Once again summer is drawing to a close and I have not completed
half what I set out to do. And once again I'm looking for a little
nudge in the right direction to speed things up.
My new 160m transmit antenna had a rather severe impact on
performance of my Beverages, which are in close proximity to it. The
vertical is 98 feet of Rohn 25 with a short mast and 7 element 6
meter beam sitting at 101 feet. My attempts to measure the resonant
frequency of this structure were not successful. It is fed by a
three wire gamma cage which extends to 60 feet. The tap to the tower
is at 32 feet. I have two questions:
1) Any advice on how to go about detuning this? Perhaps someone has
had experience with a similar structure? I had thought of trying to
use the gamma itself to isolate the bottom 32 feet, by switching the
appropriate capacitance from the bottom of the gamma section to the
tower base. Even if that works it still leaves 69 feet of vertical
structure with top loading. Should I be looking at isolating a
section further up the tower instead? Any thoughts would be most
2) Are there any issues I should be aware of in trying to switch the
detuning network at QSK speeds with a control line of some length?
The base of the tower is 250 feet from the shack.
Thanks & 73,
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