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Re: Re: Digital Voice Via Satellite



>protocol development stage, and a major stumbling block seems to be 
>getting digital voice data to fit in a SSB-type channel.  There was an 

Why does digital voice have to fit in a SSB bandwidth? This is
especially counterproductive on an amateur microwave satellite where
bandwidth is much more plentiful than power.

Even on HF, there are some very good reasons to go *wider*, not
narrower.  The right wideband signal design can be considerably more
resistant to interference and frequency-selective fading. And because
you can use less transmitter power overall, you cause less QRM to
others.

K0VTY asked about digital voice in a DX pileup, implying that it would
have to be worse than SSB. But imagine a modulation mode where you
could actually separate and demodulate each individual transmission in
a pileup of stations all transmitting to you in an uncontrolled
fashion on the same frequency at the same time.

Such a mode actually exists! It's called spread spectrum, and that's
exactly how CDMA cellular base stations operate.

For human factors reasons this mode might be better suited to textual
communications than to voice. With text, it's easy for the user
interface to display all the messages together for the operator, e.g.,
one per line or one per window. With voice, the system would probably
have to store and play back the demodulated transmissions one at a
time.

Phil



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