SATGEN59  The Paccom PSK-1, and, Tracking Problems  By GM4IHJ 15 May 90

PSK-1   A first look at this commercial Fuji type Pacsat modem suggests 
that its makers have tried to allow for most of the problems. It will send
/ receive satellite 1200 bps FSK and BPSK, and, terrestrial VHF BPSK FSK,
plus receive 400 bps downlinks from AO10 and AO13. It supports several
modes of auto frequency control to allow for satellite doppler, and it has
a host of new features, such as Digital Signal Processing algorithms and
wide range AGC , which are said to improve reception. It is neatly
packaged and should do an excellent job for those already familiar with
BPSK reception.Those unfamiliar with BPSK may find it a problem at first
It cannot receive Uosat3 9600bps FSK, and it does require a separate TNC.
It also requires that you modify your 2m Tx , feeding Tx Audio direct to
its varactor.First results setting up the PSK-1 suggest that it will give
a lot of initial frustration.It is not easy, and it does not like laptops,
Macintosh commands, or old TNCs. It is also doubtful whether users will
want , or be able to afford, the additional Kansas City Tuner and Tracker
recommended for use with it. However if you are using a 70cm transceiver
you have RUH AFC and do not need the Tuner. If you have tracking software
printout of doppler tuning , you should not need the Tracker. I look
forward to comparing commercial BPSK performance with all expensive aids
available,versus,DIY modem and 9600 FSK. The latter clearly outperforms
DIY BPSK, and probably still outperforms the commercial BPSK.

More on Doppler Tracking    Have several complaints about poor Keplerian
Elements being further confused, because Jamsat Epochs may not mean same
thing as NASA/NORAD Epoch. Yes available Keps are not always perfect , but
if you use doppler tracking this should not matter, too much. Either your
Rx locks to signal , via AFC for BPSK. Or, via centre tuning for FSK. This
tells you direction sat sig is coming from at any moment. Provided your
software is checked against exact point of closest approach when doppler
rate of change in KHz per minute is at its highest, you can measure exact
frequency your Rx AFC locks to, or, centre meter tunes to at point of
closest approach of the satellite. My ICOM 451 frequencies at cpa lock are
Uosat3 435070.5 Khz, Pacsat 437026.5 KHz, Lusat 437151.0 KHz and JAS1-B
435910.5 KHz.NOTE, these are not sat Tx operating frequencies, they are
what my rx tunes at sat cpa of BPSK 1500 Hz or FSK carrier (my MM coverter
to R2000 and, MM transverter to R2000 see Uosat3 ,3.8 and 1.2 KHz higher
respectively). My software adds calculated doppler to the above Eg -:
   UOSAT3 OSCAR 14 on 12 / 5 / 90 via ICOM 451
   UTC   AZ   EL   Lat   Long   SigF + Dop KHz
   0952  52   12    63    331    435076.1     WHATEVER THE TIME UTC. IF
   0953  63   15    59    334    435074.7     FREQUENCY READOUT ON LOCKED
   0954  76   17    56    336    435073       SIGNAL SAYS 435074.7 , I
   0955  90   17    53    338    435070.9     PUT ANTENNA 63/15 .When
frequency readout approaches 435073 I move antenna to 76/17 .I ignore the
time and use what the doppler is telling me , to track the satellite

STOP PRESS FO20 is back on BBS but Tx sometimes goes off briefly for a few
seconds. Pacsat, Lusat , Uosat3 all loading software. No sign of Dove.
73 de John GM4IHJ@GB7MAC 15 May 1990.