A 6m beam for portable operations

There is always a need for another antenna. If this does not sound like a self evident truth you are probably reading the wrong blog.

For a while I had been contemplating building a new 6m beam. I have the DK7ZB multiband beam for 2-4-6 meters. When I made it, I thought it would be a nice addition covering these three bands. In practice however I found I don't really use the 2m and 4m bands and therefore have an overly complex antenna with 7 elements while only using it as a 2 element 6m beam. To make it transportable I have to remove (parts of) the 4m and 6m elements. With the 2m elements the antenna is rather bulky to transport.

I was looking for an antenna for 6m with more gain but less complexity in assembly and one that would be easy to transport. One of the things I wanted to avoid was having to use bolts and (wing)nuts to attach the elements - as these small parts have a tendency to go lost when you drop them while out in the field.

My ideal "high gain but still transportable" option came down to a 4 element antenna with a boom of 4m. Split in two the boom is transportable. The same goes for the elements. Now all I needed was a way to attach the elements without using any loose parts.

I remembered an old 11m vertical that had radials you could screw into the base. What if I could make some construction to be able to screw the elements in position?

Keeping the antenna light (it is for portable operation) I chose 8mm diameter tubes for the elements. The inner diameter of this tube fits 6mm metric threaded rod. Glueing these in I had my threaded elements. 

Now for the other side I looked at a threaded rod extension (coupler). There is a round version and with the 6mm threads it snugly fits in a 12mm diameter aluminum tube. 

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With this concept working I continued developing the antenna by spacing the elements along the boom (using plastic element holders to attach the elements to the top of the boom) and making them to size.

For the dipole I used a plastic pipe to create a mechanical non conducting connection. I inserted the same threaded rod extensions I used for the other elements. In this case I soldered a piece of wire to the extensions - creating a connection point for the coax.

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I then created the quarter wave impedance transformer as specified by DK7ZB and put all the pieces in a small junction box. Note that I cut out an opening in the bottom of the junction box to be able to use an element holder for the dipole. That way I know all the elements are nicely in parallel.

In the end there is one spot left where this antenna has bolts and wing nuts: at the point the two boom parts meet. Perhaps I can design some other solution there in the next version.

Time will tell if the threaded connection is an improvement or that it will drive me crazy when dirt gets on the threads (quite imaginable in the field). For now I like the compact package the antenna constitutes while disassembled and I like the way I can quickly put it together.

After completing construction work I took the antenna out for a test. The results were peculiar to say the least. The VNA showed readings that were off and over the air tests did not correspond to the theoretical performance of the antenna.

Reacting to my first post about these results, Enno PF5X pointed out that not all glues are created equally. I used metal glue but did not take notice of the conductivity. Testing it afterwards I found issues with the conductivity on several elements.

Added metal screws to ensure a good conductivity

So I made a necessary change to the design: connecting the aluminium tubes and the inserts (the threaded rod and threaded rod extension) with metal screws.

You could argue that the whole gluing step can be skipped in this final design but I think it makes for a more robust construction - which is important for an antenna used portably.

With this new antenna I went out last Saturday as the IARU 50Mhz contest was on. I also took my 2 element beam (actually a triband beam with 2 elements on 6m) for comparison.

PE5TT was available (again) for a simple test. At 25km distance with a comparable antenna we had the same signals both ways but s9+ this time (with design v1 it was only s7). Decreasing the power to 10w we could establish that the new beam has 2 s-points gain over the 2 element beam. We also found the F/B was at least 4 s-points. F/S was even more dramatic.

I subsequently entered the contest. There was some Es but most of it was too far south with weak skip to G. However I was able to check the beam's characteristics switching between the two antenna's. Confirming the 2 s-points difference. And even though signals vary strongly during Es conditions the practical F/B performance was apparent as even the strongest stations from S-Europe almost disappeared once I turned the beam to G.

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First 4m QSO - getting a transverter kit working

Almost a year ago I bought a 4m transverter kit from DF2FQ (XV4-40). I have basic understanding of electronics, acquired in part through the hobby but building a project like this was new to me. With my mechanical engineering background I am more confident in building robust stuff like antennas, masts, supports, baluns, etc. Soldering loads of tiny components on a board seemed challenging. 

However the level of documentation provided by DF2FQ and some motivating words by PG8M - who was already using the transverter - pushed me to the point that I ordered the kit. When I received the package I must admit it looked daunting. 

Lots of parts..

..and rather tiny

I started building the kit sometime in August last year. I tried to work as meticulous as I could (a challenge when you are as impatient as I am). When I had completed the kit and ran the first tests, I found that I received 70 Mhz signals with the radio tuned to 29Mhz. Hurray!

However, when I tried to transmit, the transverter appeared to be dead as a dodo. No LED, no signal. A very disappointing result. I did some tests (as far my knowledge goes) and could not find the cause of the failure. So the kit went back in the box it was shipped in. Time for other projects.

The Es season is rather good this year and I have enjoyed the effects on 6m but 4m was open a lot of times as well. I really had to get back to the abandoned transverter project. PG8M had already kindly offered to help me months ago and today I took him up on his offer. We went through the error checking process step by step, finding and fixing four major issues. It turned out I had made two soldering errors and two of the smd resistors were faulty. Whatever happened to these resistors I really don't know.

PG8M trying to locate the next error

The good news is that we ended up with a transverter that delivered up to 35W on 4m with 5W drive on 10m. 

There was no one around to do an on air test so back home I hooked up the transverter and put my tri-band yagi on a pole @2m high in the garden. PG8M was QRV 30km away with his 4 ele beam pointing in my direction. That is when I made my first 4m QSO.

DK7ZB tri-band beam in action twice this week

It is a bit late in the Es season but I am sure I will get back to this band in the future. The next thing I need is an antenna I can set up quickly at home in case of any high MUF situations. For 6m I use an end fed wire that I can attach to a pole that I push through the attic window. For 4m I am going to try a slim jim vertical. More on that later.

Playing with 6m Es - compact beam versus vertical

Some time ago I built a compact beam for 6/4/2m aimed at /P operations. It is a design by DK7ZB featuring 3 elements on 2m, 2 elements on 4m and 2 elements on 6m. I tested it when I finished building it and SWR was good on all bands.

I followed the design of DK7ZB (link) with a few changes to make this a /P antenna:

• I use wing nuts on the 4m elements and the 6m reflector to be able to remove them easily for transport
• I split the 6m driven dipole in a short center piece connected to the boom and removable parts on both ends of the dipole
• I added spacers for the dipoles to keep them at the right distance from each other (refer to picture below)

Spacer for the dipole elements

Apart from a short appearance in LX (2 QSOs), I had not used the beam on the air. For 6m I use an end fed half wave vertically - both when I am /P as well as at home.
It is amazing how effective a vertical wire is in Es conditions. I have worked stations all over Europe with that antenna using 100w. I was curious how the beam would perform in comparison.

We are in the Es season at the moment and there was a 6m contest on last weekend. So I decided to go out /P and test the beam properly against the end fed wire. I used one of my Spiderbeam poles with the end fed wire in the top (feedpoint about 12m high) and the beam a bit lower at about 8m high.


I used an antenna switch to be able to quickly switch between the two antennas. You need quick switching as the signals themselves vary constantly under Es conditions. The difference was significant most of the time. Of course the heading of the beam is a factor that influences the difference. With the beam heading the right way, the signal strength on rx differed multiple s-points. On the low end this meant there were stations I could only copy on the beam. I recorded a view video's while switching between the antennas. One of them is on YouTube:

With PG8M - who lives just under 30km from where I was /P - I tested the characteristics of the beam via ground wave. We found a difference of 2 s-points front to back and 5 s-points front to side.

All in all this shows me that this beam is definitely an interesting antenna to use in the field for 6m. It is light, easy to set up and relatively easy to transport. As the 6m reflector is rather long for easy transportation I am thinking of splitting the reflector in two or three parts.

While I was testing this setup I logged 25 stations, collecting 10 new grid squares on the go.