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Old June 17th 08, 03:13 PM posted to rec.radio.amateur.moderated
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Posts: 236
Default Antennas - Is NVIS a good thing?


"Bill Horne" wrote in message
t...
Thanks for reading this. I've just been through a very confusing antenna
trial, and I'd really appreciate some info from hams who know more about
them then I.

My brother, W3TDH, called me up yesterday and asked me to help test some
80 and 40 meter antennas that his club is preparing for field day. He told
me that the club is going to serve their target coverage area by using two
dipoles, spaced 1/2 wave apart and fed in phase, so as to maximize NVIS
(Near-Vertical Incidence Skywave)radiation.

I'm not arguing with the design: antennas spaced 1/2 wave apart and fed in
phase always have maximum radiation at right angles to a line bisecting
both antennas. Ergo, two dipoles, horizontally mounted, etc., will indeed
produce their maximum radiation straight up and down.

My question is: why would that be the best design? I thought that NVIS
radiation was a byproduct of having a radiator less than 1/2 wave above
the ground, and that it wasn't to be sought after, but rather avoided.
Leaving aside the losses due to 1/2 the power pointing straight down, why
would an antenna on 80 or 40 meters be most effective by radiating almost
straight up? Wouldn't the coverage be improved by phasing the antennas so
as to maximize radiation toward the horizon?

73,

W1AC

--
Bill Horne, W1AC


------------

It's just a W.A.G., but most of the old publications reflected the culture
of the time and the culture in those days was oriented to working DX, not
locals. Today, I enjoy talking out to several hundred miles much more than
speaking to someone a continent or two away who is restricted (many times)
as to what they can or cannot say by their government. Then throw in foreign
accents, my aging hearing, etc., and one understands why speaking with my
fellow Americans is a much more pleasant experience - most of the time. I
mean no offense to foreign amateur radio ops. I enjoy speaking with them
too, when in a relaxed, non competitive atmosphere.

Ed, NM2K

 
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