> I've been looking for a portable commercial ground tester (3 point or 4
> point) that measures ground resistance at RF frequencies rather than the
> normal near-60 Hz frequencies.
60Hz measurements even when "corrected" to RF are totally meaningless. I'm
not sure RF measurements of rods are actually effective either. While I'm
not experienced with the very rare and expensive RF test sets that are
around, logic tells me the cross-section of earth sampled would be too small
at 1.8MHz to be effective unless you made dozens of measurements.
BC stations measure conductivity of soil with a test antenna by measuring
the slope of attenuation at increasing distances with many dozens of
measurements on several radial paths extending out several miles, and
comparing the measured slope with estimated losses in calculations. The
result is a distance-averaged soil conductivity.
>From the estimated conductivity, the actual FS of an actual antenna is
corrected to the performance it would have over perfect soil. The difference
in projected signal level at a certain distance (usually one km or one mile)
for that estimated conductivity to actual FS for that estimated loss gives a
crude estimate of array efficiency.
That method is generally within a few dB if people do things right, but
unfortunately they often don't. (Especially when trying to prove a point!)
However, even all that work only provides average soil conductivity over
distance rather than Fresnel zone conductivity that is important to us.
I'm not sure what you are after, but maybe there is a more direct way to
find what you are looking for, rather than learning actual ground
conductivity over distance which won't mean much for us anyway.
73 Tom
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