On 8/21/2017 11:53 AM, Joe Subich, W4TV wrote:
hat is installed on the top of the 115' tower? At 115' it's quite
close to resonant t0 2 MHz and any significant top loading (mast,
antenna booms even with insulted elements) may move the resonant point
down to 1.8 MHz or lower. It will most certainly couple heavily to
the inverted L and will seriously impact performance.
Given that you can not get the vertical part of either a "T" or inverted
L more than 30 feet (0.06 wavelengths) from one of the towers, I would
expect coupling to be significant unless you can detune both of the
towers.
Good thinking. I'll add a very different suggestion that works for me.
My tower is roughly equivalent. The solution I chose was to rig two
wires sloping away from the tower to a feedpoint about 60 ft away. One
goes to 70 degrees, the other to 270. They are suspended from opposite
ends of a 10 ft length of 4-in PVC conduit that sits just below the
rotator. The wires are fed separately at the base against 4 radials
elevated about 20 ft. The tower acts as a reflector, yielding about 2 dB
of gain. It's grounded, but I've added 8 on-ground radials to reduce its
resistance.
73, Jim K9YC
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