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.