[TowerTalk] More from the M2 antennas quality control file
jimlux at earthlink.net
Mon Apr 13 10:25:17 EDT 2015
On 4/13/15 6:42 AM, Lizeth Norman wrote:
> Do have a question. How does one characterize an unknown antenna's
> parameters? If I understand it correctly, to characterize the "real
> world performance" (using the sun) of this type of antenna, G/T needs
> to be known.
Some form of antenna range. Sun Noise works, sort of, but the problem
is that unless your antenna has a very narrow beamwidth, the sun is
"small".. The sun is 1/2 degree wide. If you have a 20 degree beamwidth
(20dBi gain), the sun occupies only 1/1600th of the field of view
(400^2) so even though the sun is, say, 5000K, it's swamped by the mass
of 3K cold sky around it. Get to a 30 dBi antenna with a 1-2 degree
beamwidth, and then sun noise starts to be a useful source.
There's a fair number of orbiting UHF sources these days, which provide
a decent far field point source (albeit not of calibrated signal
strength, but at least you could get good pattern cuts).
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