Sec.  2.1055   Measurements required: Frequency stability.

   (a) The frequency stability shall be measured with variation of ambient
   temperature as follows:

   (1) From −30 ° to +50 ° centigrade for all equipment except that specified in
   paragraphs (a) (2) and (3) of this section.

   (2) From −20 ° to +50 ° centigrade for equipment to be licensed for use in the
   Maritime Services under part 80 of this chapter, except for Class A, B, and
   S Emergency Position Indicating Radiobeacons (EPIRBS), and equipment to be
   licensed for use above 952 MHz at operational fixed stations in all
   services, stations in the Local Television Transmission Service and
   Point-to-Point Microwave Radio Service under part 21 of this chapter,
   equipment licensed for use aboard aircraft in the Aviation Services under
   part 87 of this chapter, and equipment authorized for use in the Family
   Radio Service under part 95 of this chapter.

   (3) From 0 ° to +50 ° centigrade for equipment to be licensed for use in the
   Radio Broadcast Services under part 73 of this chapter.

   (b) Frequency measurements shall be made at the extremes of the specified
   temperature range and at intervals of not more than 10 ° centigrade through
   the range. A period of time sufficient to stabilize all of the components of
   the oscillator circuit at each temperature level shall be allowed prior to
   frequency measurement. The short term transient effects on the frequency of
   the transmitter due to keying (except for broadcast transmitters) and any
   heating element cycling normally occurring at each ambient temperature level
   also shall be shown. Only the portion or portions of the transmitter
   containing the frequency determining and stabilizing circuitry need be
   subjected to the temperature variation test.

   (c) In addition to all other requirements of this section, the following
   information is required for equipment incorporating heater type crystal
   oscillators to be used in mobile stations, for which type acceptance is
   first requested after March 25, 1974, except for battery powered, hand
   carried, portable equipment having less than 3 watts mean output power.

   (1) Measurement data showing variation in transmitter output frequency from
   a cold start and the elapsed time necessary for the frequency to stabilize
   within the applicable tolerance. Tests shall be made after temperature
   stabilization at each of the ambient temperature levels; the lower
   temperature limit, 0 ° centigrade and +30 ° centigrade with no primary power
   applied.

   (2) Beginning at each temperature level specified in paragraph (c)(1) of
   this section, the frequency shall be measured within one minute after
   application of primary power to the transmitter and at intervals of no more
   than one minute thereafter until ten minutes have elapsed or until
   sufficient measurements are obtained to indicate clearly that the frequency
   has stabilized within the applicable tolerance, whichever time period is
   greater. During each test, the ambient temperature shall not be allowed to
   rise more than 10 ° centigrade above the respective beginning ambient
   temperature level.

   (3) The elapsed time necessary for the frequency to stabilize within the
   applicable tolerance from each beginning ambient temperature level as
   determined from the tests specified in this paragraph shall be specified in
   the instruction book for the transmitter furnished to the user.

   (4) When it is impracticable to subject the complete transmitter to this
   test because of its physical dimensions or power rating, only its frequency
   determining and stabilizing portions need be tested.

   (d) The frequency stability shall be measured with variation of primary
   supply voltage as follows:

   (1) Vary primary supply voltage from 85 to 115 percent of the nominal value
   for other than hand carried battery equipment.

   (2) For hand carried, battery powered equipment, reduce primary supply
   voltage to the battery operating end point which shall be specified by the
   manufacturer.

   (3) The supply voltage shall be measured at the input to the cable normally
   provided with the equipment, or at the power supply terminals if cables are
   not normally provided. Effects on frequency of transmitter keying (except
   for broadcast transmitters) and any heating element cycling at the nominal
   supply voltage and at each extreme also shall be shown.

   (e) When deemed necessary, the Commission may require tests of frequency
   stability under conditions in addition to those specifically set out in
   paragraphs (a), (b), (c), and (d) of this section. (For example measurements
   showing the effect of proximity to large metal objects, or of various types
   of antennas, may be required for portable equipment.)

   [ 39 FR 5919 , Feb. 14, 1974, as amended at  51 FR 31304 , Sept. 2, 1986;  56 FR 11682 , Mar. 20, 1991. Redesignated at  63 FR 36599 , July 7, 1998.  68 FR 68545 , Dec. 9, 2003]