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RE: [aprssig] Re: RE: AO16/LO19 Uplink w ANY PC!



At 11:53 PM 9/19/99 -0400, Bob Bruninga wrote:
>On Sun, 19 Sep 1999 schoon@amgt.com wrote:
>
>> So, would it be safe to say that by replacing some filters with 20 khz
>> bandwidth and a decent preamp, one could forget about doppler??
>
>Not at all.  PSK demod of an SSB signal requires doppler tracking to say
>about 100 HZ.  THis is not an IF bandwidth issue, but a fact of PSK which 
>requires SSB reception.  There doppler is a 1hz-for-1hz offset in the
>desired tone for demodulation...

This is an artifact of the demodulator, not of PSK itself. It's
perfectly straightforward to make a PSK demodulator that tracks
Doppler automatically. PLLs and Costas Loops are both dead easy
to implement in either hardware or software at these bit rates.

References: any decent text on communications. I like Haykin (see
http://www.qsl.net/vaeldh/reading.html).

Laura Halliday VA3LDH   "Que les nuages soient notre pied
Grid: FN03gs                a terre..." - Hospital/Shafte
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