GMDSS send messages on the HF and VHF bands using Digital Selective Calling (DSC). The system utilises a number of HF and VHF frequencies to provide global coverage. 2187.5 kHz 4207.5 kHz 6312.0 kHz 8414.5 kHz 12577.0 kHz 16804.5 kHz Ships at sea are required to monitor 2187.5 and 8414.5 but often monitor all of […]