Sec.  87.133   Frequency stability.

   (a) Except as provided in paragraphs (c), (d), and (f) of this section, the
   carrier frequency of each station must be maintained within these
   tolerances:


------------------------------------------------------------------------
 Frequency band (lower limit exclusive,
 upper limit inclusive), and categories  Tolerance      Tolerance \2\
              of stations                   \1\
------------------------------------------------------------------------
(1) Band-9 to 535 kHz:
  Aeronautical stations................        100  100
  Aircraft stations....................        200  100
  Survival craft stations on 500 kHz...      5,000  20 Hz \3\
  Radionavigation stations.............        100  100
(2) Band-1605 to 4000 kHz:
  Aeronautical fixed stations:
    Power 200 W or less................        100  100 \8\
    Power above 200 W..................         50  50 \8\
  Aeronautical stations:
    Power 200 W or less................    100 \7\  100 7, 8
    Power above 200 W..................     50 \7\  50 7, 8
  Aircraft stations....................    100 \7\  100 \7\
  Survival craft stations on 2182 kHz..        200  20 Hz \3\
(3) Band-4 to 29.7 MHz:
  Aeronautical fixed stations:
    Power 500 W or less................         50  ....................
    Power above 500 W..................         15  ....................
  Single-sideband and Independent-
   sideband emission:
    Power 500 W or less................             50 Hz
    Power above 500 W..................             20 Hz
  Class F1B emissions..................             10 Hz
  Other classes of emission:
    Power 500 W or less................             20
    Power above 500 W..................             10
  Aeronautical stations:
    Power 500 W or less................    \7\ 100  100 \7\
    Power above 500 W..................     \7\ 50  50 \7\
  Aircraft stations....................    \7\ 100  100 \7\
  Survival craft stations on 8364 kHz..        200  50 Hz \3\
(4) Band-29.7 to 100 MHz:
  Aeronautical fixed stations:
    Power 200 W or less................         50  ....................
    Power above 200 W..................         30  ....................
    Power 50 W or less.................             30
    Power above 50 W...................             20
  Operational fixed stations:
    73-74.6 MHz (Power 50 W or less)...         50  30
    73-74.6 MHz (Power above 50 W).....         20  20
    72-73.0 MHz and 75.4-76.0 MHz......          5  5
  Radionavigation stations.............        100  50
(5) Band-108 to 137 MHz:
    Aeronautical stations..............     \4\ 50  \12\ 20
  Emergency locator transmitter test            50  50
   stations.
  Survival craft stations on 121.5 MHz.         50  50
  Emergency locator stations...........         50  50
    Aircraft and other mobile stations      \5\ 50  \13\ 30
     in the Aviation Services.
  Radionavigation stations.............         20  20
  Differential GPS.....................  .........  2
(6) Band-137 to 470MHz:
  Aeronautical stations................         50  20
  Survival craft stations on 243 MHz...         50  50
  Aircraft stations....................     50 \5\  30 \10\
  Radionavigation stations.............         50  50
  Emergency locator transmitters on 406        N/A  5
   MHz.
(7) Band-470 to 2450 MHz:
  Aeronautical stations................        100  20
  Aircraft stations....................        100  20
  Aircraft earth station...............  .........  320 Hz \11\
  Radionavigation stations:
    470-960 MHz........................        500  500
    960-1215 MHz.......................         20  20
    1215-2450 MHz......................        500  500
(8) Band-2450 to 10500 MHz:
  Radionavigation stations.............   \6\, \9\  1250 \6\, \9\
                                              1250
(9) Band-10.5 GHz to 40 GHz:
  Radionavigation stations.............       5000  5000
------------------------------------------------------------------------
\1\ This tolerance is the maximum permitted until January 1, 1990, for
  transmitters installed before January 2, 1985, and used at the same
  installation. Tolerance is indicated in parts in 10 \6\ unless shown
  as Hertz (Hz).
\2\ This tolerance is the maximum permitted after January 1, 1985 for
  new and replacement transmitters and to all transmitters after January
  1, 1990. Tolerance is indicated in parts in 10 \6\ unless shown as
  Hertz (Hz).
\3\ For transmitters first approved after November 30, 1977.
\4\ The tolerance for transmitters approved between January 1, 1966, and
  January 1, 1974, is 30 parts in 10 \6\. The tolerance for transmitters
  approved after January 1, 1974, and stations using offset carrier
  techniques is 20 parts in 10 \6\.
\5\ The tolerance for transmitters approved after January 1, 1974, is 30
  parts in 10 \6\.
\6\ In the 5000 to 5250 MHz band, the FAA requires a tolerance of
   ±10 kHz for Microwave Landing System stations which are to be a
  part of the National Airspace System (FAR 171).
\7\ For single-sideband transmitters operating in the frequency bands
  1605-4000 kHz and 4-29.7 MHz which are allocated exclusively to the
  Aeronautical Mobile (R) Service, the tolerance is: Aeronautical
  stations, 10 Hz; aircraft stations, 20 Hz.
\8\ For single-sideband radiotelephone transmitters the tolerance is: In
  the bands 1605-4000 kHz and 4-29.7 MHz for peak envelope powers of 200
  W or less and 500 W or less, respectively, 50 Hz; in the bands 1605-
  4000 kHz and 4-29.7 MHz for peak envelope powers above 200 W and 500
  W, respectively, 20 Hz.
\9\ Where specific frequencies are not assigned to radar stations, the
  bandwidth occupied by the emissions of such stations must be
  maintained within the band allocated to the service and the indicated
  tolerance does not apply.
\10\ Until January 1, 1997, the maximum frequency tolerance for
  transmitters with 50 kHz channel spacing installed before January 2,
  1985, is 50 parts in 10 \6\.
\11\ For purposes of certification, a tolerance of 160 Hz applies to the
  reference oscillator of the AES transmitter. This is a bench test.
\12\ For emissions G1D and G7D, the tolerance is 2 parts per 106.
\13\ For emissions G1D and G7D, the tolerance is 5 parts per 106.

   (b) The power shown in paragraph (a) of this section is the peak envelope
   power for single-sideband transmitters and the mean power for all other
   transmitters.

   (c) For single-sideband transmitters, the tolerance is:

   (1) All aeronautical stations on land—10 Hz.

   (2) All aircraft stations—20 Hz.

   (d) For radar transmitters, except non-pulse signal radio altimeters, the
   frequency at which maximum emission occurs must be within the authorized
   frequency band and must not be closer than 1.5/T MHz to the upper and lower
   limits of the authorized bandwidth, where T is the pulse duration in
   microseconds.

   (e) The Commission may authorize tolerances other than those specified in
   this section upon a satisfactory showing of need.

   (f) The carrier frequency tolerance of transmitters operating in the
   1435–1535 MHz and 2310–2390 MHz bands manufactured before January 2, 1985,
   is 0.003 percent. The carrier frequency tolerance of transmitters operating
   in the 1435–1535 MHz and 2310–2390 MHz bands manufactured after January 1,
   1985, is 0.002 percent. After January 1, 1990, the carrier frequency
   tolerance of all transmitters operating in the 1435–1535 MHz and 2310–2390
   MHz bands is 0.002 percent.

   [ 53 FR 28940 , Aug. 1, 1988, as amended at  56 FR 38084 , Aug. 12, 1991;  57 FR 45749 , Oct. 5, 1992;  58 FR 31027 , May 26, 1993;  63 FR 36607 , July 7, 1998;
    64 FR 27474 , May 20, 1999;  66 FR 26799 , May 15, 2001;  69 FR 32880 , June 14,
   2004]