Satgen66  Pacsat Hardware and Software - Expensive or Cheap    by GM4IHJ

In the six months since launch, a great deal of information has emerged,
and although the packet satellite network is not yet operational, a clear
picture of hardware and software requirements is emerging. The standard "
black boxes bought off the shelf outfit ", seems to be :-
H1  a 2m FM transmitter modified for varactor drive by Tx data
H2  a 70cm multimode transceiver fitted with UP/Down frequency control AFC
    driven by the G3RUH BPSK modem or special software.
H3  a G3RUH BPSK Fuji type modem ( EG Paccom PSK-1 ), or , for FSK down  
    or ( for Uosat3) a G3RUH 9600 bps FSK modem
H4  a standard packet TNC which has its own modem bypassed
H5  a microcomputer ( IBM AT XT , Atari ST or Amiga or equivalent )
    running DOS 3.0 and Windows
H6  Az El computer controlled twin beams for 2m and 70cms, up in the clear
    on a mini tower with a Rx pre amp.

S1  Tracking and Prediction software for all the Packet satellites
S2  Special communications protocol and telemetry decode software
S3  Kansas City tracker or equivalent for Auto antenna control
S4  Doppler tuning program
All software to be "Terminate and Stay Resident" to allow concurrent usage
on a single microcomputer.

A check of user station reports on Fuji 20 JAS1-B will confirm the above.
This outfit is extremely expensive and cannot be assembled without some
DIY soldering , circuit modifying and connecting. Many stations get by
with far less sophistication, making equipment or modifying old equipment.
The following Low Budget alternatives are possible :-

Low Budget BPSK (Pacsat , Lusat, FO-20). Xtal control 2m FM Tx varactor
driven. 70cm converter to 28MHz SSB Rx hand tuned, prompted by RUH modem
meter/LEDs. G3RUH Fuji modem kit/PCB. Simple all round antennas. Comment -
Tuning is a very big problem, and simple antennas only work in good
conditions. This approach still requires microcomputer plus S1 and S2.

Low Budget 9600 Uosat3 FSK . Simple 2m FM Xtal controlled Tx modified for
varactor drive. Very simple 70 cm Rx using converter to 28MHz FM Rx or
27MHz CB , Rx modified for Rx data out of discriminator. G3RUH 9600 modem
or Kit/PCB. Simple fixed all round antennas.  Comment - Uosat3 has AFC on
its uplink so access easier. Downlink is strong and only needs tuning
every 3KHz of doppler. But please note that reception of 9600 bps takes
practice. It is not easy first time.

If we all need the full expensive outfit ,packet satellites will be
relegated to a rich man's sport. If however Radio Amateurs can devise
cheap alternatives as is already happening with Uosat3 9600 FSK, then
everone can join in. Uosat3 is a particularly good target for the
ShortWave Listener/ Packetsat receive only station using cheap DIY
hardware but remember you still need the protocol software. Dove the
easiest target of all on 145.825MHz via a simple terrestrial packet
station ,is presently non operational awaiting repair. 73 de John GM4IHJ @
GB7MAC  2nd July 90.