> Richard Fry, you know anything about this? A 5:1 change in soil seems way
> out of line with what I recall from fields at WSPD on 1370 kHz and WOHO on
> 1470 kHz. Were those stations exceptions?
I don't know about further out where you'd have to proof an AM station
but I just ran some models and there's kind of a weird relationship
between vertical electric field strength at 1 wavelength out and far
field efficiency as ground conductivity is varied for fixed
permittivity.
http://n3ox.net/files/1500kHz_monopole_cond.png
This was a #12 copper wire monopole fed over 64 0.5wl radials 1 foot
high. Power is held fixed at 1000W. The reference "0dB" case for both
the vertical field measurement and the far field efficiency was their
equivalent values over perfect ground, but with copper wire loss
turned on, so the reference far-field case was about 82% efficient.
I want to try different distances and a higher frequency like 40m
because I think the results will be quite different. Would also be
good to, instead of looking at the total radiated power, compare the
far field gain at some elevation angle vs. total field at that
elevation angle nearer the antenna. But at any rate, seems this
plot is relevant to what you can deduce comparing FS measurements over
different soils.
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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