Michael Dunn ) writes:

-I'm still having a hard time figuring out AFC. I can see how I might
do it with a PLL - the DC error voltage being used to pull the LO to
the correct frequency. How was it done in the old days? ;-) If I
could design not only AFC, but also automatic tuning of an RF
preselector and perhaps even an antenna tuner, that would be tres cool.


Michael,
Get a copy of the "Radio Designer's Handbook" by F. Langford-Smith. It's
all about tube technology but pages 1150-1160 in the 1953 edition
(revised '67) give a very good explanation of AFC and how it was done then.

Good luck and have fun.
.... Martin VE3OAT