Build your own 435MHz Yagi-Uda

Why is it that antennas cost so much money? When you get them home and have a look at them you struggle to see where your money went. When I looked for a pair of 11 element beams I found that they would set me back over $300. Screw that! So off to the Internet I went to look for some homebrew antenna designs. It wasn't long before I came across this one from ON1DHT which I promptly set about building it.

I had recently removed an old TV antenna from from roof of my house and it was lying in a heap on the garage floor. It looked like it would do the job so I set about hacking it up. Wonderful things, power tools. 10 minutes later the TV antenna looked like the pile on the right.

Measuring tape and pencil in hand I set about converting the pile of junk into 2 antennas.

Back in the summer I went to a tool sale at the local Knights of Columbus hall. For $50 I came back with a 4" angle grinder, a 4" 2 wheel bench grinder and a drill press. Not too shabby!

This was the first time I have used a drill press since I was at school. I should have spent some more time looking at it before I bought it. The vise that came with it wasn't big enough so I had to buy a larger one and then clamp it to the drill table with some 'C' clamps.

The drilling bit was the easy part. Measuring the elements was the difficult bit. I used a pipe cutting tool to cut the elements down to size. Good job I had to repair a burst pipe back in the spring otherwise I would have had to do this job with a hacksaw.

The antennas turned out to be ok. New antennas they are not but made by my own fair hand they are. The design calls for a dipolebut that would require isolating the driven elements from the boom. Not something I was wanting, or knew how to do. Every beam antenna I ever saw had either a folded dipole or a gamma match as the driven element. As a gamma match would be easier to make I built one of those. I used the dialectric from the inside of a piece of RG8 coax and an off cut from the elements. It worked out just fine. I used an SO-239 socket for the antenna connector as I could not find any N type connectors. I dunno how much loss I have but it doesn't seem to be a problem.

The only test equipment I have for the 70cms band is my DWM-4 watt meter from LDG. I bought it as a kit a few years back and its been a really usefull tool ever since. As you can see the antenna tunes up fairly well.

© & ® Mark A Phillips, G7LTT 1997/8/9/2000/01/02/03
This page was last updated Thursday June 26, 2003 07:45 Eastern Daylight Time