In the 1980s, the International Maritime Organisation (a United Nations body) began developing the Global Maritime Distress and Safety System (GMDSS) to bring shipping out of the Portishead Radio world and into the world of satellite-based communications.
Much of this applies to commercial shipping and does not concern recreational vessels, but there is one piece of GMDSS equipment which anyone interested in offshore sailing will know about – the 406 MHz Emergency Position-Indicating Radio Beacon (EPIRB), designed to operate with the Cospas-Sarsat satellite system. This transmits emergency signals to Mission Control Centres which then co-ordinate appropriate search-and-rescue activities. (The change from pre-satellite mode, where a vessel in distress contacted the nearest shore station or passing ship – and the resulting end of the need to maintain human radio listening watches – is a defining characteristic of GMDSS).
One other component of GMDSS is Digital Selective Calling (DSC) capability on MF, HF and VHF maritime radios. A DSC-capable radio can be allocated a unique 9-digit identifier called a Maritime Mobile Service Identity (MMSI), like a telephone number. The DSC system allows a DSC-capable radio to make and receive radio-telephone and radio-telex calls to any radio set within range that has an MMSI. Such calls can be made to a single MMSI, to a group of MMSIs, or to all stations within receiving distance.
DSC includes one other very valuable function, built on the radio-telex capabliity. It can automatically broadcast a standard-format emergency alert, which can include position information taken from a connected GPS. This isn’t a substitute for making a distress call in the normal way, because it doesn’t say what the emergency is – all the DSC radio knows is that someone hit the red panic button – but it does mean you can send a distress call with a position signal even if you daren’t hang around waiting to contact someone and explain your woes in detail.
Does you VHF set have a red panic button? If so, go to Brad Hampton’s excellent article on yachtpals.com to find out how to set up your DSC facility and check that it works. If not, think seriously about replacing your radio.
Once you’ve set up your MMSI, you have also set yourself up a way of chatting to your friends. And no-one will mind – GMDSS encourages mariners to use DSC equipment for routine as well as emergency use.
