There is at least one internet project with photos of a double PI net
balanced tuner, which should work quite well. It uses copper tubing for
two large inductors and transmitting sized variable capacitors.
The 135 foot wire or a close to that length dipole will work close to
the ground for NVIS. Feed it with 450 ohm or 600 ohm open wire line for
all band use.
Working at 1/8 wave above soil, brings as signal to noise gain, in that
"skip static" from Summer thunderstorms is greatly attenuated or not
picked up at all.
NVIS brought back 80m to usefulness for Field Days due to the reduced
noise floor when the antenna was 5 to 6 feet off ground with a reflector
at grass top level. (after mowing).
-Stuart Rohre
K5KVH
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