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Re: AO-40 data mode



> As I was listening to AO-40 the other day I wondered if it would be
> feasable to send voice as highly compressed data in order to achieve
> better S/N than with SSB phone....

In commercial satcom, this is the norm. Iridium, Inmarsat, etc. all take
advantage of digital modulation with some level of FEC to reduce the C/N
(S/N) requirements. Good examples of ham radio applications that achieve the
same results are PSK31 and AO-40 telemetry with FEC.  Using BPSK or maybe
MSK with FEC (forward error correction) would produce many more usable QSO's
on AO-40 and maybe eliminate LEILA from our ears.

Does anyone who is knowledgeable on the details of soundcard based DSP think
it is possible to do full duplex voice compression AND
modulation/demodulation using a sound card?  Would it be better to offload
some of the work to external hardware i.e. a PSK-1 type modem that accepts
encoded data from a PC on a serial port?

This is definnitely a discussion whose time has come. I agree that the
choice of codec is relatively unimportant as long as it is a public domain
algorithm.

Howie AB2S

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