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Re: Geosynchronous Satellites



On Tue, Dec 26, 2000 at 09:55:39AM -0600, Jon Ogden wrote:
> When I speak of analog signals, I mean a signal that is a voice modulated
> signal.  So SSB, AM or FM voice would all be analog signals.  So analog FM
> is standard FM voice or other audio (music as is the case for broadcasters).
> 
> Digital forms of modulation are things such as BPSK, PSK, MSK, FSK, AFSK,
> GMSK, etc.  In it you are applying a data stream to the carrier wave and
> modulating that carrier wave according to the pattern.  There are many, many
> additional forms of modulation that haven't even made it into ham radio: QAM
> (Quadrature Amplitude Modulation - A digital AM signal), pi/4 DQPSK, etc.
> In the cell phone world TDMA, GSM and CDMA all use digital forms of
> modulation.  In ham radio, RUDAK on AO-40 would be used for digital
> communication via the satellite.

I'm well aware of what forms of modulation there are for digital signals.
I just found the terms "digital AM" and "digital FM" rather unfamiliar
and actually rather odd.

Are there other forms of amplitude modulation for digital signals
besides QRM? I'd think those modes would be at a disadvantage compared
to the frequency/phase shifting modes with constant envelope.


73
Hamish
-- 
Hamish Moffatt VK3SB <hamish@debian.org> <hamish@cloud.net.au>
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