How does multiplexing differ from FM signals to AM signals. If both FM and AM shift the message signal in frequency, then is there a difference between multiplexing for FM or AM signal?
In U.S. broadcast FM, the various subcarriers (pilot tone, stereo L-R, RDS, etc.) are modulated into the upper sidebands (above the 15 kHz L+R/mono audio, but below 100 kHz, for instance 38 kHz DSB for the stereo subcarrier) of the baseband signal before that entire multiplex is used to wideband frequency modulate a single, much higher frequency, FM carrier.
The FM carrier is modulated, but not shifted in center frequency.