[R-390] Synchronous AM Reception

[John Kolb]

On Fri, 22 Mar 2002, Jim Brannigan wrote:

> Hello,
> What is synchronous detection and how is it different from zero beating the
> BFO against the carrier?

Sync detection is mainly for AM or DSB, not for SSB. With sync
detection, the supplied BFO signal is phase locked to be exactly
in phase with where the carrier should be. During selective
fading, or with DSB, the carrier is weak, missing,or phase
shifted from where it should be. With the BFO in phase with
where the carrier should be, the highest possible audio output
results. If the BFO is 90 degrees out of phase with the
carrier, cancelation occurs and no signal is heard. That's
the deep fades in the audio you get with the BFO on when
receiving an AM station, and almost but not quite zero beat.

John