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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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