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[TenTec] Slightly OT: SSB vs AM

To: <tentec@contesting.com>
Subject: [TenTec] Slightly OT: SSB vs AM
From: mark@microenh.com (Mark Erbaugh)
Date: Tue Apr 22 11:43:12 2003
This is sort of related to the discussion on the list of late about HiFi

I understand at a basic level the reason for improved performance of SSB
over AM, i.e. only one sideband and no carrier.  My question is: Compared to
SSB, is the energy in the other sideband and carrier truly 'wasted' or does
it convey some intelligence or noise immunity?  If it is wasted, it seems
that we are somehow violating Nyquist's rule. We have that same data rate
with half the band width and 1/4 the power. If that truly is the case, is
there the possiblity of another way further reduce bandwith and power and
keep the same data rate (short of digital encoding)?

Could some sort of frequency 'compression' be used. Assume that the audio
signal is 300 to 3000 Hz. Each frequency component in the signal would be
represented by a similar component, but at half the frequency difference
from 300 Hz. For example, the 300 Hz component would still be at 300 Hz, but
the 350 Hz component would be at 325 Hz, the 400 Hz component and 450 Hz,
and the 3000 Hz component at 1750 Hz (( 3000 - 300 ) / 2 + 300 ). The new
bandwidth would now be 300 - 1750 Hz. On the receiving end each frequency
component would be 'un-compressed' to 300 - 3000 Hz.


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