I've updated my writeup on HF ground parameters. I revised the
extrapolation of 1 MHz FCC data to the HF ham bands. I also added data
for seawater and freshwater, both of which vary considerably with
location and temperature.
The latest edition of the ARRL Antenna Book has generic ground
permittivity and conductivity curves for 2-30 MHz developed by George
Hagn of SRI International in the 1980s. In my writeup I reproduce the
curves but add grids that make it much easier to pick off values for a
particular ham band. The curves provide an alternative to the
extrapolated FCC data. For some ground types the two differ
significantly. For example, the Hagn curves for rich agricultural land
are much closer than the extrapolated FCC data to the high values N6LF
measures with a ground probe on his bottomland in Oregon.
http://ham-radio.com/k6sti/gndp.htm
Brian
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