Hello Happy Partisans,
UHF is a major part of the comms effort around here and I put in extra work to keep that part of our game improving. This weekend I decided to build a Yagi antenna using material within ten feet of where I was standing in my kitchen when the idea struck me. A closet produced an old wooden yard stick and a handful of flimsy metal shirt hangers. The junk drawer offered rubber bands, side cutting pliers, poorly sized crimp ring connectors and a calculator. I cheated with the split post BNC adapter, aka cobra head, since that was down the hall and more than ten feet away.
Half an hour later I was up and running. As you can see in the photo Yagi math allowed me a six element unit using what I had. I built it for 460 Mhz and 462 gave me an SWR of 1.08. Dropping to 442 moved the SWR to 1.27.
Dimensions for those who care are 12 inches for the driven element, cut evenly in half with rings crimped on the end. I filed off some hanger enamel before crimping for a better connection. I also cut down and reshaped the ring connectors as they were too large for the posts. 12.75 inches for the reflector and 11.5 inches for each director element. Rubber bands hold each element in place. I read somewhere that antennas with 4 or more elements do better with .25 wavelength spacing instead of the usual .15. .15 gives a 10Db gain and .25 amps it to 27Db, but can’t prove that. Anyway .25 gave me 6.5 inches between elements and the SWR results are fine with me.
Feel the need to learn how to make this stuff and use it properly? I know somebody who offers a class for that. Your disaster plan will thank you.