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[aprssig] PC2 PSK31 multiuser transponder

Robert Bruninga bruninga at usna.edu
Thu Aug 11 22:48:33 UTC 2005


I will generally not bother the APRSSIG list with
PCSAT2 announcements unless they directly
affect packet operation.   I will assume everyone
that is interested in it will be on the amsat-bb.
But here is one I think everyone should know 
about, since everyone has an FM rig and can
receive it.

>>> Robert Bruninga 08/11/05 6:45 PM >>>
There is another big advantage of the multi-user 
sharing PC2-PSK-31 transponder (with the FM 
downlink) compared to any previous linear trans-
ponder.  I was reminded of this by Peter Martinez, 
the father of PSK-31.

Power hogging was always the problem with linear 
transponders, but it will much less with this trans-
ponder because the entire downlink band is visible 
to all users.  Everyone sees exactly the same thing.

If your downlink signal is stronger than everyone 
else's, everyone else including you will see who is 
hogging the downlink AND you will see exactly your 
impact on everyone else's signal.  There will be no 
excuse for excessive power.

On a free-floater satelilte (RAFT is our next one),
this mode could be almost completely self leveling.  
But with all the blockage on ISS due to the huge 
structures, each station will see large variations in 
their signal and so it will take careful reaction to 
keep one's signal reasonably constant.

de Wb4APR, Bob






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