At 02:10 AM 3/18/02 +0000, you wrote:
>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..
>
I've used medium wave Beverages (partially) over Pacific Ocean salt water,
and heard plenty of DX. There was no scientific comparison made by putting
up a nearby Beverage over poor ground, as this was a very temporary wire (a
few hours).
But, do not arriving skywaves have a horizontal component anyway, which is
what is needed to make Beverage antennas work? Weren't Beverage's
original experiments done with rather long vertically polarized waves which
only acquired a horizontal component if the ground underneath the wire was
of poor conductivity. At higher frequencies, is the poor ground nearly so
important?
Could experts on the list please clarify?
best wishes
Nick
VE7DXR
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Nick Hall-Patch
Victoria, B.C.
Canada
e-mail: Nick_Hall-Patch@telus.net
(mail forwarded via nhp@ieee.org)
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