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re:Digital modes on Sats


About digital modes via satellites I have done many tests.
There are many kinds of digital modes that can be used via satellites.

I have done many RTTY and SSTV via the transponder satellite, but also 1200 
BPSK packet is possible only very dificult and with good up/dwn links. Other 
interresting and good working modes via transponders are PSK31 and 
hellschreiber. Some 1 or 2 years ago I was very active via AO10 with RTTY. 
Together with ON1DLL we did several tests and the result was that we needed 
100W PA power for a 60% understandable ssb voice contact, and when we 
switched to RTTY we could reduce power up to 5W PA power !!! with about 20% 
failures. With 10W it was about 5% failures. Digital made therefore can be 
very usefull with satellite communications when the link is not good enough 
for voice.

Packet radio via transponders is not very succesfull because of the relative 
low downlink signals, but via the FM satellites it is no problem. Even 9k6 
packet is no problem via the crowdy UO14 satellite when it is above europe. 
A full 9k6 packet connection to some other amateur will ofcourse interrupt 
other FM users, but with sending small UI frames you can send CQ's or small 
messages in a quiet moment.

There is much more possible with satellites than only making SSB/FM voice 
contacts, just try it out...

73 de PE1RAH, William

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