GMDSS system overview, sea areas A1–A4, and carriage requirements for vessels operating in Sea Area A1
This domain tests whether you can place a vessel in the correct GMDSS sea area, state the minimum radio equipment for Sea Area A1, and recognize the limits of the Restricted GMDSS Radio Operator (RG) license. The exam expects definitions and equipment logic, not mileage rules of thumb.
Sea areas
- Sea Area A1 is the area within radiotelephone coverage of at least one VHF coast station in which continuous DSC alerting is available. It is defined by shore DSC coverage, commonly about 20 to 30 nautical miles, but the mileage is not the definition.
- A2 is outside A1 but within MF DSC coverage; A3 is outside A1 and A2 but within Inmarsat coverage; A4 is outside A1, A2 and A3, including the polar regions.
Carriage in A1
A SOLAS vessel operating only in A1 needs a VHF installation capable of DSC on channel 70 and radiotelephony on channel 16, with a continuous channel 70 DSC watch. It also carries a 406 MHz EPIRB, at least one SART, survival-craft two-way VHF radios, and a NAVTEX or EGC receiver for maritime safety information where the service is provided. A reserve source of energy is required. Equipment must be FCC type accepted, the ship must hold a ship station license, and the EPIRB must be registered.
The RG license
The Restricted GMDSS Radio Operator license authorizes operation of GMDSS radio installations on vessels in Sea Area A1 only. It is not a full GMDSS operator license and does not authorize MF/HF or Inmarsat operation in A2, A3 or A4. It also does not authorize maintainer-level repair.
Worked example
A 24-metre passenger vessel is certified for A1 only. It has a type-accepted VHF with DSC, a registered 406 MHz EPIRB, one SART, three survival-craft VHF radios and a NAVTEX receiver. The owner asks whether one RG can be the sole radio operator. The answer is yes for the A1 installation, provided the ship station license is valid and the equipment is type accepted, because the RG scope matches A1. The RG still may not operate an MF/HF installation for an A2 passage or perform maintainer repairs.
Traps that cost marks
Do not treat A1 as exactly 20 nautical miles; it is shore DSC coverage. Do not assume the RG license covers all GMDSS sea areas. Do not use channel 70 for voice. Do not confuse EPIRB registration with the ship station license.