In a message dated 12/16/02 1:30:09 PM Eastern Standard Time,
[email protected] writes:
<< Dick has indicated that Earth Resistance gets higher when the ground is
wet. That seems strange and contrary to accepted theory. The ideal ground
plane for a vertical is on a wet plain or preferably positioned in the middle
of a lake or in the middle of the Ocean. Have I missed something and read his
observation incorrectly. >>
I think both points of view are correct, but under differing prevailing
conditions.
The type of soil may make a great difference in whether moisture enhances or
degrades radiated signal. Where I live now, the soil seems to experience
increased dielectric loss when wet; whereas, in other locations, I found the
opposite to be true. Because of the greater skin depth of the earth as the
wavelength increases, I would expect the effect to be more pronounced at LF
than MF or HF. Dick's data may be partial supporting evidence that this is
so; in which case, it's even possible that some soils will be better at MF
when wet, and better at LF when dry. Sounds like a fertile field for
investigation (no pun intended).
As for bodies of water, a freshwater lake turns out not to be as good a
location for a ground plane as I once thought. I have tried this approach at
LF and MF at a few very different locations, always with less signal than
expected.
Seawater is quite a different matter! At MF, especially, it does truly
wonderful things for signals. Along with our fleet of VHF FM public
broadcast stations, I oversee one small mediumwave station on the Georgia
coast which is less than listenable more than about 20 miles inland.
However, it has a coastal coverage range from St Augustine, Florida, to
Hilton Head, South Carolina. (In fact, do we have any readers in Bermuda?
If so, I invite you to give a listen on 1190kHz.)
John
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