Entry & progression
Certificate: the minimum radio qualification to operate a marine VHF/DSC radio. Required for any vessel with a fixed VHF and for the commercial endorsement of RYA/MCA certificates. Entry: none. Progresses to the GMDSS Restricted (ROC) and General (GOC) operator certificates.
VHF and Digital Selective Calling
Marine VHF is a line-of-sight radio, giving a range of roughly 20-30 miles ship-to-shore and less ship-to-ship, so its range depends on aerial height. Digital Selective Calling (DSC) is a digital layer that lets a radio send a pre-formatted alert — including a distress alert carrying the vessel's identity (its MMSI) and, if connected to GPS, its position — at the press of a button, which other DSC radios and coast stations receive automatically. This transformed distress alerting: instead of hoping someone hears a voice call, a DSC alert reaches everyone in range instantly with the who and where already in it.
- Every DSC radio has a unique MMSI (Maritime Mobile Service Identity) number identifying the vessel.
- Connect the radio to a GPS so that a DSC distress alert automatically carries the vessel's position.
- Channel 16 is the international distress, safety and calling channel, monitored by the coastguard.
- Use low power (1 W) for short-range working and high power (25 W) only when the range needs it.
WARNING — Guard the distress button The red DSC distress button sends a real distress alert to everyone in range and launches a rescue response. Keep the cover down and press it only in a genuine distress; a false alert wastes rescue resources and is an offence.
TIP — Connect the GPS and set the MMSI A DSC radio is only fully effective with its MMSI programmed and a GPS feed connected. Without the GPS a distress alert carries no position; without the MMSI it cannot identify the vessel.