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.
73, Joe
----- Original Message ----- From: "Scott Townley" nx7u@arrl.net To: "Amsat BB" amsat-bb@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.
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