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Re: PSK-31 Satellite Donwlink Opportunity?



Actually the pilot tone idea is a good one.  Come up with a modified PSK31 
that places a pilot carrier say 100 Hz away from the data carrier, lock to 
that.  I mentioned that idea to someone once with respect to using PSK31 
with Aurora (the phase shift of a signal through Aurora kills PSK31, but if 
the reference was shifted by the same amount of phase...), but personally I 
have no experience coding DSP, so nothing happened with that.  But to be 
effective, I'd imagine that all stations would have to transmit that carrier 
as well.  But maybe not with the "in-band inverting" concept.

Also, I think the tether idea could work, but it would probably have to be 
several yards, not a few-- 1 wavelength is 10m or roughly 30 feet at 10m!  
Anyway the idea is very interesting indeed, as at higher frequencies, the 
tether seperation would have to be less and less-- making this idea for 
in-band satellites possible.

Fred W0FMS


>From: Dquagliana@aol.com
>To: amsat-bb@AMSAT.Org
>CC: bruninga@usna.edu
>Subject: Re: [amsat-bb] PSK-31 Satellite Donwlink Opportunity?
>Date: Mon, 26 Feb 2001 08:09:01 EST
>
>In a message dated 01-02-26 00:57:25 EST, you write:
>
>Fred writes:
> >  Doppler is a problem with PSK31, but maybe we can have a slightly
>widerband
> >  PSK that can tolerate some doppler--
>
>Re: doppler shift. It should be easy to generate a simple carrier
>within the audio bandpass that can be used on the ground to
>track the doppler.
>
>There would only have to be one reference carrier for all the signals,
>since they could all use it to track doppler and just keep track of how
>far away their signal is from the reference carrier.
>
>Software on the ground can look for the reference carrier and then factor
>out the doppler for all signals in the bandpass.  Or, did I miss something
>here?
>
>Re: Antenna isolation -- would it be possible to switch the antenna
>between transmitter and receiver at a very high rate (a kilohertz) ?
>The data bits are only being sent at 31 baud.
>
>Douglas KA2UPW
>dquagliana@aol.com
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