Just a comment on the attenuation slope method.
When the ground characteristics are dominated by conductivity, as they
usually are at BC frequencies, the slope method is pretty reasonable.
It gives good information on average conductivity but little for
permittivity. At HF, where the ground is often affected by both
conductivity and permittivity (Er), you find that when you try to
curve match to the field data to derive the constants there are often
multiple sets of parameters which can fit equally well! It doesn't
work very well.
Interestingly enough, if you go higher in frequency the ground becomes
Er dominated. Now you can get information on Er but not much on
conductivity!
The buried vertical dipole is often used when a bore hole is
available. Not much use to hams unless you happen to have a few
uncased wells distributed around your property.
On Doug's comment on the variability of the soil around his QTH.
Mines the same and I suspect most places are. That's why I feel we
need to settle for average characteristics over some area rather than
a few spot measurements.
73, Rudy N6LF
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