SSB CW?

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From: John F. Woods (jfw@ksr.com)
Date: Thu May 05 1994 - 15:59:23 EDT


So, while I've been discussing CW sidebands in email, I mentioned the
theoretical possibility of sending "single-sideband CW", i.e. strip off
the unwanted sideband and carrier and send only the information-laden
sideband (this is not the same as using an audio CW tone to modulate an
SSB rig; that is simply using the SSB rig as a mixer to shift the carrier
from AF to RF).

So now I wonder, has this ever been done? The filtering requirements
would be fiendish (unless perhaps the SSB generation was done at AF),
and a phasing approach would probably be awfully difficult, too. Maybe
an audio-range SSB CW signal could be practically generated using DSP
(to avoid having to construct unrealizable filters), and then shifted
to RF with a standard SSB rig. Demodulation would probably be tricky;
unlike AM CW, where you're just heterodyning, here you'd have to
actually re-insert the real carrier before you'd be able to recover
the modulation, and the margin of error is proportionately reduced: if
tens of hertz are sufficient to screw up voice, tenths of hertz
would... gee, what would the CW equivalent of "Donald Duck" sound like?

All the cost of SSB, but none of the benefits. Wait, are there any
benefits to phone? ;-)

I don't have any DSP hardware as such, but I can probably find a way
to play data streams if I toy around with this, to at least find out
what it sounds like. Maybe I will.

73, John, WB7EEL/1


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