Radios operating in the very high frequency maritime mobile band
A standard handheld marine VHF, mandatory on larger seagoing vessels under the GMDSS rulesA VHF set and a VHF channel 70 DSC set, the DSC on topA vintage (76-89) marine VHF radiotelephone
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-aircraft. It uses FM channels in the very high frequency (VHF) radio band in the frequency range between 156 and 174MHz, designated by the International Telecommunication Union as the VHF maritime mobile band. In some countries additional channels are used, such as[1] the L and F channels for leisure and fishing vessels in the Nordic countries (at 155.5–155.825MHz). Transmitter power is limited to 25 watts, giving them a range of about 100 kilometres (62mi; 54nmi).
Marine VHF radio equipment is installed on all large ships and most seagoing small craft. It is also used, with slightly different regulation, on rivers and lakes. It is used for a wide variety of purposes, including marine navigation and traffic control, summoning rescue services and communicating with harbours, locks, bridges and marinas.
Background
Marine radio was the first commercial application of radio technology, allowing ships to keep in touch with shore and other ships, and send out a distress call for rescue in case of emergency. Guglielmo Marconi invented radio communication in the 1890s, and the Marconi Company installed wireless telegraphy stations on ships beginning around 1900. Marconi built a string of shore stations and in 1904 established the first Morse code distress call, the letters CQD, used until 1906 when SOS was agreed on. The first significant marine rescue due to radio was the 1909 sinking of the luxury liner RMS Republic, in which 1,500 lives were saved. This and the 1912 RMS Titanic rescue brought the field of marine radio to public consciousness, and marine radio operators were regarded as heroes. By 1920, the US had a string of 12 coastal stations stretched along the Atlantic seaboard from Bar Harbor, Maine to Cape May, New Jersey.[2]
The first marine radio transmitters used the longwave bands. During World WarI amplitude modulation was developed, and in the 1920s spark radiotelegraphy equipment was replaced by vacuum tuberadiotelephony allowing voice communication. Also in the 1920s, the ionospheric skip or skywave phenomenon was discovered, which allowed lower power vacuum tube transmitters operating in the shortwave bands to communicate at long distances.
Hoping to foil German detection during the World War II Battle of the Atlantic, American and British convoy escorts used Talk-Between-Ships (TBS) radios operating on VHF.[3]
Types of equipment
Sets can be fixed or portable. A fixed set generally has the advantages of a more reliable power source, higher transmit power, a larger and more effective antenna and a bigger display and buttons. A portable set (often essentially a waterproof, VHF walkie-talkie in design) can be carried on a kayak, or to a lifeboat in an emergency, has its own power source and is waterproof if GMDSS-approved. A few portable VHFs are even approved to be used as emergency radios in environments requiring intrinsically safe equipment (e.g. gas tankers, oil rigs, etc.).
Voice-only
Voice only equipment is the traditional type, which relies totally on the human voice for calling and communicating. Many lower priced handheld units are voice only as well as older fixed units.
DSC equipment, a part of the Global Maritime Distress Safety System (GMDSS), provides all the functionality of voice-only equipment and, additionally, allows several other features:
The ability to call another vessel using a unique identifier known as a Maritime Mobile Service Identity (MMSI). This information is carried digitally and the receiving set will alert the operator of an incoming call once its own MMSI is detected. Calls are set up on the dedicated VHF channel 70 which DSC equipment must listen on continuously. The actual voice communication then takes place on a different channel specified by the caller.
A distress button, which automatically sends a digital distress signal identifying the calling vessel and the nature of the emergency
A built in GPS receiver or facility to connect an external GPS receiver so that the user's location may be transmitted automatically along with a distress call.
When a DSC radio is bought new the user will get the opportunity to program it with the MMSI number of the ship it is intended to be used on. However to change the MMSI after the initial programming can be problematic and require special proprietary tools. This is allegedly done to prevent theft.
More advanced transceiver units support AIS. This relies on a GPS receiver built into the VHF equipment or an externally connected one by which the transceiver obtains its position and transmits this information along with some other details about the ship (MMSI, cargo, draught, destination and some others) to nearby ships. AIS operates as a mesh network and full featured units relay AIS messages from other ships, greatly extending the range of this system; however some low-end units are receive only or do not support the relaying functionality.
Using the RTCM 12301.1 standard it is possible to send and receive text messages in a similar fashion to SMS between marine VHF transceivers which comply with this standard.[5] However, as of 2019 very few transceivers support this feature. The recipient of the message needs to be tuned to the same channel as the transmitting station in order to receive it.
Regulation
In the United States, any person can legally purchase a Marine VHF radio and use it to communicate without requiring any special license as long as they abide by certain rules, but in a great many other countries a license is required to transmit on Marine VHF frequencies.
In the United Kingdom and Ireland and some other European countries Short Range Certificate is the minimum requirement to use an installed marine VHF radio. This is usually obtained after completing a course of around two days and passing an exam. This is intended for those operating on lakes and in coastal areas whereas a Long Range Certificate is usually recommended for those operating further out as it also covers HF and MF radios as well as INMARSAT systems. A basic marine portable radio license is available without testing.[6]
Automatic Transmitter Identification System (marine)
For use on the inland waterways within continental Europe, a compulsory Automatic Transmitter Identification System (ATIS) transmission conveys the vessel's identity after each voice transmission. This is a ten-digit code that is either an encoded version of the ship's alphanumeric call sign, or for vessels from outside the region, the ship MMSI prefixed with "9". The requirement to use ATIS in Europe, and which VHF channels may be used, are strongly regulated, most recently by the Basel agreements.
Channels and frequencies
A marine VHF set is a combined transmitter and receiver and only operates on standard, international frequencies known as channels. Channel 16 (156.8MHz) is the international calling and distress channel. Transmission power ranges between 1 and 25 watts, giving a maximum range of up to about 60 nautical miles (111km) between aerials mounted on tall ships and hills, and 5 nautical miles (9km; 6mi) between aerials mounted on small boats at sea level.[7]Frequency modulation (FM) is used, with vertical polarization, meaning that antennas have to be vertical in order to have good reception. For longer range communication at sea, marine MF and marine HF bands and satellite phones can be used.
Half-duplex channels here are listed with the A and B frequencies the same. The frequencies, channels, and some of their purposes are governed by the ITU. For an authoritative list see.[8] The original allocation of channels consisted of only channels 1 to 28 with 50kHz spacing between channels, and the second frequency for full-duplex operation 4.6MHz higher.
Improvements in radio technology later meant that the channel spacing could be reduced to 25kHz with channels 60 to 88 interspersed between the original channels.
Channels 75 and 76 are omitted as they are either side of the calling and distress channel 16, acting as guard channels. The frequencies which would have been the second frequencies on half-duplex channels are not used for marine purposes and can be used for other purposes that vary by country. For example, 161.000 to 161.450MHz are part of the allocation to the Association of American Railroads channels used by railways in the US and Canada.[9][10]
Ship-to-ship/shore, commercial and safety West Coast A
Public correspondence (ship-to-shore full-duplex) BC Coast
Public correspondence (ship-to-shore full-duplex) port operations
Public correspondence (ship-to-shore full-duplex), Independent radio networks
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways.. (ship-to-shore full-duplex)
2
156.100
160.700
Public BC Coast
Public correspondence (ship-to-shore full-duplex) port operations
Public correspondence (ship-to-shore full-duplex), Independent radio networks
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways.. (ship-to-shore full-duplex)
Public correspondence (ship-to-shore full-duplex) port operations
Public correspondence (ship-to-shore full-duplex), Independent radio networks, CustomsCoast Guard, search and rescue
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways. (ship-to-shore full-duplex)
4
156.200
160.800
Ship-to-ship/shore, commercial and safety East Coast and Inland A
Canadian Coast Guard - public working channel BC Coast[lower-alpha 2]A
Boat to boat Tutukaka/Raglan
Public correspondence (ship-to-shore full-duplex) port operations
Public correspondence (ship-to-shore full-duplex), independent radio networks, customs, coast guard, search and rescue
Public correspondence (ship-to-shore full-duplex), independent radio networks
5
156.250
160.850
Ship movements
Public correspondence (ship-to-shore full-duplex) port operations
Public correspondence (ship-to-shore full-duplex), independent radio networks, authorities responsible
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore full-duplex)
6
156.300
156.300
Ship-to-ship and ship-to-air A
Ship-to-ship and ship-to-air A
Distress ship-to-air
Inter-ship working
A Ship-to-ship (commercial) also SAR: Ship-to-ship and ship-to-air
A Ship-to-ship and ship-to-air
Ship-to-ship (limited to 1 watt) and ship-to-air
7
156.350
160.950
General working channel
Public correspondence (ship-to-shore full-duplex) port operations
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore full-duplex)
8
156.400
156.400
Ship-to-ship A
Ship-to-ship East and west coasts, Lake Winnipeg A
Inter-ship working
Inter-ship working
A Ship-to-ship (commercial)
A Ship-to-ship
A Ship-to-ship (limited to 1 watt)
9
156.450
156.450
Frequently used by pilots A
Calling A, commercial and non-commercial.
Ship-to-air for maritime support Atlantic and BC coasts A
Pilots, port operations
Port operations
A VTS Ship-to-ship + port operations
Marina pilots, marina operations, ship in a marina
Marina pilots, marina operations, ship in a marina, limited to 1 watt
10
156.500
156.500
Frequently used by HM Coastguard A
Ship-to-air - SAR and antipollution A General working - Atlantic and BC coasts, Great Lakes
Port operations
A Ship-to-ship port operations also SAR and oil cleanup only VTS on Gulf of Finland
Radiocommunications on board a ship or in a group of boats towed or pushed, as well as those concerning the instructions for the maneuver bullish and docking, limited to 1 watt
Radiocommunications on board a ship or in a group of boats towed or pushed, as well as those concerning the instructions for the maneuver bullish and docking. (limited to 1 watt)
18
156.900
161.500
Public correspondence (ship-to-shore full-duplex) port operations
Public correspondence (ship-to-shore full-duplex), Independent radio networks
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore full-duplex)
19
156.950
161.550
Landside facilities: harbormaster, marinas.
Canadian Coast Guard working channel
Public correspondence (ship-to-shore full-duplex) port operations
Public correspondence (ship-to-shore full-duplex), port operations
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore full-duplex)
20
157.000
161.600
Repeater operations
Continuous weather Maritime Safety Service
Public correspondence (ship-to-shore full-duplex) port operations
Port operations, Public correspondence (ship-to-shore full-duplex)
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore full-duplex), (limited to 1 watt Paris Underground canal)
Public correspondence (ship-to-shore full-duplex) port operations
Port operations, public correspondence (ship-to-shore full-duplex)
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore full-duplex)
23
157.150
161.750
HM Coastguard Maritime Safety Information: now on 62, 63, 64.
A U.S. Coast Guard Only
Continuous weather Maritime Safety Service
Public correspondence (ship-to-shore full-duplex) port operations
Port operations, Public correspondence (ship-to-shore full-duplex)
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore full-duplex), Independent radio networks
Public correspondence (ship-to-shore full-duplex) port operations
Public correspondence (ship-to-shore full-duplex), Independent radio networks
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore full-duplex)
25
157.250
161.850
Maritime radio working channel
Public correspondence (ship-to-shore full-duplex) port operations
Public correspondence (ship-to-shore full-duplex), Independent radio networks
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore full-duplex)
26
157.300
161.900
HM Coastguard Maritime Safety Information
Public correspondence (marine telephone operator)
Public correspondence (ship-to-shore full-duplex) port operations
Public correspondence (ship-to-shore full-duplex), Independent radio networks
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore full-duplex)
27
157.350
161.950
Public correspondence (ship-to-shore full-duplex) port operations
Public correspondence (ship-to-shore full-duplex), independent radio networks
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore full-duplex)
28
157.400
162.000
Public correspondence (ship-to-shore full-duplex) port operations
Public correspondence (ship-to-shore full-duplex), independent radio networks
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore full-duplex)
31
157.550
162.150
(The Netherlands) Marina channel public correspondence (ship-to-shore full-duplex)
M1/37A
157.850
157.850
(As M1) Yacht clubs, race committees and marinas
60
156.025
160.625
GOFREP on Gulf of Finland public correspondence (ship-to-shore full-duplex) port operations
Public correspondence (ship-to-shore full-duplex), Independent radio networks
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore full-duplex)
GOFREP (Estonia) on Gulf of Finland Public correspondence (ship-to-shore full-duplex) port operations
Public correspondence (ship-to-shore full-duplex), Independent radio networks
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore full-duplex)
Public correspondence (ship-to-shore full-duplex) port operations
Public correspondence (ship-to-shore full-duplex), independent radio networks
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore full-duplex)
63
156.175
160.775
HM Coastguard Maritime Safety Information (half-duplex)[lower-alpha 4]
Boat to boat - Manukau
Public correspondence (ship-to-shore full-duplex) port operations
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore full-duplex)
64
156.225
160.825
HM Coastguard Maritime Safety Information (half-duplex)[lower-alpha 4]
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore full-duplex)
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore duplex)
66
156.325
160.925
A BC coast marinas
Public correspondence (ship-to-shore duplex) port operations
Public correspondence (ship-to-shore duplex), Independent radio networks
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore duplex)
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore duplex)
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore duplex)
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore duplex)
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore duplex)
74
156.725
156.725
British Waterways/Canal and River Trust Channel (Canal and River System)
Navigation related communications, limited to 1 watt
ARestricted ship-to-ship port operations
ARestricted ship-to-ship port operations, (limited to 1 watt)
Port operations
76
156.825
156.825
A Restricted port operations
ARestricted ship-to-ship port operations, (limited to 1 watt)
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore duplex)
77
156.875
156.875
Ship-to-ship A
Ship-to-ship
A Ship-to-ship
A Ship-to-ship, communications with a social (ship)
A Ship-to-ship, communications with a social (ship), limited to 1 watt
78
156.925
161.525
Non-commercial A
Public correspondence (ship-to-shore duplex) port operations
Public correspondence (ship-to-shore duplex), independent radio networks
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore duplex)
79
156.975
161.575
Public correspondence (ship-to-shore duplex) port operations
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore duplex)
80
157.025
161.625
UK marina channel
Repeater operations
Coastguard radio working channel
GOFREP on Gulf of Finland public correspondence (ship-to-shore duplex) port operations
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore duplex)
81
157.075
161.675
A U.S. Government Use Only
Repeater Operations
Coastguard radio working channel
GOFREP (Estonia) on Gulf of Finland public correspondence (ship-to-shore duplex) port operations
Public correspondence (ship-to-shore duplex), independent radio networks
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore duplex)
82
157.125
161.725
A U.S. Government use only
Canadian Coast Guard working channel
Coastguard radio working channel
Public correspondence (ship-to-shore duplex) port operations
Port operations
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore duplex)
83
157.175
161.775
A U.S. Coast Guard use only
Canadian Coast Guard working channel
Public correspondence (ship-to-shore duplex) port operations
Public correspondence (ship-to-shore duplex) port operations
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore duplex)
84
157.225
161.825
HM Coastguard Maritime Safety Information: now on 62, 63, 64.
Coastguard radio working channel
Public correspondence (ship-to-shore duplex) port operations
Public correspondence (ship-to-shore duplex), Independent radio networks
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore duplex)
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore duplex)
86
157.325
161.925
HM Coastguard Maritime Safety Information: now on 62, 63, 64.
Coastguard radio working channel
Public correspondence (ship-to-shore duplex) port operations
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore duplex)
87
157.375
157.375
Public correspondence port operations
Public correspondence (ship-to-shore duplex), independent radio networks, customs, Coast Guard, search and rescue
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore duplex)
88
157.425
157.425
Commercial, inter-ship only
Public correspondence (ship-to-shore duplex), independent radio networks
Radiotelephone links between ship stations and land stations of the authorities responsible for the operation of inland waterways (ship-to-shore duplex)
M2/P4
161.425
161.425
(As M2) Yacht clubs, race committees and marinas
(As P4) In France, some yacht clubs, marinas and race committees
(Ship-to-ship) Used in the Nordic countries and Estonia
L2
155.525
155.525
Leisure activities
(Ship-to-ship) Used in the Nordic countries and Estonia
L3
155.650
155.650
Leisure activities
(Ship-to-ship) Used in Finland and Norway
F1
155.625
155.625
Fishing
(Ship-to-ship) Used in the Nordic countries
F2
155.775
155.775
Fishing
(Ship-to-ship) Used in the Nordic countries
F3
155.825
155.825
Fishing, also recreational fishing
(Ship-to-ship) Used in the Nordic countries
1 2 3 Some radios enable channels 3A, 61A, and 64A when configured for "USA mode" even though those channels are allocated exclusively for Public Safety use by the FCC. The frequencies 156.075, 156.150, and 156.225MHz are used for interoperability communication by police and fire departments in many areas.
↑ CCG public operations moved from 22A to 04A to avoid interference from USCG stations in northern Washington state.
↑ Channel 22A is reserved for communication between the U.S. Coast Guard vessels and private vessels. The Coast Guard does not monitor 22A: Contact must first be established on 16.
1 2 3 4 5 UKSAR land-based search and rescue teams have access to the half-duplexed versions of 24, 62, 63, 64, 85 for operational and training needs. These include mountain rescue teams in England, Wales and Scotland.
Operating procedure
Marine VHF mostly uses half-duplex non-relayed transmission. Ship to ship communication is over a single radio frequency, while ship to shore uses two frequencies, but typically only one of the parties can transmit at a time. (Not to be confused with simplex communication, for example radio broadcasting, where one party transmits always transmits.) The transceiver is normally in receive mode; to transmit the user presses a "push to talk" button on the set or microphone which turns the transmitter on and the receiver off. Some channels, however, are "duplex" transmission channels where communication can take place in both directions simultaneously when the equipment on both ends allow it.[7] Each full-duplex channel has two frequency assignments. Duplex channels can be used to place calls over the public telephone network for a fee via a marine operator. When full-duplex is used, the call is similar to one using a mobile phone or landline. When half-duplex is used, voice is only carried one way at a time and the party on the boat must press the transmit button only when speaking. This facility is still available in some areas, though its use has largely died out with the advent of mobile and satellite phones. Marine VHF radios can also receive weather radio broadcasts, where they are available.
The accepted conventions for use of marine radio are collectively termed "proper operating procedure". These international conventions include:
Stations should listen for 30 seconds before transmitting and not interrupt other stations.
Maintaining a watch listening on Channel 16 when not otherwise using the radio. All calls are established on channel 16, except for distress working switch to a working ship-to-ship or ship-to-shore channel. (procedure varies in the U.S. only when calls can be established on Ch. 9)
During distress operations silence maintained on ch. 16 for other traffic until the channel is released by the controlling station using the pro-word "Silence Fini". If a station does use Ch. 16 during distress operations controlling station issues the command "silence mayday".
Using a set of international "calling" procedures such as the "Mayday" distress call, the "Pan-pan" urgency call and "Sécurité" navigational hazard call.
Using "pro-words" based on the English language such as Acknowledge, All after, All before, All stations, Confirm, Correct, Correction, In figures, In letters, Over, Out, Radio check, Read back, Received, Say again, Spell, Standby, Station calling, This is, Wait, Word after, Word before, Wrong (local language is used for some of these, when talking to local stations)
Using the NATO phonetic alphabet: Alfa, Bravo, Charlie, Delta, Echo, Foxtrot, Golf, Hotel, India, Juliett, Kilo, Lima, Mike, November, Oscar, Papa, Quebec, Romeo, Sierra, Tango, Uniform, Victor, Whiskey, X-ray, Yankee, Zulu
Using a phonetic numbering system based on the English language or a combination of English and Roman languages: Wun, Too, Tree, Fow-er, Fife, Six, Sev-en, Ait, Nin-er, Zero, Decimal; alternatively in marine communication: unaone, bissotwo, terrathree, kartefour, pantafive, soxisix, setteseven, oktoeight, novenine, nadazero
In 2022, the ETSI issued a proposal for implementing the use of FDMA protocols on the band in response to increasingly scarce availability of voice channels in some circumstances owing to the widespread use of systems such as AIS. The plan includes significantly narrower 6.25kHz channel spacing, and would support voice and data applications.[15]
Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter. Frequencies immediately below VHF are denoted high frequency (HF), and the next higher frequencies are known as ultra high frequency (UHF).
Sécurité is a procedure word used in the maritime radio service that warns the crew that the following message is important safety information. The most common use of this is by coast radio stations before the broadcast of navigational warnings and meteorological information.
An emergency position-indicating radiobeacon (EPIRB) is a type of emergency locator beacon for commercial and recreational boats, a portable, battery-powered radio transmitter used in emergencies to locate boaters in distress and in need of immediate rescue. In the event of an emergency, such as a ship sinking or medical emergency onboard, the transmitter is activated and begins transmitting a continuous 406 MHz distress radio signal, which is used by search-and-rescue teams to quickly locate the emergency and render aid. The signal is detected by satellites operated by an international consortium of rescue services, COSPAS-SARSAT, which can detect emergency beacons anywhere on Earth transmitting on the distress frequency of 406 MHz. The satellites calculate the position or utilize the GPS coordinates of the beacon and quickly passes the information to the appropriate local first responder organization, which performs the search and rescue. As Search and Rescue approach the search areas, they use Direction Finding (DF) equipment to locate the beacon using the 121.5 MHz homing signal, or in newer EPIRBs, the AIS location signal. The basic purpose of this system is to help rescuers find survivors within the so-called "golden day" during which the majority of survivors can usually be saved. The feature distinguishing a modern EPIRB, often called GPIRB, from other types of emergency beacon is that it contains a GPS receiver and broadcasts its position, usually accurate within 100 m (330 ft), to facilitate location. Previous emergency beacons without a GPS can only be localized to within 2 km (1.2 mi) by the COSPAS satellites and relied heavily upon the 121.5 MHz homing signal to pin-point the beacons location as they arrived on scene.
A radiotelephone, abbreviated RT, is a radio communication system for conducting a conversation; radiotelephony means telephony by radio. It is in contrast to radiotelegraphy, which is radio transmission of telegrams (messages), or television, transmission of moving pictures and sound. The term is related to radio broadcasting, which transmit audio one way to listeners. Radiotelephony refers specifically to two-way radio systems for bidirectional person-to-person voice communication between separated users, such as CB radio or marine radio. In spite of the name, radiotelephony systems are not necessarily connected to or have anything to do with the telephone network, and in some radio services, including GMRS, interconnection is prohibited.
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.
Digital selective calling (DSC) is a standard for transmitting predefined digital messages via the medium-frequency (MF), high-frequency (HF) and very-high-frequency (VHF) maritime radio systems. It is a core part of the Global Maritime Distress Safety System (GMDSS).
A two-way radio is a radio transceiver, which is used for bidirectional person-to-person voice communication with other users with similar radios, in contrast to a broadcast receiver, which only receives transmissions.
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 to by its equivalent wavelength, 600 meters, or, using the earlier frequency unit name, 500 kilocycles or 500 kc.
A Maritime Mobile Service Identity (MMSI) is effectively a maritime object's international maritime telephone number, a temporarily assigned UID issued by that object's current flag state.
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 used. AIS information supplements marine radar, which continues to be the primary method of collision avoidance for water transport. Although technically and operationally distinct, the ADS-B system is analogous to AIS and performs a similar function for aircraft.
Maritime mobile amateur radio is an amateur radio transmission license that allows maritime operators to install and use radio while at sea. The operator's call sign is extended by adding the suffix "/MM" when transmitting at sea.
A land mobile radio system (LMRS) is a person-to-person voice communication system consisting of two-way radio transceivers which can be stationary, mobile, or portable.
2182 kHz is a radio frequency designed exclusively for distress calls and related calling operations in the maritime service.
An international distress frequency is a radio frequency that is designated for emergency communication by international agreement.
Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves. They are received by another antenna connected to a radio receiver. In addition to communication, radio is used for radar, radio navigation, remote control, remote sensing, and other applications.
An AIS-SART is a self-contained radio device used to locate a survival craft or distressed vessel by sending updated position reports using a standard Automatic Identification System (AIS) class-A position report. The position and time synchronization of the AIS-SART are derived from a built in GNSS receiver . Shipboard Global Maritime Distress Safety System (GMDSS) installations include one or more search and rescue locating devices. These devices may be either an AIS-SART, or a radar-SART.
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. Civil and military organisation's 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.
The Automatic Transmitter Identification System (ATIS) is a marine VHF radio system used and mandated on navigable inland waterways in Europe for identifying the ship or vessel that made a radio transmission. The identity of the vessel is sent digitally immediately after the ship's radio operator has finished talking and releases their transceiver's push-to-talk button. This contrasts to the Automatic identification system(AIS) used globally on ships that transmit continuously. A short post-transmission message is sent by the radio with the vessel identity and is in the form of an encoded call sign or Maritime Mobile Service Identity, starting with number "9" and the three country-specific maritime identification digits.
Very high frequency (VHF) survival craft transceivers (SCTs) are lightweight, portable, two-way, handheld VHF transceivers capable of radiotelephone on-scene communication between rescue units and the survival craft. Essentially these are hand-held VHF radios that are used in any survival craft, such as a life boat or life raft. SCTs with re-chargeable type batteries may be used for on-board communications as well.
An emergency locator beacon is a radio beacon, a portable battery powered radio transmitter, used to locate airplanes, vessels, and persons in distress and in need of immediate rescue. Various types of emergency locator beacons are carried by aircraft, ships, vehicles, hikers and cross-country skiers. In case of an emergency, such as the aircraft crashing, the ship sinking, or a hiker becoming lost, the transmitter is deployed and begins to transmit a continuous radio signal, which is used by search and rescue teams to quickly find the emergency and render aid. The purpose of all emergency locator beacons is to help rescuers find survivors within the so-called "golden day", the first 24 hours following a traumatic event, during which the majority of survivors can usually be saved.
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