Synchronous vs. envelope detectors for use with forward acting AGC

It has been shown that Forward Acting Automatic Gain Control (FAAGC) is able to suppress the intermodulation (IM) products caused by rapid fading, particularly in the case of single sideband (SSB) transmission at UHF. Envelope detectors were used for simplicity, but since typical existing SSB systems use synchronous (or homodyne) detectors and a regenerated carrier, comparative analyses and tests with these detectors have now been made. It turns out that with synchronous detectors, little or no IM suppression is available, therefore, if FAAGC is to be used in a partially suppressed carrier SSB system, it is recommended that the carrier be enhanced at the receiver so that envelope detectors can still be used.