Radio Survey

Emergency Position Indicating Radio Beacons (EPIRBs) are small, portable, battery powered radio transmitters that are both watertight and buoyant and transmit in the 406.0 – 406.1 MHz channel. EPIRBs are carried aboard merchant ships, some private vessels, commercial and military aircraft. They also transmit a distinctive swept audio tone signal on the international aeronautical distress frequencies of 121.5 MHz for homing purposes by search and rescue aircraft. Aircraft at 30 000 feet can detect the audio tone signals at approximately 200 n miles.

EPIRBs are tracking transmitters which aid in the detection and location of boats, aircraft, and people in distress. A PLB (personal locator beacon) is particular type of EPIRB that is typically smaller, has a shorter battery life and unlike a proper EPIRB is registered to a person rather than a vessel. The terms ELB (emergency locator beacon) and ELT (emergency locator transmitter) are used interchangeably with EPIRB only when used on aircraft. Strictly, they are radiobeacons that interface with worldwide offered service of Cospas-Sarsat, the international satellite system for search and rescue (SAR). When manually activated, or automatically activated upon immersion or impact, such beacons send out a distress signal. The signals are monitored worldwide and the location of the distress is detected by non-geostationary satellites doppler trilateration and in more recent EPIRBs also by GPS.

The basic purpose of a distress radiobeacon 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.

Equipment requirements for GMDSS vessels vary according to the area (or areas) in which a ship operates. Coastal vessels, for example, only have to carry minimal equipment if they do not operate beyond the range of shore based VHF stations (Sea Area A1). Ships which trade further from land are required to carry MF equipment in addition to VHF (sea area A2). Ships which operate beyond MF range are required to carry HF and/or Inmarsat equipment in addition to VHF and MF (sea areas A3 and A4).

Every GMDSS ship is required to carry the following minimum equipment (as de ned by SOLAS Chapter IV, regulation 7):

- A VHF radio installation capable of transmitting DSC on channel 70, and radiotelephony on channels 16, 13 and 6; 

- A SART (Two on vessels over 500 GRT, one on vessels 300 - 500 GRT); 

- A NAVTEX receiver, if the ship is engaged on voyages in any area where a NAVTEX service is provided; 

- An Inmarsat EGC receiver, if the ship is engaged on voyages in any area of Inmarsat coverage where MSI services are not provided by NAVTEX or HF NBDP; and 

- A 406 MHz EPIRB. Vessels trading exclusively in sea area A1 may t a VHF DSC EPIRB in lieu of a 406 MHz EPIRB). 


Every passenger ship shall be provided with means of two-way on-scene radio-communications for search and rescue purposes using the aeronautical frequencies 121.5 MHz and 123.1 MHz from the position from which the ship is normally navigated. 


The carriage requirements for the various GMDSS sea areas are de ned in the following regulations taken from SOLAS Chapter IV. Detailed guidelines when implementing new GMDSS installations on board SOLAS ships should be referred to COMSAR/Circ.32. 


IMO – the International Maritime Organization – is the United Nations specialized agency with responsibility for the safety and security of shipping and the prevention of marine pollution by ships.

The first tries to commonly regulate shipping and navigation were made in 1914 after the Titanic disaster. Inter-Governmental Maritime Consultative Organization or IMCO (the name of IMO until 1982) was formed to fulfill a desire to bring the regulation of the safety of shipping into an international framework, for which the creation of the United Nations provided an opportunity.

When IMCO began its operations in 1958 certain other pre-existing instruments were brought under its aegis, most notable the International Convention for the Prevention of Pollution of the Sea by Oil (OILPOL) 1954. Throughout its existence IMCO, renamed the IMO in 1982, has continued to produce new and updated instruments across a wide range of maritime issues covering not only safety of life and marine pollution but also encompassing safe navigation, search and rescue, wreck removal, tonnage measurement, liability and compensation, ship recycling, the training and certification of seafarers, and piracy. More recently SOLAS has been amended to bring an increased focus on maritime security through the International Ship and Port Facility Security (ISPS) Code. The IMO has also increased its focus on air emissions from ships.

IMO is a specialized agency of the United Nations, and it is the international standard-setting authority for the safety, security and environmental performance of worldwide shipping. Its main purpose is to adjust fair and effective regulatory framework for the shipping industry that should be universally adopted and universally implemented.

The International Convention for the Safety of Life at Sea (SOLAS) is an international maritime agreement which requires Signatory flag states to ensure that ships flagged by them comply with minimum safety standards in construction, equipment and operation. The current version of the SOLAS Convention is the 1974 version, known as SOLAS 1974, which came into force on 25 May 1980. As at March 2016, SOLAS 1974 has 162 contracting States, which flag about 99% of merchant ships around the world in terms of gross tonnage.

Amendments to the 1974 SOLAS Convention concerning radiocommunications for the GMDSS were published in 1989 and entered into force on 1 February 1992. 

All ships over 300 gross tonnage (GRT) on international voyages, and hence subject to the 1974 SOLAS Convention, have been required to comply with the carriage requirements of the GMDSS since 1 February 1999. 

The carriage requirements for ships subject to the SOLAS Convention, or voluntarily GMDSS equipped are contained in Chapter IV of SOLAS with amplifying advice provided in AMSA Marine Order 27 (Radio Equipment) 2009. Some requirements (e.g. for SAR locating devices) are also contained in Chapter III of SOLAS, the International Life-Saving Appliance (LSA) Code, and the High Speed Craft (HSC) Code. For vessels not subject to the SOLAS Convention but are required to be GMDSS ‘compatible’ by Commonwealth legislation the carriage requirements are contained in Appendix 6 AMSA Marine Order 27 (Radio Equipment) 2009. The carriage requirements for both GMDSS compliant and GMDSS compatible ships are designed to ensure the vessel can meet the functional requirements of the GMDSS relevant to that vessel and its operating area/s. 

The Global Maritime Distress and Safety System (GMDSS) is a globally accepted and adopted set of rules protocols and prescriptions, which assure safety navigation and shipping. The GMDSS equipment is applied to increase safety and make it easier and faster to rescue distressed ships, boats and aircrafts. The GMDSS enables a ship in distress to send an alert using various radio systems. Thanks to this system the alerts has a very high contingency to be received by either shore rescue authorities and/or other vessels in the area.

Since the invention of radio at the end of the 19th century, ships at sea have relied on Morse code, invented by Samuel Morse and first used in 1844, for distress and safety telecommunications. But this mean appeared difficult and not reliable enough to assure the safety at sea in full volume.

So the International Maritime Organization (IMO), a United Nations agency specializing in safety of shipping and preventing ships from polluting the seas, began looking at ways of improving maritime distress and safety communications.

A new system, gone to rely on means of satellite and on-land radio services, besides, it has changed international distress notifications from ship-to-ship based to ship-to-shore (Rescue Coordination Center) based. The GMDSS assures capability of vessels of automatically distress alerting and locating for the cases where there is no time to send an SOS or MAYDAY call. And, for the first time, the system requires ships to receive broadcasts of maritime safety information that could prevent a distress, which became a primary target. In 1988, IMO amended the Safety of Life at Sea (SOLAS) Convention, requiring ships subject to it obligatory fit GMDSS equipment. Such ships were required to carry NAVTEX and satellite EPIRBs by August 1, 1993, and had to fit all other GMDSS equipment by February 1, 1999. US ships were allowed to apply GMDSS in lieu of Morse telegraphy equipment by the Telecommunications Act of 1996.

The GMDSS has introduced new technology which has completely transformed maritime radio-communications. The new system enables a distress alert to be transmitted and received automatically over long range, with a signi cantly higher reliability.