As of 1997, most 360 channel radios (those with 50 kHz channel spacing) can no longer be used to transmit. A few 360 channel radios can be upgraded to meet the requirements (see below). The primary limitation is a technical specification that calls for a frequency tolerance standard of .003 percent, and almost all older 360 channel radios do not meet this standard. Newer 720 channel radios do meet this specification. Secondly, pilots need the ability to access applicable frequencies for a flight, and 360 channel radios do not allow the use of frequencies with 25 kHz channel spacing (for example .125 or .775). If a pilot needs to access one of these frequencies for his or her flight, they will need to have a 720 channel radio. ATC may be able to give an alternate frequency in some situations. This rule applies to all U.S. aircraft, including those that are no longer required to be licensed individually as radio stations.
Equipment Specifics Aircraft radios used to transmit must have been type accepted by the FCC as meeting a required frequency tolerance of .003 percent. Channel spacing and frequency tolerance specifications for a specific radio may be found by consulting the user's manual for the unit, by contacting the manufacturer, or by consulting a local aircraft radio dealer or repair shop.
A radio which has not been type accepted as .003 percent may only be brought into compliance through the installation of an FCC type accepted "upgrade kit," which may be available from the unit's manufacturer. The upgrade kit will have an FCC ID number. Very few manufacturers offer FCC type accepted upgrade kits. If a kit is not available for a particular model of radio, the radio may not be adjusted and may not be used to transmit. If no kit is available, the radio may be allowed to remain in the aircraft provided the intent is not to use it to transmit radio signals (e.g., receive-only operation, an integral part of a navigation/communications unit, or decoration in a vintage aircraft). The radio should be placarded "do not use to transmit" or removed from the aircraft.
List of avionics manufacturers
*The Cessna RT308C, 328C, and Genava 600 may meet the applicable standards. The King KX 170 and 175 may be able to be upgraded. Check with the avionics manufacturers for further details.
The FCC first authorized the use of 25 kHz VHF aircraft radios in 1972, over the strong protests of AOPA and other aviation groups. Because of AOPA's advocacy efforts, it wasn't until over 19 years later that the FCC eliminated the use of most 50 kHz channeled VHF aircraft radios to transmit. The FCC contended that the 50 kHz radios were usually "found in private, single engine aircraft operating in rural areas." Although AOPA continued to strongly oppose the action because of the economic impact on general aviation pilots, it passed with the support of the FAA; Aeronautical Radio, Inc.; the Air Line Pilots Association; the Air Transport Association; and the National Business Aircraft Association, Inc. All of these groups noted that users of the older radios would have limited access to FAA air traffic control channels, would experience flight delays in FAA controlled airspace, and would be unable to utilize newly available aviation frequencies in the 136-137 MHz band. /p>
The Commission adopted the .003 percent frequency tolerance in 1984 in order to conform its rules with those adopted internationally in the Final Acts of the World Administrative Radio Conference, Geneva, 1979. At that time, this action was also endorsed by the Federal Aviation Administration (FAA) and was also strongly supported by Aeronautical Radio, Inc., the Air Line Pilots Association, the Air Transport Association, and the National Business Aircraft Association, Inc. This action was found to be consistent with the FAA's three-phase plan to implement 25 kHz channel spacing in the 118-137 MHz band, which creates more radio channels for use by pilots.
For additional assistance, please contact:
AOPA Pilot Information Center
Updated Tuesday, June 3, 2008, 4:01 PM