> I understand that the purpose of SSB was to minimize the bandwidth, increase
efficiency, and pass only the necessary voice bandwidth for communications.
After researching the subject matter from QST issues during the '40s and '50s,
I have concluded that SSB was developed as a mode
which would offer greater articulation of communications through:
1) A reduction in transmitted power for a commensurate level of intelligibility
compared with that of AM;
2) A reduction in equipment weight;
3) A reduction in power supply capacity and loading (owing to a lower overall
duty-cycle);
4) A reduction in transmitted bandwidth without necessarily compromising
transmitted fidelity;
5) The elimination of an unnecessary redundant sideband; and
6) The elimination of an unnecessary "power hungry" carrier.
A note concerning point #4 above: The fact that SSB transmitted audio bandwidth
has been relatively restricted during the past forty
years without an emphasis on low-frequency energy, is due to limitations in
crystal filter technology: in order to achieve
reasonable alternate sideband rejection, the carrier set point must necessarily
be placed in a region which compromises low
frequency energy.
While the "phasing" method of eliminating the opposite sideband first appeared
as a solution, maintaining good carrier suppression
and alternate sideband rejection became a problem with temperature and
mechanical changes and deterioration. It wasn't until the
advent of DSP technology that better fidelity could be reasonably transmitted.
If DSP techniques were available in the '40s and
'50s, the overall audio quality and bandwidth we hear on the bands today would
be much different.
-Paul, W9AC
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