[amsat-bb] Re: All Satellites (Alan P. Biddle)

John B. Stephensen kd6ozh at comcast.net
Mon Sep 28 08:19:28 PDT 2009

FDMDV uses a 1400 bps codec, occupies only 1100 Hz and operates with any SSB 
transceiver. Comunications doesn't have to be full duplex. At 12-16 kbps the 
satellite and ground stations could alternate with short bursts of voice or 
text. This wouldn't fit in a 2.4 kHz SSB bandwidth but would require a 16-20 
kHz wide filter or use of a transverter and a simple SDR radio like the 



----- Original Message ----- 
From: "Gordon JC Pearce" <gordonjcp at gjcp.net>
>> KD6OZH's mentioning of a 1200 bps voice codec is very interesting,
>> too. I see that DSTAR's AMBE is down to 2000  with error correction,
>> and Speex operates down to 2000, too, though I think without error
>> correction. (I find the latter much more engaging as a ham, since it
>> is open source.) It would be a hoot to do a voice conference over the
>> Internet using a sample of low bitrate codecs and just get a sense of
>> what might be possible. One downside of voice is that it would occupy
>> the transponder far more than messaging, and Bob's favorable power
>> calculations would need to be estimated downwards.
> Would the packet satellite be capable of bent-pipe operation though?
> You'd need to transmit and receive simultaneously to get that working.
> I'd far prefer to use Speex rather than the locked-down proprietary AMBE
> codecs.

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