On 4/13/15 7:33 AM, Lizeth Norman wrote:
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?
I'd look for any of the numerous cubesats that are up. AMSAT probably
has a list somewhere on their website.
They're radiating in the ham band.. not at 432 (hopefully).
You point the antenna at a fixed position in the sky and let the
satellite cross through the beam and log the power. It will vary a lot
due to a variety of effects, but averaging over multiple passes, etc.
you can do pretty well.
On Mon, Apr 13, 2015 at 10:25 AM, Jim Lux <jimlux@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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