Hi folks,
I finally got the AM sync detector running. The hardest part
of it is the loop filter. I haven't been able to find any information on
loop filter design, when there is no divider in the feedback loop. I have
discovered that with a 4046, you set your lock range by setting the Fmin,
Fmax of your VCO, while the capture range is set by the loop filter. With a
wideband loop filter, the demodulated audio sounds fine, but with a + or -
3kHz capture range, there is a chirping type of distortion on the modulation
peaks. In this case, settling time is 50mSec, while with the broadband loop,
settling time is 100uSec.
Overall, these things aren't too bad to build, except for that loop filter.
Once I get that optimized, I will have a sync detector that is worthy of
being sold as a stand alone unit.
Projected price of this unit will be around the 100 dollar mark.

Pete