> 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. _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK