Range · Equipment · Offshore safety
Marine VHF is immediate, familiar and extremely useful—but it is not a universal offshore lifeline. Understanding its physical and operational limits is part of using it responsibly.
VHF is built for nearby communication
Marine VHF normally propagates by radio line of sight. Range depends strongly on the height of both antennas, surrounding terrain and the installation—not simply the wattage printed on the radio. A handheld at cockpit height and a fixed set connected to a masthead antenna do not have the same practical reach.
What DSC adds
Digital Selective Calling can transmit a structured alert including vessel identity and, when the radio has valid GNSS data, position. It improves alerting; it does not repeal the range limits of VHF. A disconnected or stale position source can leave an alert without useful current coordinates.
Reliable communication is not measured by how much was transmitted, but by what the receiving side can understand and act upon.
What happens beyond VHF coverage
Offshore, reliable communication may require equipment designed for longer range: MF/HF, recognised GMDSS satellite services or a properly registered 406 MHz beacon, depending on vessel, voyage and applicable requirements. These systems do different jobs; an EPIRB alerts and identifies but is not a normal two-way conversation.
The useful question
Do not ask only whether a radio works at the marina. Ask who can receive it along the intended route, at what antenna height, and what independent method remains when the vessel moves beyond that coverage.
