Dennis,
To eliminate interaction with a nearby 10 meter Yagi on Rohn 45, the
first insulator must be not more than three feet from the tower. Ideally, the
next insulator should be spaced not more than eight feet
for optimum 10 meter performance.
As a rough approximation: consider the distance from the first
insulator, through the tower, to the first insulator on the adjacent guy wire.
This RF circuit acts as a parasitic element, end loaded by
the compression insulators and the guy wire loops through the
insulators. Ideally, the total insulator-to-insulator distance should
be less than 1/4 wavelength on the highest band of interest (eight
feet on 10 meters).
You can use EZNEC to more accurately model the effects of your guy system on
your antennas, but it will give you approximately the same
results as above.
73!
Frank
W3LPL
---- Original message ----
>Date: Tue, 4 Sep 2007 16:50:48 -0400 (GMT-04:00)
>From: DENNIS BRICKEY <n4dd@earthlink.net>
>Subject: [TowerTalk] Where to Plave the First Insulator in Guy Wires
>To: towertalk@contesting.com
>
>Ok Tower Gurus,
>
>I am erecting 120 feet of 45g and need to know where I should place the
>first insulator (the one closest to the tower) to minimize interaction with
>the antennas? I am assuming that it needs to be rather close to the
>tower. Any opinions?
>
>Thanks,
>
>Dennis N4DD
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