Sec. 73.766  Modulation and bandwidth.

    The percentage of modulation shall be maintained as high as possible 
consistent with good quality of transmission and good broadcast 
practice. In no case shall it exceed 100 percent on positive or negative 
peaks of frequent recurrence. It should not be less than 85 percent on 
peaks of frequent recurrence. The range of modulation frequencies shall 
be so controlled that the authorized bandwidth of the emission shall not 
be exceeded under all conditions of modulation. The highest modulating 
frequency shall not exceed 5 kHz.

[ 38 FR 18896 , July 16, 1973]