RE: [amsat-bb] Fwd: Transponder ideas for future satellites

["Tom Clark" <tac@xxxxxxxxx>]

Peter -- I don't think it is practical. You hit on the reason in your
note:

> [snip]
> Some of the cons might be:
> 1. Signal is relatively wide and might require more power to get
> decent SINAD.

The problem lies in the demodulation of the FM'd signal to recover the
baseband signal. FM requires much larger S/N -- with the penalty being
in the 15-20 dB range. This in turn means that you would need:

either (1) a big solar array and a big PA on the spacecraft,
and/or (2) 15-20 dB of antenna gain accompanied by precision attitude
stabilization at the spacecraft,
and/or (3) All the users have to buy (and point) 10ish meter dishes on
the ground.

Sorry, but the laws of physics win again! -- 73 de Tom, W3IWI

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