K9YC said:
"But it does show trends that can help us think about the viability of
vertical antennas..."
The FCC conductivity map indicates a conductivity of 4 mS/m for N6LF's
QTH in Oregon. In January Rudy measured 22 mS/m at 1 MHz in his field.
The map indicates 15 mS/m for AE5CZ's QTH in New Mexico. Larry measured
0.45 mS/m at 1 MHz in a sandy wash near his home.
Because of gross discrepancies like these, I think both the FCC map and
the ARRL ground constants are worthless.
If you don't want to measure your own ground, I think the best
alternative is to use the Hagn generic ground constants. I have no way
to verify their accuracy, but they were devised by a professional who
performed ground measurements worldwide for years. This writeup shows
graphs and tables of the Hagn values, extrapolations to LF/MF/VHF, and
provides a link to Hagn's paper that describes the theory and
measurements underlying everything:
https://k6sti.neocities.org/hfgc
Brian
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