Which VHF marine radio features should I consider for my boat?
I'm replacing the old fixed VHF on my 9-metre cruising boat, which we use for coastal trips and occasional overnight passages. Should I pay extra for built-in GPS and AIS, and would a handheld be enough as a backup?
Answer
For most coastal cruising boats, choose a 25W fixed VHF with Digital Selective Calling (DSC), a dependable GPS position source and controls you can reach from the helm. Give a sound aerial installation priority over extra display features, then consider AIS reception and a waterproof, floating handheld for backup.
Check the aerial installation
Before comparing radios, inspect the existing aerial, coaxial cable, connectors and power supply. Corroded plugs, waterlogged cable or a poor aerial can undermine even an expensive radio. Replacing the set alone will not cure those faults.
Marine VHF works mainly by line of sight, so aerial height makes a considerable difference. A sailing yacht normally benefits from a masthead aerial; a motorboat needs a suitable mounting point clear of obstructions. Check the bracket and cable route against the aerial manufacturer's instructions.
- Fixed sets: usually offer 25W maximum transmit power and a 1W setting for nearby traffic.
- Handheld sets: usually transmit at 5 to 6W, with a shorter aerial much closer to the water.
- Typical range: about 30 nautical miles for a well-installed fixed set and 3 to 5 nautical miles for a handheld. Range depends heavily on aerial heights, terrain and conditions.
Treat those distances as planning estimates, not guaranteed coverage. Disconnect the supply before wiring, and protect the radio circuit with the fuse specified by its manufacturer.
Prioritise DSC and GPS
DSC lets a correctly configured radio send a digital distress alert containing your identity and, when available, your position. Choose a recreational fixed set with Class D DSC and a protected distress button you can reach from your normal operating position.
The radio must have its assigned Maritime Mobile Service Identity (MMSI) programmed correctly. Check the procedure before buying second-hand: changing an existing MMSI may require a dealer reset. Radio licensing and operator qualification requirements depend on where the boat is registered and operated.
Built-in GPS reduces dependence on the chartplotter and its data connection. An internal GPS aerial may struggle below a metal deck or inside an enclosed console, so check whether the set supports an external GPS aerial.
If position comes from another instrument, check the connection type. NMEA 0183 and NMEA 2000 are different interfaces. Confirm that position and time appear on the radio; connected wiring does not guarantee working data.
Some GPS-equipped sets also show speed over ground, course over ground and waypoints. These provide useful backup functions, but course over ground shows your direction of travel, not necessarily where the bow points.