Satgen151  The Packet Satellite Situation. A Personal View  GM4IHJ 16Feb92

Love them, or hate them, packet satellites are here to stay. Perhaps we
had it too easy at the start with Fuji 12. As a first of type it was a
marvelous introduction, and, despite its power and software problems, it
pointed the way forward to an interesting future.
It is always difficult in any developement program to know whether to
concentrate on, and, repeat what already works. Or, to take a further step
forward with each new satellite. Luckily for us both U of Surrey , and
Amsats NA/LU were building the next generation, and we got two types - the
present Pacsat 1200 baud Phase Shift Keying, and, the much faster Uosat
9600 baud FSK.
Two years on it is possible to evalute these very different approaches. I
started with my Fuji modem on Pacsat PSK and had no problems in its
digipeater mode. But as the problems of fitting and testing operational
software in these slow birds became apparent, I rapidly built a 9600 baud
RUH modem and switched to Uosat3 Oscar 14.
Yes it is necessary to modify your Rx and Tx to handle the wideband Uosat
keying, but as I regularly looked at Pacsat I discovered that I needed far
more mods there, removing Tx pre emphasis, then trying to combat the
flutter on the Pacsat phase shift, and last but not least attempting to
counter the scintillation problems which at my 56N latitude are far more
serious on 1200 PSK than they are on 9600 FSK. Needless to say in face of
these problems I have been less than enchanted by Pacsat and Lusat,
Particular as I monitored traffic patterns and saw the better than 500%
improvement in traffic handling on the higher speeed FSK birds. ( Amsat NA
91 Colloqium papers please note - if you want to compare traffic handling
you need to compare BOTH percentage readability of reception AND TRAFFIC
DENSITY AND TRANSFER RATES).
Today in February 92 Uosat 3/5 are the clear winners. I therefore find
myself reading of all manner of Amsat groups building PSK sats with
distinct qualms for the future of Amateur Satellite packet. Uosat led ,the
packet satellite gateways have quietly revolutionised the flow rate of
international traffic. Indeed Uosat usage is reaching overload levels. In
my view the building of slow PSK Pacsat clones is a step backwards. As a
consequence of which we may lose yet another battle to improve Amateur
Radio generally through the medium of Amateur satellites. We failed with
our " Oscar 13 will be a new 24 hour 20 metre band", we have badly fumbled
the enormous educational impact of the simple Dove sat. Lets not slip up
in our efforts to provide a super internationl packet satellite facility.
73 de John GM4IHJ @ GB7SAN