Just a follow up on previous messages regarding the 4-square I built...
1. When I cut my RG11 coax, I cut to length using an SWR anaylyzer for the
proper length. It was several feed different from the suggested length in
the manual that came with the 4-square box. I would suggest not just
cutting it to a calculated length.
2. It is suggested that you tune the verticals for 10% below the desired
frequency of operation due to mutual coupling. In my case it didn't seem to
be anywhere near 10%. More like 50KC on 80M. So I tuned mine for 3475Khz
and 3775Khz. The low dump power point in both cases is 50KC higher.
3. I originally tuned mine for 3650Khz with the idea that I would live with
whatever dumped power there was on each mode. After the first weekends
evaluation I felt like I was loud on CW but not so loud on SSB. I also
didn't see as much F/B on SSB. The next weekend I tuned the array for SSB
and the only test was the contest. It worked FB.
This weekend I decided rather than simply adding length to each vertical to
move it to cw, that I would add a coil on the bottom of each vertical and
short across it when operating SSB. I wound the coil on a piece of plastic
pipe (about 5" in diameter). It only took a 5 or 6 turns to bring it from
3800Khz to 3525Khz. It also means that my verticals are truely vertical.
If I added length to each vertical wire, my supports were not tall enough to
keep the verticals vertical. They would slope in slightly. I figured
keeping the system vertical was more important than a whatever small loss
that would be seen in the coil. I hope I'm right. (any comments?)
4. K8CC told me that K3LR had problems with his 160m array detuning his 80M
4-square. I have a 160M sloping vertical about 30' away from one of the
legs of the 4-square. I have not seen any difference in dumped power
between any of the positions and the F/B seems to be consistant in all
directions. I'm assuming it's not screwing the 4-square. At any rate, it's
the only 160M antenna I have and it's staying up.
Hope this helps someone.
73
Bill
Bill Fisher, KM9P & K4AAA
http://www.contesting.com
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