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Antenna Ratings
On Mon, 05 Jan 2004 02:02:17 GMT, Gary Schafer
wrote: All antennas are two terminal devices. There is no such thing as a single point feed antenna. Changing a horizontal antenna to a vertical antenna at the same height does not improve the radiation angle. If it did everyone would have their horizontal antennas in the vertical position. AM radio stations depend on ground wave signals not sky wave. A horizontal antenna theoretically does not have a ground wave so verticals are used for AM stations as they produce a ground wave signal. Hmm....I've been using horizontal antennas to transmit ground wave communications since I was 11 years old in 1957! All VHF and UHF TV stations use ground wave only signals and every one of them in the USA are HORIZONTALLY POLARIZED. Kinda blows that theory all to hell, doesn't it? Until very recently, all FM radio stations were all horizontally polarized, too, but that was changed because cars have vertically polarized antennas......or did when they changed the rules. Embedded FM antennas in windshields are horizontally polarized, a dipole. For sky wave signals height is important in order to produce better lower angle of radiation. Lower angle radiation provides longer hops. Depends on how far you wish to talk. I use very high angles of radiation on 3915 Khz to talk to my buddies around SC, NC and Georgia on 75 meters. This is easily possible because my inverted-V dipole is only up about 30', not much % of a wavelength when the wavelength is 240 feet long. Listen from 3.5 to 4.0 Mhz nights and 7.0-7.3 Mhz days and hear lots of us "high-angle-radiators" shooting the breeze, ad nauseum. Works great since 1957....(c; Adjusting the height to adjust the impedance of the antenna is not to be worried about. That's what matching systems are for. With multielement antennas (beams) the feed point impedance can be very low even if the antenna is high in the air. Some other means of matching the antenna to the line is required. Absolutely nothing radiates like a TUNED antenna, without the lossy tuner between feedline and antenna. Damned Navy has tuners so inefficient trying to load a flagpole whip they have to have BLOWERS in them to keep from melting them. All that power ISN'T radiated, obviously. I used to operate WB4THE/MM2 when I was a young sailor on USS Everglades (AD-24) back in the 60's. It was my call at that time. My captain never got over I could make phone patches to his wife back in Charleston through a friend of mine on James Island (K4OKD) with my $249 Heathkit HW-100 kit transceiver, even barefoot, when the Navy's million-dollar radio installation wouldn't. He used to tease the comm officer by saying to him, "I want to talk to Charleston. Can we do that?" Of course, the answer was no. "That's BS. I just talked to my wife on ET1 Butler's ham radio not 10 minutes ago! What's wrong with our radios?" The comm officer hated my guts.....and said so...(c; They used to listen to my homebrew quad 813s linear amp up in radio when the old man was on the air. The chief radioman used it, too.... Regards Gary 73 DE W4CSC/MM2 Watch out for those ground waves.....(c; |
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