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RE: Re: Digital Voice Via Satellite



> I don't think the technology is quite to that point yet.  ;-)  My 
> impression of digital voice on the ham bands is that we're at the 
> protocol development stage, and a major stumbling block seems to be 
> getting digital voice data to fit in a SSB-type channel.

It can be done.  The problem is that the only way ATM is to use a proprietry
vocoder (AMBE) to compress the voice down to 2.4 kbps or less.  

That at least tells that getting digital voice into an SSB bandwidth is
quite possible.  Just that someone needs to reinvent the wheel a little, if
we don't want to be dependent on proprietry technology.

One reason to go down this road is to allow us to exploit the potential of
modern computer power and do as much of the work as possible in software.
  
> There was an 
> interesting related article on PTC, which seems to be a promising 
> technology to help with voice data compression, but I don't think 
> anyone's gotten a digital voice "TNC" type box going yet.  
> (My info may 
> well be out of date, though..)

There is the UK ham who built a digital voice system that uses the AMBE
vocoder and runs at 2.4 kbps (3.6 kbps with FEC).  His modem was a 36 tone
multi carrier modem (with QPSK on the individual carriers), IIRC.
Signalling rate was 50 baud.

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