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k6sti
08-03-2013, 02:34 PM
I've posted a writeup for three FM log-Yagis here:

http://ham-radio.com/k6sti/logyag.htm

I designed these antennas to minimize rear response over the whole 88-108 MHz FM band. They have very low backlobes but relatively low forward gain. I believe most FM DXers are limited by interfering signals, not by lack of signal strength. You can compare their forward gain and front-to-worst-backlobe ratio with those of other antennas here:

http://ham-radio.com/k6sti/curves.htm

Each of the designs requires a phasing line. I specify 1/8" aluminum wire spaced 1/2". I thought fabricating this line would be the most difficult part of building one of these antennas. But Mike-CT had a better idea. He built an earlier design using parts salvaged from old antennas, include the phasing line. The design he built specified 1/8" wire spaced 1". Turns out the impedance of Mike's salvaged phasing line isn't that far from the impedance of the specified line! The writeup includes a photo of Mike's antenna.

Brian

egrabow
08-04-2013, 11:19 AM
Thank you for all your work on that site. It'll come in handy for me as I plan an FM setup over the next year.

k6sti
08-07-2013, 11:49 AM
Vertically polarized log-Yagi stack:

http://ham-radio.com/k6sti/vstk.htm

Gain and pattern comparisons:

http://ham-radio.com/k6sti/curves.htm

Brian