On Mon, 18 Sep 2006 12:43:00 -0400, Herb Schoenbohm wrote:
>Suggest a resonant circuit with a 50 ohm feed line tapped up a few
>turns from the grounded side. Since this is outside a small WX
>proofed plastic box of the appropriate size may be needed. Also
>you might consider, depending on you ultimate power levels,
>determining the required C needed with the coil with a low power
>capacitor and then switching in a good Mica HV cap such as a G2.
> This antenna you describe should be a real performer on 80 meters.
Yes, after I posted the question, I went "into the woodshed" --
looking through ON4UN's book and the Antenna Book, and found exactly
that suggestion for a very similar configuration. So I built it up,
winding the 9 turns of #16 enameled wire around a 2" piece of PVC
plumbing pipe (it's the biggest enameled wire and coil form I had in
the junkbox), tapped it up a bit under 2 turns, hung a HV
transmitting cap across it, and fired away. It loads, but something
in what I built is VERY unstable over time with applied power so the
Z doesn't stand still long enough for the tuner to load it. I
changed the cap, so I suspect the coil form. I felt it carefully
after hitting with 500w for a 30 seconds or so, and didn't feel any
heat. Strange.
I'll try it again with bigger wire that doesn't need a form.
Thanks and 73,
Jim K9YC
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