Earl Kiosterud wrote:

Synchronous AM demodulation uses a locally regenerated carrier, fed along with the AM signal
(upper or lower set of sidebands) to a multiplier (modulator). The result is the audio. It
replaces the envelope (diode) detector usually used. You can think of it as another superhet
stage where the result, instead of another IF frequency, is the baseband audio. That's
because the local oscillator is the same frequency as the carrier of the (IF) signal, so the
difference is zero. The sidebands wind up translated to baseband audio instead of to
another IF frequency.

There are advantages. Since one set of sidebands or the other can be used, if there's a
distant station 10KHz away, causing that AM whistle, you just switch to the other set of
sidebands, whichever comes in the cleanest. Also, it doesn't depend on proper amplitude and
phase of both sets of sidebands to work properly, as does the regular envelope detector, so
it works better with impaired signals.



I only understood about 75% of what your wrote, but if I understand
your meaning, this new receiving technique would not improve the sound
(it would still be limited from 100-6000 hertz), but would only reduce
interference.