[TowerTalk] More from the M2 antennas quality control file
normanlizeth at gmail.com
Mon Apr 13 10:33:05 EDT 2015
Thanks! I do understand. This makes the math a lot clearer.
Regarding the orbiting signal generators, if the spacecraft is in LEO,
then the accuracy of the tracking becomes "noise" on the measurement?
Are there any spacecraft that you could suggest?
On Mon, Apr 13, 2015 at 10:25 AM, Jim Lux <jimlux at earthlink.net> wrote:
> 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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