Actually, the conductivity is less important than the
velocity factor. A copper wire beverage above a (big)
copper sheet wont behave at all like a beverage because the
signals travel thru both sides at virtually the same time...
Its a traveling wave antenna that couples out the difference
between the signal in the wire and the signal in the ground.
Doubtless you actually have a reduced signal level out of
your antennas, but it may not be a whole lot if the soil
under your antennas is usually quite moist - or is quite
moist down just a few feet.. Guess what we all need to do
is put a HUGE mass of polyethylene under our beverages to
get the velocity factor down to 0.66, (anyone know the
velocity factor of distilled water? its 0.85 or 0.90, as I
recall)
Consider the case where several wires are run along the
ground under the beverage to "normalize" irregularities in
the ground - the primary effect is a decrease in the
difference in velocity factors resulting in less signal per
foot.. that's why it takes typically 4 wavelengths in that
situation to be have like a "regular" 2 wavelength beverage,
specifically to have the same pattern..
In any case, I'm glad to learn that even over semi pure
water that they still work usefully.. The experience I've
had was inconclusive from a beverage standpoint since the
wire along the lakeshore at XZ1N was not long enuff. It was
pretty insensitive which I attributed to the water (water I
sure wouldn't swim in, let alone drink!)
Robin, wa6cdr
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