Equipment to be duplicated for area A3 vessels
GMDSS ships operating in A3 areas are required to provide the following duplicated equipment:
- Two complete VHF installations (including DSC), and either;
- Two complete Inmarsat C systems and one MF radio system, or;
- One complete Inmarsat C system and one complete MF/HF radio system (including a scanning DSC receiver and NBDP equipment).
Many GMDSS ships opt for the latter option (1 Inmarsat C and one MF/HF DSC system), on cost grounds. Unfortunately, this has proven to be one of the underlying causes of the present extremely high false alerting rate on some GMDSS systems.