I am not sure how accurate this is but I usually model the tower as a
large diameter wire and I only include the boom of the top antenna (I
use insulated elements). K9RS has an interesting article on using
bent wire verticals around a tower
https://www.kkn.net/dayton2008/multi-element%20lowband%20verticals%206.pdf
John KK9A
k4xs wrote:
Plans are VERY slowly progressing for my new station in Belize. Plans
are for a 106 foot tower with lots of goodies on it.
Here's what is planned:106 ft of Rohn 55 guyed with Phillystran.
Three swing armed Skyhawks at 32, 64 and 96. Two A3WS WARCs at
around 76 and 42 ft. I plan on running four ropes to hold a wire 4
square surrounding the tower. This is similar to what I had in KH6
and the 4 square worked well although the F/B was down to around 10-12
dB.
My question is this: I know the tower will have some effect on the 4
square surrounding it. Obviously I don't want the tower to be
anywhere near resonant on 80. My guess is the top loading of the
tower will lower the resonant frequency quite a bit, and the effective
height will be around 145-150 ft, but I am not sure. Obviously if it
is in the range of around 130 it would be a big issue.
There is not enough room to put up a 4 square by itself so I'm stuck
with this set up. I do have some fiberglass poles that I could attach
to the tower vertically to give it another 13 feet or so by running a
wire up the pole and attaching it to the tower, but I really don't
want to do that if I don't have to.
Thoughts on this?
73 Bill K4XS/KH7XS
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