§ 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.

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