Sec. 101.811  Modulation requirements.

    (a) The use of modulating frequencies higher than 3000 hertz for 
single channel radiotelephony or tone signaling on frequencies below 500 
MHz is not authorized.
    (b) When amplitude modulation is used, the modulation percentage 
must be sufficient to provide efficient communication and must normally 
be maintained above 70 percent on positive peaks, but may not exceed 100 
percent on negative peaks.
    (c) When phase or frequency modulation is used for single channel 
radiotelephony on frequencies below 500 MHz, the deviation arising from 
modulation may not exceed plus or minus 15 kHz from the unmodulated 
carrier.
    (d) Each unmultiplexed radiotelephone transmitter having more than 3 
watts plate power input to the final radio frequency stage and initially 
installed at the station in this service after September 4, 1956, must 
be provided with a device that will automatically prevent modulation in 
excess of that specified in paragraphs (b) and (c) of this section which 
may be caused by greater than normal audio level.