Be careful using feed systems that connect the coax between a few elevated
wires and the tower structure itself.
Nothing stops current from flowing in the tower BELOW the connection point,
as well as above the connection point. That means you have out of phase
currents in the vertical (the radiation effects subtract from each other).
A second problem is considerable current can flow from the base of the tower
to the lossy ground.
You can model this on programs like Elnec by inserting a resistive load in
the ground connection at the base of the tower. (Most programs treat the
earth connection loss as zero ohms unless you do this.)
The best feed system would be a gamma match, if you can not insulate the
tower at the feedpoint.
73 Tom
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