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Re: ECHO PSK-31 test report



Regarding future PSK-31 experiments on ECHO...

Tony,  KT2Q, suggested that we do the next PSK-31 
experiment on ECHO using mode J since that is where
the uplink receiver is optimized instead of 10m where
it isnt.

Actually, this might be worth considering...  Here are the
discussion points:

1)  This experiment's PRIME objective (as originally defined 
in the PCSAT2 and RAFT satellite designs) has always  been
to provide a MULTI-USER FDMA transponder to get away
from the limitations of an FM transponder and get back to 
a multi-user shared transponder...  PSK-31 was the obvious
choice (though CW is also possible)...
 
2) 10m is optimum because of the LOW doppler (1 Hz/s avg)
3)  2m uplink will have 5 to 15Hz/sec or so Doppler
4) NO EXISTING PSK-31 software can handle this (other than
    Peter Martines's custom code just for this application)
5) We need more experimentation, but understand that we
   are taking away a valuable AMSAT transponder for these
   tests
6)  Unless there is something else we dont know about, I think
     we have demonstrated the futility of the 10m uplink -OR-
     we need to get more people with 4 kW ERP on the air

THERFORE, I suggest maybe a new apprroach to consider:

Switch the "PSK-31" uplink to 3 KHz in the 2m band and 
continue the experiment:

1)  This lets Peter and other experts figure out, refine and get
some good hig-rate Doppler PSK-31  working...

2)  But so that we dont frustrate users, then we also allow
narrowband CW as well, at ONE ERP level ONLY.
This lets many more people participate on these days of 
the experiment until we get the PSK-31 stuff working..

*** But maybe this is counter productive.  If one high power
CW station gets on there and BLASTS the AGC, then he
not only destroys the downlinnk for eveyone else, but also
for the PSK-31 portion of the test as well...   And AMSATS
have a 100% track record of uncontrolled power on the
uplinks by uncareful operators.

PROCESS:  We will have to experiment with the UPLINK 
ERP to get it right.   And we do it like we did on PCsat, by
publishing IN ADVANCE an "Experimenters Agreement"
that must be read, understood and adhered to for
authorization to participate in the experiment:

1) ONLY OMNI verticals may be used on the Uplink
2) TX power must be limited to 5 Watts  
               *or*
3) Experimenters that know how to compute ERP
    may use any combination of antenna and TX
    power to arrive at 10 Watts ERP

4) All experimenteers must watch a "waterfall display"
   of the dowlink spectrum to avoid operating near
   the freeucny of the PSK-31 experimenters.  CW
   operators must remain below 1500 Hz and PSK-31
   users will try to stay above 1500 Hz.

If someone cannot adhere to these criteria, then they are not
authorized to transmit as part of this experiment.  After a 
few passes we will change the ERP requirement as 
needed to get the right power at the AGC of the receiver.

To handle the high rate Doppler on CW,  we can use
the venerable human brain for now.... but avoid hitting
the PSK31 users.  This is why watcing the "waterfall"
is mandatory...

Again, the purpose of the "PSK-31" experiment was to
give us a MULT-USER transponder on an FM satellite.
10m was the best way, but sub-optimum on this particular
satellite arrangement.  I think it might be time to try 
something different?

de Wb4APR, Bob
----
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