GMDSS and radiocommunications: Chapter IV equipment and watchkeeping
What the exam tests
GMDSS questions test sea areas, carriage, and the radio watch. You need to link A1-A4 to the equipment that provides distress alerting, SAR coordination, locating, and maritime safety information.
Sea areas and carriage
A1 is within VHF coast-station coverage; A2 within MF; A3 within Inmarsat geostationary coverage; A4 outside A1-A3. Core equipment includes VHF DSC on channel 70, MF/HF DSC where required, Inmarsat or HF for A3, NAVTEX receiver, 406 MHz EPIRB, 9 GHz SART, and two-way VHF radiotelephone for survival craft. Battery capacity and source arrangements are part of the fit. The radio watch includes continuous DSC watch on VHF channel 70 and the applicable MF/HF distress frequencies, plus VHF channel 16. NAVTEX safety information is normally received on 518 kHz in English.
Worked example
A ship trades in A2. It needs VHF DSC and MF DSC capability, not just a VHF set. The 406 MHz EPIRB must be registered to the ship and its battery and hydrostatic release within service life. A SART is carried for locating, and the radio log records the daily, weekly and monthly checks. If the MF DSC watch is lost, the ship cannot simply rely on VHF; the failure is a GMDSS carriage or availability issue.
Traps
Do not treat a 121.5 MHz homing signal as the primary EPIRB alert. Do not place the SART on a different frequency from 9 GHz. Do not silence a DSC alarm without checking whether it is a distress or routine call. Do not record a test as passed if the coast station acknowledgement was not received.