At 11:38 AM 04/22/2003 -0500, Jerry wrote:
The voice spectrum has two major groups, one at a few hundred Hz and
another out maybe three times that frequency with a gap in between.
There was a proposed scheme in the ARRL handbook a few years back to
separate those with separate bandpass filters, then heterodyne the upper
one into the gap at the transmitter, then shift it back to its normal
range in the receiver. Saved at least a third of the spectrum, maybe
more, but it went over like a lead balloon.
There was a commercial unit made, think it was called
NBVM (narrow band voice modulation) or something similar.
It comes to me that Henry radio produced it, or sold it..... (?)
......and Jerry was right. It was a bust! Probably because it
sounded bad when listening on standard receivers....
w8au
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