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#19
May 18th 04, 11:30 AM
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Dan Richardson wrote in message . ..
On Mon, 17 May 2004 10:42:49 -0500, (Richard Harrison) wrote: [snip] Power varies as the square of the voltage. One can see the difference in the field strength is hardly worth the effort for an amateur to try to increase the length of his antenna. It`s about a 3 dB gain from 1/4-wave to 5/8 wave. [snip] The 3 dB gain figure is valid when mounted on theoretical perfect ground. For a ground-plane elevated above real ground you'll find the gain to be rarely greater than 1 dB. Dunno. My real world tests don't quite agree. In using 30 mile ground wave tests across town, I tested 1/4 GP's, 1/2 waves including decoupling sections, and a 5/8 GP with 3/4 wave radials. All at 36 ft. The 5/8 ate the 1/4 GP for lunch. Probably 2 plus S units better than the 1/4 GP. The 5/8 beat the 1/2 wave by 1.5 S units. And this was tested and repeated over a period of months. Never varied. Ground wave testing is quite stable, and accurate for those low angles involved. Much more accurate than trying to compare using constantly varying skywaves. In real world gains, thats more than 1 db. 5/8 antennas are weird animals. On 2m, they suck. On HF, they can do fairly well, cuz the angles involved are not as critical. I used a 5/8 GP on 17m for 2-3 years. "also at 36 ft at the base". It mangled every other antenna I had on that band. On 10m, the 5/8 beat any other length radiator quite handily. Again, on the critical 2m band, peeeyooooo.....they stink. BTW, on skywave, using a quick A/B test, all preferred the 5/8, over the other antennas. So it wasn't a low angle ground wave fluke. MK |
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