Global Maritime Distress and Safety System (GMDSS)
Radical changes have taken place in VHF technology over the last 5 years. New Digital Selective Calling (DSC) equipment allows distress messages to be sent automatically, providing a pin-point location and nature of the distress. Coastguards will no longer have to keep a listening watch on CH16 and the technology will also allow messages to be sent on an intership basis.
The UK has adopted the stringent standards of Class D DSC: these involve having a dedicated DSC ‘controller’ which forms part of the VHF installation and is capable of sending and receiving digital messages.
DSC is the route to the future and provides some enhanced VHF features such as direct dial telephone contact, advanced messaging and message forwarding – effectively increasing the VHF range due to the digital nature of the information being transmitted.
With this equipment, lifting the ‘lid’ of the distress button and pressing it for four seconds will cause the distress alert to be transmitted. If in a panic situation, keeping the button pressed for a long time will result in an ‘undesignated’ distress alert to be sent which will still contain your MMSI (your vessel’s allocated identity number) your position in lat/long, the date and time.
When the alert has been transmitted, the receiver remains tuned to CH 70 awaiting a distress acknowledgement, also sent digitally form a shore station. If no such acknowledgement is received, the distress message will continue to be transmitted.
All DSC VHF radios within range will be warned both visually and audibly that a distress alert is in progress and the transmitted message will be displayed on the controller.
When it is acknowledged, the VHF will retune to channel 16 automatically enabling direct speech contact with the controlling station to be established. Similar actions as described above will occur when a vessel is fitted with satellite communications (type A, B or C only, culminating with direct data or voice communication to the Maritime Rescue and Coordination Centre (MRCC).
What other equipment forms part of the GMDSS?
406 MHz EPIRB’s (Emergency Position Indicating Radio Beacons). When activated, on or more of the four COPAS-SARSAT satellites will pinpoint your position. To aid the vessel identification, the EPIRB serial number should have been pre-programmed into the EPIRB, which must have been registered with the MCA at Falmouth.
SART’s (Search and Rescue Transponders). When switched on, all radars within about 5 miles will show a series of ‘blips’ on their screens, emanating from your location.
Navtex receivers are dedicated to receiving safety information such as navigation, gale warnings and weather forecasts displayed as text.
All marine VHF, MF and HF radios require the user and the vessel to hold a relevant licence.
The vessel’s licence is like a car tax disc, but it is also the key to obtaining an MMSI number which will uniquely identify your vessel. You can obtain an application form for a ship’s radio OFCOM from this link to OFCOM. You can also obtain an application form for a transportable licence using this link.
The user requires an operator’s licence and two different types are available. For VHF only the SRC (Short Range Certificate) is available. VHF operation itself is fairly straightforward and training, covering radio etiquette and procedures, takes one day. It also teaches the user about the relatively recent advent of digital selective calling (DSC) functions and new emergency procedures.
For other communications the LRC (Long-Range Certificate) is required. This covers procedures, such as setting up an HF call, and takes three or four days.
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