> The antenna, that I want to build, is described in a paper (probably 20 years old) > by Dick, WD4FAB, titled 'Antennas for microsat ground stations', and the paper > describes the large time, a LEO remains at low elevations - about 76 % below 20 degrees - > and then concludes, that this is fine for a J-Pole.
Absolutely true with respect to the*antenna pattern* but the current batch of LEO satelltes even though they are in the main beam of the omni antenna at the horizon, are -too-far-away- to be heard with only 2.1 dB of omni dipole antenna gain. So yes, those are good "satellite antennas" for omni coverage, but they wont hear anything that low because the satellites are 3000km away and the current crop of satliltes mostly operate in the 1/2 watt or less area. The only thing you will hear down to the horizon with these antetnnas is the ISS that is operating at 10 watts or more. You are better off simply giving up on the horizon (for an omni) and increasing your gain higher up. And a 1/4 wave whip over a ground screen will give you 5.1 dBi instead of 2.1 dBi. And then you may begin to hear things above about 15 degrees or so (and 3 dB better than you would hear on any antenna optimized for the horizon.. And it is even better to go to a 3/4 wave vertical over a ground screen and then you get almost 7 dBi gain starting around 30 degrees. You wont hear the low satellites (you can't anyway on an omni) but you will hear them much better when they do get above about 25 degrees... (but notice, this is less than 1/4th of all passes). _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
