"Brenda Ann" wrote in message
...

Why would you want a bandpass less than that of the deviation used? FM
broadcast deviation is 75 KHz each side of the carrier center frequency,
for
a total bandwidth used of 150 KHz. A 110 KHz bandwidth filter would cause
massive distortion. Mono and stereo FM broadcast signals use the same
bandwidth.

However deviation and bandwidth are not the same thing. From Frequency
Modulation Theory:
http://hyperphysics.phy-astr.gsu.edu...dio/radio.html

Amplitude Modulation bandwidth can be considered exactly two times the
highest frequency of modulation, while Frequency Modulation bandwidth is
described by Bessel Functions that extend much higher than those of
Amplitude Modulation. In fact the "FM Advantage" in signal-to-noise ratio
stems exactly from spreading the modulation over a greater bandwidth than
Amplitude Modulation.


BANDWIDTH = 2 X (PEAK DEVIATION + HIGHEST MODULATING FREQUENCY)