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Re: Doppler on LEO's.



Hi Phil,
         Point taken, you are of course correct. What I was thinking was 
that there must be quite a lot of people outside the USA who just can't 
afford to purchase such equipmet.

73 John.


>From: Phil Karn <karn@ka9q.net>
>To: john hackett <la2qaa@hotmail.com>
>CC: Amsat-bb@AMSAT.Org
>Subject: Re: [amsat-bb] Doppler on LEO's.
>Date: Sat, 08 May 2004 15:38:11 -0700
>
>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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