On Fri, 23 Feb 2007 21:20:11 -0600, craigm wrote
in :

Without details on the internals of the Sony IC, I don't know.

You'll find some information on the Sony ICF-2010 sync circuit he

http://user.netonecom.net/~swordman/...tWaveRadio.htm
An 8-page article called "Synchronous Detection of AM Signals:
What is it and how does it work?" appeared in the September, 1992
QEX magazine. It has several pages of the theory of amplitude
modulation and then goes into the demodulation. The circuit uses
the Sony CX-857 stereo decoder and PSN phasing amplifier chips
that are used in the "famous" Sony ICF-2010 synchronous detector.
The author of the article, Mike Gruber WA1SVF, an ARRL Laboratory
EMC/RFI Engineer, reports that Steve Johnston, WD8DAS sells a kit
for building it and has more information on his web site at
http://www.qsl.net/wd8das/syncinfo.txt. WD8DAS also has a copy of
a 2-page review from the October, 1994 issue of Electric Radio
magazine. I have received permission from the ARRL to post a
scanned copy of the article.

Reprinted with permission from September 1992 QEX; copyright ARRL.
Here's the link QEX 09/1992. (99k)