You now have multiple responses and you can believe all of them. I have
the same half-sloper connected near the top of my 55' crankup (suspended
several feet from the top, to increase the distance from my SteppIR). It is
OK, but I cannot claim it is great. As others have noted, half slopers
are almost impossible to predict. Remember that the tower is part of the
antenna and tower grounding (meaning radials) is part of the equation. As
best I can tell, it has not affected my beam operation.
I suspect that part of the unpredictability is due to the coax position.
Mine, for example, runs down the tower standoffs. The external part of the
coax shield is also part of the antenna, like it or not. The coax is
parallel (about two feet) to the tower (which is also part of the antenna).
The tower has radials at the bottom. The coax is not grounded at this point
(I know, I know, it should be for lightning protection) but goes
underground and the underground run may act for decoupling. This is all
very messy to try to analyze or model.
Bill - W2WO
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