Survival radios are carried by pilots and search and rescue teams to facilitate rescue in an emergency. They are generally designed to transmit on international distress frequencies. Maritime systems have been standardized under the

Global Maritime Distress Safety System The Global Maritime Distress and Safety System (GMDSS) is a worldwide system for automated emergency signal communication for ships at sea developed by the United Nations' International Maritime Organization (IMO) as part of the SOLAS Convention. ...

. Civil and military organisations utilized different frequencies to communicate and no infringement on either sector would take place. For emergencies involving civilian aircraft, the radio frequency used is VHF 121.5 MHz and for military aircraft incidents, the frequency used is UHF 243 MHz.

History

The use of radio to aid in rescuing survivors of accidents at sea came to the forefront after the sinking of the RMS ''Titanic'' in 1912. Lifeboats were equipped with

spark gap transmitter A spark-gap transmitter is an obsolete type of radio transmitter which generates radio waves by means of an electric spark."Radio Transmitters, Early" in Spark-gap transmitters were the first type of radio transmitter, and were the main type use ...

s such as the Marconi Type 241, c. 1920. These operated using

Morse code Morse code is a telecommunications method which Character encoding, encodes Written language, text characters as standardized sequences of two different signal durations, called ''dots'' and ''dashes'', or ''dits'' and ''dahs''. Morse code i ...

500 kHz From early in the 20th century, the radio frequency of 500 kilohertz (500 kHz) was an international calling and distress frequency for Morse code maritime communication. For much of its early history, this frequency was referred ...

, the international distress frequency at the time. This frequency had the advantage of long range due to ground-wave propagation and was constantly monitored by all large ships at sea after the'' Titanics sinking. However, due to its wavelength of 600 meters, a long antenna was required to achieve good range. Long wires on the order of 1/4 wavelength held up by kites or balloons were often used. Spark-gap continued to be used in lifeboats long after the technology was banned for general communication.

The Gibson Girl

During World War II, Germany developed a hand-crank 500 kHz rescue radio, the "Notsender" (emergency transmitter) NS2. It used two

vacuum tube A vacuum tube, electron tube, thermionic valve (British usage), or tube (North America) is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. It ...

s and was crystal-controlled. The radio case curved inward in the middle so that a user seated in an inflatable life boat could hold it stationary, between the thighs, while the generator handle was turned. The distress signal, in Morse code, was produced automatically as the crank handle was turned. An NS2 unit was captured by the British in 1941, who produced a copy, the Dinghy Transmitter Type T1333. Britain gave a second captured unit to the United States, which produced its own copy, the SCR-578.

United States Army Air Forces The United States Army Air Forces (USAAF or AAF) was the major land-based aerial warfare service component of the United States Army and ''de facto'' aerial warfare service branch of the United States during and immediately after World War II ...

aircraft carried the SCR-578 on over-water operations. Nicknamed the ''

Gibson Girl The Gibson Girl was the personification of the feminine ideal of physical attractiveness as portrayed by the pen-and-ink illustrations of artist Charles Dana Gibson during a 20-year period that spanned the late 19th and early 20th centuries ...

'' because of its hourglass shape, it was supplied with a fold-up metal frame

box kite A box kite is a high-performance Kite flying, kite, noted for developing relatively high Lift (force), lift; it is a type within the family of cellular kites. The typical design has four parallel struts. The box is made rigid with diagonal cros ...

, and a balloon with a small hydrogen generator, for which the flying line was the aerial wire. Power was provided by a hand cranked generator. The transmitter component was the BC-778. The frequency was

at 4.8 watts, giving it a range of . Keying could be automatic

SOS SOS is a Morse code distress signal (), used internationally, originally established for maritime use. In formal notation SOS is written with an overscore line (), to indicate that the Morse code equivalents for the individual letters of "SOS" a ...

(including the 4-second long dash for autoalarm), or manual.

Crystals A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macrosc ...

for frequency control were a scarce item for the U.S. during the war and the SCR-578 was not crystal-controlled. A post-World War II version, the AN/CRT-3, which added a frequency in the 8 MHz range, was in use by ships and civil aircraft until the mid-1970s.

VHF era

The use of aircraft for

search and rescue Search and rescue (SAR) is the search for and provision of aid to people who are in distress or imminent danger. The general field of search and rescue includes many specialty sub-fields, typically determined by the type of terrain the search ...

in World War II brought line-of-sight VHF radios into use. The much shorter wavelengths of VHF allowed a simple

dipole In physics, a dipole () is an electromagnetic phenomenon which occurs in two ways: * An electric dipole moment, electric dipole deals with the separation of the positive and negative electric charges found in any electromagnetic system. A simple ...

whip antenna A whip antenna is an antenna consisting of a straight flexible wire or rod. The bottom end of the whip is connected to the radio receiver or transmitter. A whip antenna is a form of monopole antenna. The antenna is designed to be flexible so ...

to be effective. Early devices included the British Walter, a compact single vacuum tube oscillator design operating at 177 MHz (1.7 meter wavelength), and the German Jäger (NS-4), a two-tube master oscillator power amplifier design at 58.5 and, later, 42 MHz. These were small enough to include in life rafts used on single-seat fighter aircraft. Post-war designs included the British Search And Rescue And Homing beacon (SARAH) beacon made by

Ultra Electronics Ultra Electronics Holdings is a British defence and security company. It was listed on the London Stock Exchange and was a constituent of the FTSE 250 Index until it was acquired by Cobham, which is itself owned by Advent International. The ...

, used in the location and recovery of astronaut

Scott Carpenter Malcolm Scott Carpenter (May 1, 1925 – October 10, 2013) was an American naval officer and aviator, test pilot, aeronautical engineer, astronaut, and aquanaut. He was one of the Mercury Seven astronauts selected for NASA's Project Mercury ...

after his Mercury space flight, the U.S. AN/URC-4 and the Soviet R 855U. These operated on the aircraft emergency frequencies of 121.5 and 243 MHz (2.5 and 1.2 meter wavelengths).

Automated beacon systems

After a light plane with two U.S. congressmen on board went down in 1972 and could not be found, the U.S. began requiring all aircraft to carry an

Emergency Locator Transmitter An emergency position-indicating radiobeacon (EPIRB) is a type of emergency locator beacon for commercial and recreational boats; it is a portable, battery-powered radio transmitter used in emergencies to locate boaters in distress and in nee ...

(ELT) that would turn on automatically in the event of a crash. Initially these units sent

beacon A beacon is an intentionally conspicuous device designed to attract attention to a specific location. A common example is the lighthouse, which draws attention to a fixed point that can be used to navigate around obstacles or into port. More mode ...

signals on the 121.5 MHz aircraft emergency frequency. These are being phased out in favor of ELTs that use a 406.025 MHz signal, which can be picked up by the

Cospas-Sarsat The International Cospas-Sarsat Programme is a satellite-aided search and rescue (SAR) initiative. It is organized as a treaty-based, nonprofit, intergovernmental, humanitarian cooperative of 45 nations and agencies (see infobox). It is dedica ...

international satellite system for search and rescue. Each 406 MHz beacon has a unique digital ID code. Users are required to register the code with the Cospas-Sarsat, allowing inquiries to be made when a distress signal is picked up. Some advanced models can transmit a location derived from an internal

GPS The Global Positioning System (GPS) is a satellite-based hyperbolic navigation system owned by the United States Space Force and operated by Mission Delta 31. It is one of the global navigation satellite systems (GNSS) that provide geol ...

GLONASS GLONASS (, ; ) is a Russian satellite navigation system operating as part of a radionavigation-satellite service. It provides an alternative to Global Positioning System (GPS) and is the second navigational system in operation with global cove ...

receiver. Maritime practice has shifted from rescue radios on 500 kHz distress frequency (which is no longer officially monitored) to the

, which includes use of the

system and other measures, including radar transponders and hand-held

marine VHF radio Marine VHF radio is a worldwide system of two way radio transceivers on ships and watercraft used for bidirectional voice communication from ship-to-ship, ship-to-shore (for example with harbormasters), and in certain circumstances ship-to-ai ...

s. There are many other types of

emergency locator beacon An emergency locator beacon is a radio beacon, a portable battery powered radio transmitter, used to geolocalization, locate airplanes, vessels, and persons in distress and in need of immediate rescue. Various types of emergency locator beacons ar ...

s that do not use the 406 MHz Cospas-Sarsat system, including man-overboard beacons that transmit

Automatic identification system The automatic identification system (AIS) is an automatic tracking system that uses transceivers on ships and is used by vessel traffic services (VTS). When satellites are used to receive AIS signatures, the term ''Satellite-AIS'' (S-AIS) is ...

beacons and

Avalanche transceiver An avalanche transceiver or avalanche beacon is a type of emergency locator beacon, a radio transceiver (a transmitter and receiver in one unit) operating at 457 kHz for the purpose of finding people buried under snow. They are widely carrie ...

U.S. Military survival radios

Military organizations still issue pilots and other combat personnel individual survival radios, which have become increasingly sophisticated, with built-in

Distance Measuring Equipment In aviation, distance measuring equipment (DME) is a radio navigation technology that measures the slant range (distance) between an aircraft and a ground station by timing the propagation delay of radio signals in the frequency band between 9 ...

(DME),

Global Positioning Satellite The Global Positioning System (GPS) is a satellite-based hyperbolic navigation system owned by the United States Space Force and operated by Mission Delta 31. It is one of the global navigation satellite systems (GNSS) that provide geol ...

(GPS) receivers, and satellite communication. In slang terms "PRC" radios were called a "''Prick''" followed by the model number, e.g. "Prick-25," and "URC" radios were called an "Erk." United States military survival radios include: *AN/CRC-7 - World War II era set, *AN/PRC-17 *AN/PRC-32 - Navy rescue sets, . *AN/PRC-49 *AN/PRC-63 - Smallest set built. *AN/PRC-90 - Vietnam War era airman rescue set. AN/PRC-90-1 and AN/PRC-90-2 are improved, repairable versions. Operates on 243 and 282.8 MHz AM. The PRC-90 also included a beacon mode, and a tone generator to allow the sending of Morse Code. *AN/PRC-103 - (Air Force) Rescue Swimmer Radio. *AN/PRC-112 - Offers Synthesized radio in the VHF and UHF aircraft bands. A PRC-112 and a hand held GPS were used by Capt.

Scott O'Grady Scott Francis O'Grady (born October 12, 1965) is a former United States Air Force (USAF) fighter pilot. On June 2, 1995, he was shot down over Bosnia and Herzegovina by a 2K12 Kub (NATO designation SA-6 "Gainful") mobile surface-to-air missile ...

when he was rescued after being shot down over

Bosnia Bosnia and Herzegovina, sometimes known as Bosnia-Herzegovina and informally as Bosnia, is a country in Southeast Europe. Situated on the Balkans, Balkan Peninsula, it borders Serbia to the east, Montenegro to the southeast, and Croatia to th ...

. The AN/PRC-112B, initially known as the Hook-112, is a PRC-112 modified to include a

receiver, allowing

encrypted In cryptography, encryption (more specifically, encoding) is the process of transforming information in a way that, ideally, only authorized parties can decode. This process converts the original representation of the information, known as plain ...

position information to be sent. Also has

beacon. The latest model AN/PRC-112G, built by

General Dynamics General Dynamics Corporation (GD) is an American publicly traded aerospace and defense corporation headquartered in Reston, Virginia. As of 2020, it was the fifth largest defense contractor in the world by arms sales and fifth largest in the Unit ...

can communicate with satellites as well. Over 31,000 radios in the PRC-112 family have been produced. *AN/PRC-125 (Navy) Rescue Swimmer Radio. *AN/PRC-149 Rescue Radio, replaced the PRC-90, PRC-112 and PRC-125 for non-combat use. Includes GPS and Cospas-Sarsat beacon. Operates on , , and . Built by

Tadiran Tadiran was an Israeli conglomerate founded in 1962 by the merger of two companies, Tadir and Ran. Tadiran had interests in electronics, home appliances (refrigeration and air conditioning), telecommunications, batteries, medical systems and defe ...

, the PRC-149 uses standard D cell batteries, unlike other units that took special batteries. *AN/PRQ-7 Combat Survivor/Evader Locator (CSEL) combines selective availability GPS, UHF line of sight and UHF satellite communications along with a

SARSAT The International Cospas-Sarsat Programme is a satellite-aided search and rescue (SAR) initiative. It is organized as a treaty-based, nonprofit, intergovernmental, humanitarian cooperative of 45 nations and agencies (see infobox). It is dedica ...

beacon. It can send predefined messages digitally along with the user's location. As of 2008, the PRQ-7 cost $7000 each. A rechargeable

lithium-ion A lithium-ion or Li-ion battery is a type of rechargeable battery that uses the reversible Intercalation (chemistry), intercalation of Li+ ions into electronically Electrical conductor, conducting solids to store energy. Li-ion batteries are c ...

battery pack cost $1600, while a non-rechargeable lithium-manganese dioxide unit cost $1520. As of Oct, 2011

Boeing The Boeing Company, or simply Boeing (), is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, and missiles worldwide. The company also provides leasing and product support s ...

has delivered 50,000 PRQ-7s. *AN/URC-4 - Operates at and *AN/URC-11 - Operating at , "A" versions replaced one audio tube with transistors. *AN/URC-10 - Subminiaturized, completely transistorized UHF radio sets consisting of a crystal-controlled receiver-transmitter, a 16-volt dry battery, and a power cable assembly. The unit operates on one channel in the band, usually at . *AN/URC-14 - Operates at *AN/URC-64 - (Air Force), 4 frequency rescue sets. Four crystal controlled channels between *AN/URC-68 - (Army), 4 frequency rescue sets.

References