Sec.  73.1540   Carrier frequency measurements.

   (a) The carrier frequency of each AM and FM station and the visual carrier
   frequency  and the difference between the visual carrier and the aural
   carrier or center frequency of each TV and Class A TV station shall be
   measured  or  determined as often as necessary to ensure that they are
   maintained within the prescribed tolerances.

   (b) In measuring the carrier frequency, the licensee may use any method or
   procedure  that has sufficient precision to establish that the carrier
   frequency is within the prescribed departure limits.

   (c) The primary standard of frequency for radio frequency measurements is
   the standard frequency maintained by the National Bureau of Standards or the
   standard signals of Stations WWV, WWVB, and WWVH of the National Bureau of
   Standards.

   [ 43 FR 32783 , July 28, 1978, as amended at  48 FR 44805 , Sept. 30, 1983;  65 FR 30004 , May 10, 2000]