Sec. 73.317  FM transmission system requirements.

    (a) FM broadcast stations employing transmitters authorized after 
January 1, 1960, must maintain the bandwidth occupied by their emissions 
in accordance with the specification detailed below. FM broadcast 
stations employing transmitters installed or type accepted before 
January 1, 1960, must achieve the highest degree of compliance with 
these specifications practicable with their existing equipment. In 
either case, should harmful interference to other authorized stations 
occur, the licensee shall correct the problem promptly or cease 
operation.
    (b) Any emission appearing on a frequency removed from the carrier 
by between 120 kHz and 240 kHz inclusive must be attenuated at least 25 
dB below the level of the unmodulated carrier. Compliance with this 
requirement will be deemed to show the occupied bandwidth to be 240 kHz 
or less.
    (c) Any emission appearing on a frequency removed from the carrier 
by more than 240 kHz and up to and including 600 kHz must be attenuated 
at least 35 dB below the level of the unmodulated carrier.
    (d) Any emission appearing on a frequency removed from the carrier 
by more than 600 kHz must be attenuated at least 43 + 10 
Log10 (Power, in watts) dB below the level of the unmodulated 
carrier, or 80 dB, whichever is the lesser attenuation.
    (e) Preemphasis shall not be greater than the impedance-frequency 
characteristics of a series inductance resistance network having a time 
constant of 75 microseconds. (See upper curve of Figure 2 of 
Sec. 73.333.)

[51 1997 FR 17028 , May 8, 1986]