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The aircraft emergency frequency (also known in the USA as Guard) is a frequency used on the aircraft band reserved for emergency communications for aircraft in distress.The frequencies are 121.5 MHz for civilian, also known as International Air Distress (IAD), International Aeronautical Emergency Frequency, [1] or VHF Guard, [1] and 243.0 MHz—the second harmonic of VHF guard—for military ...
The US Coast Guard has said "beginning August 1st, 2013 the Coast Guard would no longer monitor 2182 kHz". [4] Many other MRCCs, for example most in Northern Europe, now only have MF capabilities and no HF. [5] Several HF maritime voice frequencies exist for long-distance distress calls: [6] 4125 kHz; 6215 kHz; 8291 kHz; 12290 kHz; 16420 kHz
A radio band is a small frequency band (a contiguous section of the range of the radio spectrum) in which channels are usually used or set aside for the same purpose. To prevent interference and allow for efficient use of the radio spectrum, similar services are allocated in bands.
A distress signal, also known as a distress call, is an internationally recognized means for obtaining help.Distress signals are communicated by transmitting radio signals, displaying a visually observable item or illumination, or making a sound audible from a distance.
Single Channel Ground and Airborne Radio System (SINCGARS) is a very high frequency combat network radio (CNR) used by U.S. and allied military forces. In the CNR network, the SINCGARS’ primary role is voice transmission between surface and airborne command and control (C2) assets.
It requires immediate delivery. Examples include reports of widespread civil disturbance, reports or warning of grave natural disaster, and requests for or directions concerning search and rescue operations. IMMEDIATE messages are processed, transmitted, and delivered in the order received and ahead of all messages of lower precedence.
For long-range communications with aircraft, Coast Guard stations use shortwave single-sideband communications. Weather and safety of navigation forecasts involve facsimile as well as other modes over shortwave and mediumwave transmissions. According to the NTIA, the Coast Guard is the seventh-biggest user of radio spectrum in the United States.
Coast Guard aircraft callsigns are almost always the word "Coast Guard" and the 4-digit aircraft number, e.g., "Coast Guard Six-Five-Seven-Niner," although other call signs may be used for special operations such as counter-narcotics interdiction. In tactical situations, the Marine Corps utilizes call signs naming conventions similar to the Army's.