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Federal Search and Rescue Communications on 243 MHz (NTIA)
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The footnotes 5.111, 5.199, and 5.256 were adopted by the International Telecommunication Union and are incorporated into the U.S. Table of Frequency Allocations. Among other things, these footnotes provide for the use of the 243 MHz frequency for search and rescue purposes.
The frequency 243 MHz is used on the radios onboard most Federal aircraft as a special channel, called a "guard" channel that is used for distress and safety purposes, including search and rescue. The 243 MHz channel is always activated on aircraft and ground systems even though another channel may be in use on a transceiver operating in the band. For example, a military aircraft in distress could make an emergency distress call for assistance on 243 MHz, and all other aircraft or ground stations in the area would hear it immediately and take action.
In general, the band 225-328.6 MHz is reserved for military uses by North Atlantic Treaty Organization (NATO), its member nations, and other U.S. allies. The band is harmonized among NATO-member nations for secure communications.
(Information extracted from the NTIA Federal Government Spectrum Use Reports, dated December 1, 2015)
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Frequencies |
| Frequency | Bandwidth | Use | Service | Table |
| 243 MHz | 25 kHz | Federal Search and Rescue | Mobile | F |
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