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Radio communication facilities on board of vessels are a vital part of the safety equipment. It enables monitoring weather channels and communicating with other ships or coastal radio stations. All users of marine radio are responsible to conform to both national and international regulations and requirements.

The international administrations involved are the International Maritime Organization addressing general maritime safety issues and the International Telecommunication Union engaged in the technical details of communication hardware to ensure world wide compatibility of the equipment.

National telecommunication administrations are involved in the process of "Type Approval" of the radio communication equipment installed on board of ships and yachts. They are also authorized to issue the operating licenses required to operate marine radio.

International Maritime Organization

Under the scope of the SOLAS - GMDSS recommendations, the International Maritime Organization in London has specified the required radio equipment for commercial vessels. These recommendations are valid generally for all passenger vessels and all cargo ships over 300 gross tonnages on international voyages.

Specific equipment requirements for ships vary according to the sea area in which the ship operates. For this purpose the oceans are divided into four sea areas:

  • Area 1: coastal waters up to 30 Nm (in range of at least one coast station with VHF-DSC capability)
  • Area 2: coastal waters up to 150 Nm (in range of at least one coast station with MF-DSC capability)
  • Area 3: maritime areas covered by INMARSAT (Latitude from S 70° to N 70°)
  • Area 4: polar waters (HF range worldwide)
For all areas the following communication equipment is required (summary):
  • VHF radio with Digital Selective Call (DSC)
  • NAVTEX receiver (weather information by telex over radio)
  • EPIRB (Emergency Position Indicating Radio Beacon) to participate with the COMSAT-SARSAT Search and Rescue (SAR) system
  • Search-and-Rescue Radar transponder (SART)
  • VHF handheld radio

Vessels cruising in Area 2 waters will additionally carry MF/HF communication equipment (SSB) with DSC capability. SOLAS compliance for Area 3 requires satellite communication equipment (INMARSAT A or C). Vessels sailing in polar waters (Area 4) will carry special long-range HF-SSB radio with DSC capability.

Smaller ships and pleasure yachts are not required to have GMDSS equipment installed, including maritime radio, but they may be equipped by choice and can then participate in the GMDSS giving access to the global Search-and-Rescue facilities.

International Telecommunication Union

The International Telecommunication Union (ITU), headquartered in Geneva, Switzerland is an international organization within the United Nations Organization, where governments and the private sector coordinate global telecom networks and services. The regulations, resolutions and recommendations of the ITU and its decision boards on radio communication (ITU-R) are published in he international Radio Regulations. They cover both legal and technical issues, and serve as a supra-national instrument for the optimal world-wide management of the radio spectrum. For the allocation of frequencies and communication services, the world has been divided into three regions:

  • Region 1: includes roughly the area covered by Europe, Africa, the middle East and Russia
  • Region 2: includes the complete American continent and Greenland
  • Region 3: includes roughly the area covered by Australia and south and east Asia

This separation allows for flexible and optimal usage of the available frequency bands in each of the regions, but may result in incompatibilities between the regions on some radio channels. For this reason, equipment bought in one region may not fully comply to the regulations valid in the other regions. This should be taken into account, when cruising over the region boundaries.

The ITU has also allocated some dedicated radio frequencies for the purpose of marine communication. They cover the MF, HF and VHF radio bands. Due to the propagation characteristics of the electromagnetic radio waves, these different frequency bands are typically used as follows: MF and HF are well suited for long-range and even world-wide communication, whereas VHF radio can only be used for short-range communication.
div align="justify">In the VHF range, the ITU has established about 55 channels for marine purposes. Three of these radio channels are recognized worldwide for safety purposes:
  • Channel 13 (156.650 MHz) for intership navigation safety communication
  • Channel 16 (156.800 MHz) for distress, safety and calling communication
  • Channel 70 (156.525 MHz) for the Digital Selective Calling (DSC) service. Voice communication is not allowed on this channel!
Except for distress and safety purposes, the ITU has not allocated special services to these marine radio frequencies. The allocation of radio channels to certain marine services such as Vessel Traffic Control (VTS) or the port authorities is established by the national communication administrations. Therefore, there is no general international assignment of channels to services and although there is a widely accepted agreement on the usage of the different VHF channels, in many countries this assignment may not comply with national or local regulations (e.g. in port areas). It is the radio operator's responsibility to be informed on - and to comply to - the local radio regulations before radio transmissions are conducted.

For long-range communication, the ITU has allocated about 160 channels in different MF/HF frequency bands for marine radio. The channels are located in the 2-MHz MF band and the 4-, 6-, 8-, 12-, and 16-MHz HF bands. The calling and safety channels for initial contact with other stations or for emergency communication are at: 2182, 4125, 6215, 8291, 12290, and 16420 kHz using USB modulation.

Licenses and Permits for Communication Equipment

It is a legal requirement to have a ship's radio station license and marine radio operator's certificate before radio transmitting equipment is used on a yacht. The ship's radio license will document the vessel's international call sign and, if requested, also the 9 digit MMSI number to participate in the Digital Selective Calling network of GMDSS. Radio station call signs and MMSI numbers are internationally allocated. Call sign or MMSI number of a particular vessel may be obtained from the web site of the International Telecommunications Union (ITU).
div align="justify">To participate in nationally regulated communication networks, the radio equipment must be Type Approved by the national telecommunications authorities. This is documented in the license of the radio installation and also by the manufacturer in the delivery documents of the equipment.

In Europe, the following operating certificates for marine radio equipment with DSC capability can be obtained:
  • "Restricted Operator's Certificate" or "Short Range Certificate" valid only for VHF equipment
  • "General Operator's Certificate" or "Long-Range Certificate" valid for VHF, MF/HF and satellite communication equipment

International Radio Watch keeping Regulations

After the introduction of GMDSS, and its full deployment - for commercial vessels - since 1 February 1999, the compulsory watch keeping on the distress calling channels has been abolished. By adoption of IMO resolution MSC 77 (69), May 1998, the Maritime Safety Committee urges all governments to encourage seagoing vessels being voluntarily fitted with VHF radio equipment to be fitted also with facilities for transmitting and receiving distress alerts by DSC on VHF channel 70 no later than 1 February 2005.

Both the International Telecommunication Union and the International Maritime Organization have each established marine radio watch keeping regulations taking into account that not yet all vessels - especially pleasure boats - are equipped with GMDSS equipment. These regulations include to continue a voluntarily watch keeping on the traditional distress channels "where practicable".
Notice however, that national regulations may override this rule and may require to maintaining a watch on the distress channels whenever the radio is not being used to communicate and whenever the vessel is underway.


The most extended publication on maritime communication issues is the "Admiralty - List of Radio Signals" published by the United Kingdom Hydrographic Office. The complete work consists of 6 bands:
  • Band 1: Coast Radio Stations
  • Band 2: Radio Aids to Navigation, Satellite Navigation Systems, Legal Time, Radio Time Signals and electronic Position fixing Systems
  • Band 3: Maritime Safety Information Services (Weather, NAVTEX, ...)
  • Band 4: Meteorological Observation Stations
  • Band 5: Global Maritime Distress and Safety System
  • Band 6: Pilot Services, Vessel Traffic Services and Port Operations

Most bands are revised annually and can be kept up-to-date from the weekly "Admiralty Notices to Mariners". The price (as of 2008) is about 60 Euro per Band.

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