[NCARC] Local PSK31?

[James Cizek]

 James,
 
 PSK on Satellites? I never heard of that. PSK seems more an HF
 activity, especially on 20m. And aren't satellite transmissions FM?
 I've never tried modulating an FM signal with PSK. I have to think
 about that for a while.
 
 This seems interesting, can you provide a bibliography of articles
 that discuss PSK via satellites? I'm very curious about the Doppler
 shift effect on PSK signals.
 
 73, Rod N0RC
 
 


    There are a few satellites that have FM transponders.  AO27 is an 
   FM repeater, as well as UO14.  I think there may be one more.
   (And if anyone follows this, Amsat-Oscar 7, launched in 1974 just
    "came back alive" this weekend after 24 years of silence!!!)

   However, the majority of the analog sats are SSB transponders.  Most
   are inverting, meaning you transmit LSB on your uplink at one edge
   of the uplink transponder and you hear yourself on USB on the opposite
   edge of the downlink transponder. PSK31 is becoming very popular
   on the sats because it works so well in noisy and or marginal 
   signal levels which the sats can sometimes be!  Our newest bird, 
   Amsat-Oscar 40 is very a very popular sat to work PSK31 through
   as it is very stable, and has a very clear, easy to receive signal.
   The doppler can be a little wicked (especially since AO40 downlinks
   on 2.4 GHZ) but that is easily handled by the PC.  The sat program
   I use can tune the radio for you, or what i usually do is to tune
   the beacon on one radio while using another to transmit.  The computer
   listens to the beacon through the soundcard and tunes BOTH radios 
   an equal amount to keep the beacon centered.  This handles the doppler
   within about 2-3hz and is quite capable of keeping it in line for
   the PSK program to remain functional! 
   
   The satellite world is becoming wider and wider, popular modes on the 
   sats is now including packet, SSTV, PSK, Fast Scan TV, you name it. 
   Most of the modes that are available down here on earth are now being
   used a little bit on the sats too!

   -KI0KN  James