"clifto" wrote in message
...
Has anyone gotten a good oscilloscope look at the type of signals
that distort by cancellation of part of the carrier, i.e. the
signals that synchronous detectors detect much better than other
types? I'm wondering about the characteristics that make these
signals so hard to understand when they "fade" into that condition.

--
All relevant people are pertinent.
All rude people are impertinent.
Therefore, no rude people are relevant.
-- Solomon W. Golomb

Not sure just what you mean, but AM needs a carrier to work. In an envelope
detector, the carrier is needed to have the correct waveform so that the
audio can be extracted. If there is no carrier, or too little, the waveform
is not what is needed for the detector to work. Listen on a sideband
receiver and you don't need the carrier and only the fade occurs with no
distortion.
Just look at the waveforms for AM and Single sideband in tutorials which are
all over the web and it is obvious. If the carrier goes down, you don't get
that waveform. I couldn't find any good papers on the web showing the
waveforms of AM and what happens as you reduce the carrier, but,...
Here are some references that may help you.
http://www.st-andrews.ac.uk/~www_pa/...rt9/page2.html
http://www.radio-electronics.com/inf...t/sync_det.php
http://www.radio-electronics.com/inf...e_am_demod.php
Compare the waveforms in those with what is here.
See Fig 1 in this paper. http://www.scott-inc.com/ham/ssb_im.pdf It is
what you see when the carrier fades compared to the classical waveform you
see for AM above. Note the nice sine wave is gone.


73, Steve, K9DCI