Coverage, Antennas and a Communications Failure Plan

VHF is principally line of sight. Antenna height, terrain, vessel structure, sea state, transmitter power, cabling, and the receiving station affect range. A masthead fixed set usually reaches farther than a handheld close to deck level. The MCA's published A1 illustration assumes a vessel antenna four metres above sea level and explicitly notes that coverage is smaller for lower antennas and portable radios.

Check the installation before departure: the ship's call sign and MMSI match the licence and are programmed correctly, the GNSS position and time are current, the antenna and coaxial connections are sound, the handset can be reached, and the crew knows the controls. Test using an appropriate service without blocking a distress channel. Know whether the handheld is waterproof, charged, licensed for the intended operation, and stored where it remains available after flooding, fire, or dismasting.

Plan beyond the nominal range. Identify Coastguard coverage, harbour working channels, telephone or satellite alternatives, EPIRB or PLB provision, and how to alert another vessel. Keep essential numbers, MMSIs, call signs, and position formats accessible without the plotter. A mobile telephone can be useful but does not broadcast to nearby vessels and should not be treated as a complete substitute for marine distress communications.

When the fixed set fails, distinguish power, antenna, audio, data, and coverage faults. A powered display does not prove that the antenna path works. Try the independent handheld or backup power as appropriate, but do not let fault-finding distract from the vessel's immediate safety. Create sea room, send an alert while any path remains available, and brief a timed fallback: who retries, on which equipment, and what action follows if no contact is made.