is generaly the "sweet" spot for horizontal antennas. For specific applications, your best bet is to model the antenna at the desired height and watch for undesirable nulls.

Given that most hams don't have supports for antennas above 50-70 feet, it's likely that any antenna below 20m is too low. Get those antennas as high as you can.

Cushcraft A3S/A743 Performance

A3S/A743 pointed toward Europe.

Jerry, NG6R, e-mailed me this week in response to my posting on the Cushcraft A3S/A743. Jerry had sold his A3S to another ham who was wondering about getting the A743 add-on kit. He wanted me to share my experience with the antenna.


The specifications don't really change with the 40 or 30m add-on. This was true with my experience. I did the A743 update in-place, with the antenna still on the tower. (Something I'll share in another posting)


The performance on 20/15/10 was the same as before the update. On 40m, it is a dipole -- but a rotatable dipole. Beamwidth is pretty broad, about 100 degrees. There are noticeable nulls off the ends -- and some of that may depend on how high the antenna is mounted. Mine is at 15m (50 feet) high, which is still a little bit low for a 40m antenna.


If you can mount an inverted V or dipole significantly (8-15m) higher than the A3S, you might be better off with a wire antenna than the A743. At my QTH, the 15m high tower is the highest point in the lot, so the A3S/A743 is a great combination. 


In the picture, you can see the 80/40m trap dipole coming off horizontally to the left of the tower at the 12m level. This dipole is broadsize NE/SW. With only 3m difference in height, there's not a lot of difference in the two antennas, with the higher antenna having a slight edge on DX. During some domestic contests, I would rotate the A3S/A743 to point NE, giving me 360 degree coverage on 40m with a flick of the antenna switch.


(The 80/40m dipole has since moved to the micro-shack in Floyd County, GA)


Does it work? You bet. I have 40m WAS and 113 credits on LoTW for 40m, virtually all of them on this antenna. I'd prefer a two-element short 40m yagi, but my tower installation doesn't allow it. The A743 kit only adds a few pounds of weight and increases the turning radius by about a meter. It's a good addition to most A3S installations.

The Tribander Experience

Most hams start off on HF with modest antennas. Perhaps a simple wire dipole, or maybe a trap vertical. These simple antennas can work, and often work well -- when installed at the proper height and with the appropriate number of radials, respectively.

But those starting off often don't have the experience to do things quite right. My first ham antenna was a simple 40m inverted V -- it followed the roofline of the house on 6" standoffs. The apex was all of 25 feet up -- and the ends were only a couple of dozen inches from the ground. It worked, but not well. With the 50 or so watts I coaxed out of my novice rig, it did OK. I also tried various dipoles strung between trees and buildings, random wires, even a vertical made out of a slinky.

Anyone who uses these simple antennas often dreams of something better. I thought that the guys with the tribander at 50 feet had the high-end installations.

When I bought my own house, I wanted to put up some good antennas. First was a 300 foot longwire at about 15 feet high. Fed with an L-network, it could load up on all bands -- even 160m. It did not work well. For a while, I used a "Loop Skywire" -- a 80m full wavelength loop positioned horizontally. This was about 15 feet up -- just barely higher than the longwire. It worked OK, certainly better than the longwire. But really, none of these were any better than my novice antennas.

Somewhere along the line -- I had an epiphany: for horizontal antennas, the most important single dimension was the height above ground in wavelengths. I built an 80m dipole and got it up in the trees about 45 feet high. This antenna worked great -- much better than the Loop Skywire -- and it only required two supports instead of four.

I eventually put up a beam. First was a Butternut HF4B. It was mounted on a roof tower at a height of about 35 feet (10m). Certainly not optimal for a tribander. I eventually replaced the HF4B with a Cushcraft A3S. I've written about this antenna before -- it is probably one of the best of the small trapped tribanders.

When I moved to my current QTH, I decided not to repeat the roof tower experience. It took nearly seven years before I could save up enough to put up the tower. In the meantime, I used a number of dipoles at successively higher heights, a trapped vertical (the Cushcraft R7000), and even a couple of two-element delta-loop wire beams in the attic for 15 and 10m.

During this time, I had the fortune of being able to guest op at W4AN's superstation near Dahlonegah, GA. NQ4I also invited me to come and operate at his Multi-Multi station. These stations have multiple mono-banders for each band, often at heights much greater than your typical tribander-at-50-feet, and many times stacked mono-banders to certain areas. Operating at a super-station is pretty amazing.

Moving from a simple dipole or vertical to a tribander is an eye-opening experience. With a tribander, the band opens earlier, stays open longer, you have directivity that can bring stations out of the noise or null out unwanted signals. Bands you thought were dead come alive with signals. Pileups that were too big and crowded with a dipole are easily busted with the tribander.

It's curious that going from the tribander to monobanders or even stacked monobanders isn't as dramatic as the shift from a dipole to a tribander. Using a monobander or stacks is much like the tribander, only better. It isn't a sea-change.

Not every ham can afford towers and stacks, but every ham interested in HF ought to consider putting up a modest tower with a tribander. It will make a huge difference.