Might well be, though, that a 18" or 2' high wire is much easier to deploy in a field situation, than trying to get a wire up 1/4 wavelength on 40 or 80? From a system standpoint, you might be willin
I once put up an ionospheric sounding antenna in Puerto Rico that was a complex wire array to cover 2- 30 MHz and it was strung between two 100 ft towers that I had installed in a flooded field. The
who a antenna the easier to deploy wavelength on 40 or accept the lower likely to be near it) If that is the advantage he had in mind, the writer would have said that Jim. He plainly gets into nonse
Not that THIS author knew what he was talking about.. The original inventor of the 18" idea (which has been around for at least 5-10 years, I think) was the one who decided that it was a "reasonable
TT: FWIW - Here's a possible source for the eighteen-inch-above-ground NVIS antenna fables: http://www.tactical-link.com/field_deployed_nvis.htm . 73 de Gene Smar AD3F _______________________________
Interesting.. " NVIS was originally evaluated by U.S. Army Forces in Thailand during the Vietnam conflict in the mid-1960's " Yup.. that would be George Hagn's work, I suspect. I ran a quick NEC4 mod
"average earth" up (9 dBi) dBi If you look at Hagn's actual measured data you'll see over 30 mS or 50 mS/m soil (very good earth) FS drops several dB as antenna heights move below .05 wl. .05 wl wou
TT: The distortion that is mentioned below and in (the poorly edited) QST article is actually alleged multi-path interference. The explanation I've read in a couple of sources is thus: When an NVIS a
Perhaps. I did say it was a quick model. I suspect that the better the ground, the more pronounced the effect. Or, more properly, there's some ground properties which have an optimum match to the fi
doesn't "real Jim, I think he does mean "does not propagate on ground wave". Horizontal polarization will not support a ground wave signal. It gets shorted out by the earth. A vertically polarized si
over dB the better the Not "perhaps", that's exactly how it is over wide variations in soil. Over Georgia clay in my pastures the earth losses just suck the signal away from a low dipole. In rocky C
Hmmm.. however, is it that the wave (launched by some mystery box) can't propagate over the dielectric boundary as horizontally polarized,OR, is it that a practical antenna can't launch a horizontal
box) can't propagate is it that a wave because it has Both. That _______________________________________________ See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Statio