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Re: Doppler on LEO's.



john hackett wrote:

>
> Imagine PSK31 on mode-S.....(that's what we of the "rocks for brains" 
> brigade do).
> 
> The mind boggles!.

Not really. With the right ground station it would be easy. Just 
consider a digital receiver with a passband wide enough to accomodate 
the modulation bandwidth plus the full doppler spread from AOS to LOS. A 
tracking program would make an open-loop Doppler estimation for initial 
acquisition and a loop would track the carrier once it is found. The 
whole thing can easily be done in DSP on a modern general purpose computer.

It would be even easier with a more modern and efficient modulation 
format than PSK31. Consider that this job is already routinely done by 
the various satellite phones (Globalstar and Iridium).

Phil

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