(a) Unless noted elsewhere, transmitters used in the services governed by this part must have a minimum frequency stability as specified in the following table.
Minimum Frequency Stability
[Parts per million (ppm)]------------------------------------------------------------------------
Mobile stations
-----------------
Fixed and Over 2 2 watts
Frequency range (MHz) base watts or less
stations output output
power power------------------------------------------------------------------------Below 25................................. \1 2 3\ 100 100 20025-50 20 20 5072-76.................................... 5 ....... 50150-174.................................. \5 11\ 5 \6\ 5 \4 6\
50216-220.................................. 1.0 ....... 1.0220-222 \12\............................. 0.1 1.5 1.5421-512.................................. \7 11 14\ \8\ 5 \8\ 5
2.5806-809.................................. \14\ 1.0 1.5 1.5809-824.................................. \14\ 1.5 2.5 2.5851-854.................................. 1.0 1.5 1.5854-869.................................. 1.5 2.5 2.5896-901.................................. \14\ 0.1 1.5 1.5902-928.................................. 2.5 2.5 2.5902-928 \13\............................. 2.5 2.5 2.5929-930.................................. 1.5 ....... .......935-940.................................. 0.1 1.5 1.51427-1435................................ \9\ 300 300 300Above 2450 \10\.......................... ........... ....... .......------------------------------------------------------------------------\1\ Fixed and base stations with over 200 watts transmitter power must
have a frequency stability of 50 ppm except for equipment used in the
Public Safety Pool where the frequency stability is 100 ppm.\2\ For single sideband operations below 25 MHz, the carrier frequency
must be maintained within 50 Hz of the authorized carrier frequency.\3\ Travelers information station transmitters operating from 530-1700
kHz and transmitters exceeding 200 watts peak envelope power used for
disaster communications and long distance circuit operations pursuant
to Sec. Sec. 90.242 and 90.264 must maintain the carrier frequency
to within 20 Hz of the authorized frequency.\4\ Stations operating in the 154.45 to 154.49 MHz or the 173.2 to 173.4
MHz bands must have a frequency stability of 5 ppm.
\5\ In the 150-174 MHz band, fixed and base stations with a 12.5 kHz
channel bandwidth must have a frequency stability of 2.5 ppm. Fixed
and base stations with a 6.25 kHz channel bandwidth must have a
frequency stability of 1.0 ppm.\6\ In the 150-174 MHz band, mobile stations designed to operate with a
12.5 kHz channel bandwidth or designed to operate on a frequency
specifically designated for itinerant use or designed for low-power
operation of two watts or less, must have a frequency stability of 5.0
ppm. Mobile stations designed to operate with a 6.25 kHz channel
bandwidth must have a frequency stability of 2.0 ppm.\7\ In the 421-512 MHz band, fixed and base stations with a 12.5 kHz
channel bandwidth must have a frequency stability of 1.5 ppm. Fixed
and base stations with a 6.25 kHz channel bandwidth must have a
frequency stability of 0.5 ppm.\8\ In the 421-512 MHz band, mobile stations designed to operate with a
12.5 kHz channel bandwidth must have a frequency stability of 2.5 ppm.
Mobile stations designed to operate with a 6.25 kHz channel bandwidth
must have a frequency stability of 1.0 ppm.\9\ Fixed stations with output powers above 120 watts and necessary
bandwidth less than 3 kHz must operate with a frequency stability of
100 ppm. Fixed stations with output powers less than 120 watts and
using time-division multiplex, must operate with a frequency stability
of 500 ppm.\10\ Except for DSRCS equipment in the 5850-5925 MHz band, frequency
stability is to be specified in the station authorization. Frequency
stability for DSRCS equipment in the 5850-5925 MHz band is specified
in subpart M of this part.\11\ Paging transmitters operating on paging-only frequencies must
operate with frequency stability of 5 ppm in the 150-174 MHz band and
2.5 ppm in the 421-512 MHz band.\12\ Mobile units may utilize synchronizing signals from associated base
stations to achieve the specified carrier stability.\13\ Fixed non-multilateration transmitters with an authorized bandwidth
that is more than 40 kHz from the band edge, intermittently operated
hand-held readers, and mobile transponders are not subject to
frequency tolerance restrictions.\14\ Control stations may operate with the frequency tolerance specified
for associated mobile frequencies.
(b) For the purpose of determining the frequency stability limits, the power of a transmitter is considered to be the maximum rated output power as specified by the manufacturer.[60 FR 37266, July 19, 1995, as amended at 61 FR 4235, Feb. 5, 1996; 61 FR 18986, Apr. 30, 1996; 61 FR 38403, July 24, 1996; 62 FR 2040, Jan. 15, 1997; 62 FR 18927, Apr. 17, 1997; 67 FR 41860, June 20, 2002; 69 FR 46443, Aug. 3, 2004; 69 FR 67838, Nov. 22, 2004]