[rfeenstra]

Okay all of you FM gurus, I confess lot a lot of ignorance on FM discriminator technology (and a lot of AM stuff too!).  On weaker stations, I get a bit of 120 cycle hum when tuned slightly off.  As tuning is brought in precisely, the hum diminishes until virtually gone at one precise dial setting.  Is this typical of  discriminator operation?  Where does the hum come from?  Do I have an alignment problem?  When doing the alignment, it was interesting to watch the DC offset at the output of the discriminator vary as tuning was adjusted.  I set the the discriminator for 0 volts DC when the signal level was the greatest as determined by the AGC signal.  Is it possible that the hum is coming in early in the system and the weak signal is not being fully limited to eliminate AM, and that when the discriminator is perfectly balanced in its tuning that the AM is cancelled out?  Just curious if I have a problem or if it is normal operation.