[amsat-bb] Re: Eagle efficiencies
nx7u at arrl.net
Sat Sep 9 22:25:25 PDT 2006
Certainly that's true. But I would say "for a given size" is a quite valid
means of comparison. How many of us are truly unencumbered on antenna
size? It all boils down to what you can squeeze out of your "given size".
At 21:25 2006-09-09, Gary \"Joe\" Mayfield wrote:
>At some point (not that high in frequency) the beamwidths get so narrow
>the antennas are hard to point. Both on the satellite and on the
>ground. I don't think a spot beam would be popular with those living
>outside the spot. *for a given size* is a biased measurement.
>----- Original Message ----- From: "Scott Townley" <nx7u at arrl.net>
>To: "Amsat BB" <amsat-bb at amsat.org>
>Sent: Saturday, September 09, 2006 2:04 PM
>Subject: [amsat-bb] Re: Eagle efficiencies
>>Clarification, or more fuel to the fire...
>>For a *fixed overall physical size (aperture)*, antenna gain is
>>proportional to f^2
>>Pathloss is proportional to 1/f^2
>>So then the total link budget actually *increases* with increasing
>>frequency (f^2*f^2/f^2=f^2), since you have an antenna at both ends,
>>subject to the assumption stated initially.
>>There are several 2nd-order terms to consider overall, such as decreasing
>>transmitter power as frequency increases, thermal/galactic noise variations
>>with freq, etc., but *for a given size* higher is better.
>>Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
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