>Sounds good at first glance, but how do we determine the dipole's height?
>I.e., Where is the "ground" -- at its surface? Five feet below its
>surface??? I would venture to say that as its conductivity improves, the
>closer to the surface it is. 73, de Earl, K6SE
Good point Earl. Any ground other than a metal plate is going to have varying
levels of absorbtion loss and delay. 160m RF has been detected as deep as 40+
feet below ground surface.
As it would be difficult to place probes at various depths below the surface
for taking measurements, I would suggest driving a short vertical dipole at a
specific low power, and taking field strength measurements a couple wavelengths
out. The weaker the field strength, the more ground loss present. Of course,
other above-ground RF absorbers and reflectors would have to be taken into
account, as well as existing radials. Standards of measurement could be
developed. This may be similar to Broadcast procedures already in use.
After having dug several holes around this 1/3 acre lot, I can say that I have
found sand, black loam, red clay, wet soil and ocean bottom, in completely
different percentages of makeup and depths, at each location. If this is the
norm, ground loss will have to be taken as an average number for an
omnidirectional antenna.
73, om Doug / NX4D
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