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),  Tolerance \1\      Tolerance \2\   
     and categories of stations                                         
------------------------------------------------------------------------
(1) Band-9 to 535 kHz:                                                  
  Aeronautical stations............          100    100                 
  Aircraft stations................          200    100                 
  Survival craft stations on 500           5,000    20 Hz \3\           
   kHz.                                                                 

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  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            200    20 Hz \3\           
   kHz.                                                                 
(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            200    50 Hz \3\           
   kHz.                                                                 
(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                50    30                  
     less).                                                             
    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-100 to 137 MHz:                                                
  Aeronautical stations............       \4\ 50    20                  
  Emergency locator transmitter               50    50                  
   test stations.                                                       
  Survival craft stations on 121.5            50    50                  
   MHz.                                                                 
  Emergency locator stations.......           50    50                  
  Aircraft and other mobile               50 \5\    30 \10\             
   stations in the Aviation                                             
   Services.                                                            
  Radionavigation stations.........           20    20                  
(6) Band-137 to 470MHz:                                                 
  Aeronautical stations............           50    20                  
  Survival craft stations on 243              50    50                  
   MHz.                                                                 
  Aircraft stations................       50 \5\    30 \10\             
  Radionavigation stations.........           50    50                  
  Emergency locator transmitters on          N/A    5                   
   406 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  1250 \6\, \9\       
(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 type accepted or type approved after November
  30, 1977.                                                             
\4\ The tolerance for transmitters type accepted between January 1,     
  1966, and January 1, 1974, is 30 parts in 10 \6\. The tolerance for   
  transmitters type accepted after January 1, 1974, and stations using  
  offset carrier techniques is 20 parts in 10 \6\.                      
\5\ The tolerance for transmitters type accepted 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 type acceptance, a tolerance of 160 Hz applies to  
  the reference oscillator of the AES transmitter. This is a bench test.

    (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 other than Civil Air Patrol.....10 
                                                                      Hz
(2) All aircraft stations other than Civil Air Patrol..............20 Hz
(3) Civil Air Patrol Stations......................................50 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.

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    (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]