Sec. 2.995  Measurements required: Frequency stability.

    (a) The frequency stability shall be measured with variation of 
ambient temperature as follows:
    (1) From -30 deg. to +50 deg. centigrade for all equipment except 
that specified in paragraphs (a) (2) and (3) of this section.
    (2) From -20 deg. to +50 deg. centrigrade 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, and equipment licensed for use 
aboard aircraft in the Aviation Services under part 87 of this chapter.
    (3) From 0 deg. to +50 deg. 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 deg. 
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

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shall be made after temperature stabilization at each of the ambient 
temperature levels; the lower temperature limit, 0 deg. centigrade and 
+30 deg. 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 deg. 
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]