Chapter IV - Radiocommunication and Radio Operators
What Chapter IV actually requires
Chapter IV certifies GMDSS radio personnel (Regulation IV/2) and leaves operational detail to the Radio Regulations. Only two STCW certificates matter:
- ROC (Restricted Operator's Certificate) – valid for Sea Area A1 only, i.e. within VHF DSC coverage of a shore station.
- GOC (General Operator's Certificate) – valid for A1, A2, A3 and A4.
A Long Range Certificate (LRC) is a voluntary or regional certificate and is not an STCW requirement; if an option offers the LRC as the correct answer for a GMDSS post, it is a trap.
Sea areas
A1 is VHF/DSC shore coverage; A2 adds MF; A3 is Inmarsat coverage roughly between 70°N and 70°S; A4 is everything else, requiring HF. A ship trading in A2 or A3 therefore needs at least one holder of a GOC - a ROC alone will not satisfy the requirement.
Equipment maintenance
At sea there are three acceptable methods: duplication of equipment, shore-based maintenance, or at-sea maintenance capability (an appropriately qualified person on board). A common trap is offering "no maintenance needed if the ship stays in A1".
Worked example
A vessel is certificated for A1, A2 and A3, and her only radio operator holds a ROC. She is not in compliance: the ROC covers A1 only, so the operator must upgrade to a GOC, or another crew member holding a GOC must be carried.
Rule of thumb: ROC = "coastal"; GOC = "global". Match the certificate to the highest sea area for which the ship is certificated.