Regardless
>of the validity of modeling, it is certainly true that having an
insulator
>right under the antenna at the top of the tower results in a
high-impedance
>point probing a location with maximum RF - thus tending to
maximize any
>potential problems whereas with connected guy wires there will
tend to be
>at least partial cancellation of the fields caused by the three
guy wires
>and the tower.
>
Whether it results in a high impedance or not depends not only on
the insulator or lack of, but on how high the tower is and how
long the guys are and if they are grounded on the bottom or not.
In addition, the coupling to the antenna can be through the
electric or magnetic fields or most likely a combination of both
(i.e. hi Z or lo Z). At 20 meters it only takes 16 feet to go
from a low impedance to a very high impedance. With a tower and
3 sets of guys differing in length, it's a fairly complex
situation. I used the presence of substantial current in the
guys as the indicator that there was interaction. How it got
there was not important.
George
W2VJN
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