Hi Jim,
thank you for reporting these very interesting experiments. I wonder if you
could optimize the shielding effectiveness of the counterpoise by connecting
it via a variable inductor to ground, thus inducing an adjustable
opposite-polarity voltage to nullify the displacement current into the earth.
If I remember right, the technique was shown in the circuit diagrams of SAQ's
antenna system. - A few years ago, we applied the same principle to
effectively neutralize a tetrode amplifier at 40 MHz, using its screen-grid
lead inductance.
My LF antenna is mostly above our roof, which has a thin aluminium
vapor-diffiusion barrier beneath it. A while ago I found that explicitely
connecting parts of the foil to TX ground reduced the antenna resistance from
32 to 30 ohms (and less noise-pickup from devices within the house). Judging
from the large variations seen during frost periods, I believe a large part
of the remaining loss is due to the capacitive coupling to nearby trees.
73
Markus, DF6NM
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