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Re: PSK-31 Satellite Donwlink Opportunity?






>From: Bob Bruninga <bruninga@usna.edu>
>To: ka1lm@AMSAT.Org
>CC: MCGWIER ROBERT <rwmcgwier@home.com>, digitalradio@yahoogroups.com,   
>carcomm@egroups.com, psk31@bipt106.bi.ehu.es, amsat-bb@AMSAT.Org
>Subject: Re: [amsat-bb] PSK-31 Satellite Donwlink Opportunity?
>Date: Sun, 25 Feb 2001 22:41:27 -0500 (EST)
>
>Yes, by making the UPLINK FM receiver have a widebandwidth of say 40 KHz,
>then even +/- 10 KHz of normal UHF doppler stays in the passband.  THus
>the recovered audio is unaffected by uplink doppler.  THis audio then
>simply goes into a normal 3 KHz SSB downlink.
>
>Again, this is only a quick-demo way of getting a low doppler multi-stream
>PSK-31 downlink to "test the waters".  THe ultimate objective for the
>"next" satellite would be the INBAND-INVERTING transponder so that then
>you can have 20 independent uplink QSO's... with only 45 HZ total
>doppler...
>
>I have posted the design of the INBAND-INVERTING transponder on
>http://web.usna.navy.mil/~bruninga/photos/PSKSAT.jpg
>
>Problem is, I havent figured out how much isolation I can get in such a
>tiny space... yet...
>
>bob
>

Bob.  do you know how they did it on Oscar III?  AS I recall that was an 
"inband transponder" and I think "worked" OK (although I clearly dont ahve 
any first hand information on that).

Tethers (carpenter rule) sounds pretty doable...

Robert
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