Marine VHF Radio: A Complete Guide
Press the transmit key on Channel 16 anywhere in the world and a coastguard operator, a tanker bridge officer and a dozen cruising sailors are listening within seconds. Marine VHF is the oldest piece of safety electronics on most boats, yet it remains the most reliable: it works when phones have no signal, it broadcasts to everyone within range at once, and a modern set with Digital Selective Calling can transmit your identity and GPS position in a single button press. The catch is that VHF only works well when everyone follows the same discipline — and that discipline is learned, not guessed.
How VHF actually works on the water
Marine VHF operates between 156 and 174 MHz and is strictly line-of-sight. From a masthead antenna 15 metres up, you can typically reach another yacht 10 to 15 nautical miles away and a coastguard station with a tall mast 30 to 40 miles out. A handheld set held at deck level might manage 3 to 5 miles. This is why a fixed set wired to a masthead antenna should always be your primary radio, with the handheld as a grab-bag backup. Most fixed sets transmit at 25 watts with a 1-watt low-power option; the rule is to use 1 watt for short-range conversations, such as calling a marina half a mile away, so you do not blanket the entire bay with your transmission.
Channel discipline: which channel does what
Channel 16 (156.8 MHz) is the international distress, safety and calling channel. You call another station on 16, then immediately agree a working channel and switch. Working a long social conversation on 16 is the fastest way to earn a public rebuke from the coastguard. Channel 13 is bridge-to-bridge navigation safety, used to arrange passing with commercial ships. Channels 6, 8, 72 and 77 are common ship-to-ship working channels. Marinas across the Mediterranean tend to listen on Channel 9 or a locally advertised channel; in the UK, marinas use Channel 80. Channel 70 is reserved exclusively for DSC digital signalling — never voice. Port operations, pilot stations and VTS (vessel traffic services) each publish their own channels in almanacs and on harbour charts, and calling them on the right channel first time marks you out as a competent skipper.
DSC and your MMSI: the red button explained
Digital Selective Calling transformed VHF in the 1990s. Every DSC set is programmed with a nine-digit MMSI number — effectively your boat's phone number — and connected to GPS. Lift the red cover, hold the distress button for five seconds, and the set transmits a digital burst on Channel 70 containing your MMSI, position and (if you selected one) the nature of distress. Every DSC-equipped vessel and coast station within range receives an alarm with your exact coordinates before you have spoken a word. The set then automatically switches to Channel 16 so you can follow up with a voice mayday. Two practical points: register your MMSI properly with your national authority so rescue services can look up your boat's description, and make sure the GPS feed is actually connected — a distress alert without a position loses most of its value.
The mayday call: word for word
A mayday is reserved for grave and imminent danger to vessel or life — fire, sinking, a crew member overboard and lost from sight, a medical emergency that threatens life. The script is fixed for a reason: rescuers extract information in a known order even from a panicked voice. On Channel 16, high power: say mayday three times, then this is followed by your boat name three times and your MMSI or callsign. Then the message, beginning with mayday once, boat name once, then position (read from the GPS as latitude and longitude, or as a bearing and distance from a charted point), the nature of distress, the number of people on board, and any other information such as liferaft deployment. End with over. If you hear no acknowledgement after about a minute, repeat. Practising this script aloud with crew during a calm passage feels silly for exactly five minutes and then becomes muscle memory.
Pan-pan and sécurité: the calls below mayday
Pan-pan (pronounced pahn-pahn) signals urgency without imminent danger to life: engine failure drifting toward a shipping lane, a serious but stable injury, dismasting in moderate weather. The structure mirrors a mayday — pan-pan three times, all stations or a specific coast station, identity, position, problem, assistance required. Sécurité (say-cure-ee-tay) is the safety call used for navigational warnings: a drifting container, a fishing net across a channel, or your own announcement before entering a blind, narrow passage. Coastguards use sécurité constantly for gale warnings, typically announced on 16 and broadcast on a working channel. Knowing the hierarchy means you never have to debate whether your situation is a mayday — if life or vessel is in grave and imminent danger it is; otherwise pan-pan covers you.
Routine calls without embarrassment
Most VHF use is mundane: calling a marina for a berth, arranging a bridge opening, contacting another yacht. The pattern is always the same. Call the station name twice, then this is and your boat name twice, then over. Wait. When they answer, propose or accept a working channel, switch, and keep it short. A typical marina exchange in Croatia or Greece lasts twenty seconds: berth request, boat length and draught, instructions for laid lines or a mooring buoy, finished. Common mistakes that mark a beginner: forgetting to release the transmit key while listening, saying over and out together (over invites a reply; out ends the conversation — they contradict each other), and calling on full power on a channel where everyone else is using low power.
Licences, exams and what the law requires
In most jurisdictions the radio itself needs a ship radio licence and the operator needs a certificate. In the UK and much of Europe that is the SRC (Short Range Certificate), a one-day course with exam covering everything in this article plus a practical assessment on a simulator. The USA does not require a licence for recreational VHF use in domestic waters, but US boats venturing abroad need an FCC ship station licence and restricted radiotelephone operator permit. Charter companies in Greece, Croatia and elsewhere routinely ask to see a VHF qualification alongside your skipper ticket. The course is genuinely worth the day: the DSC functions in particular are unintuitive until someone walks you through them on a live set.
Maintenance, range checks and antenna care
A VHF installation fails quietly. Corroded PL-259 connectors, a cracked antenna base or chafed coax in the mast can cut your effective transmit power by 90 percent while the set still receives nicely, so you never notice until you need it. Test transmit performance periodically with a radio check on a working channel (not 16) or, better, ask a marina or a nearby boat for a signal report from a known distance. Carry a spare emergency antenna that can be rigged at deck level if you are dismasted. Keep the handheld charged, ideally in a waterproof grab bag with the EPIRB. And update your MMSI registration when you sell the boat — search-and-rescue databases are full of stale entries that send rescuers looking for the wrong vessel.
Explore on the map
A radio is only half the picture; the other half is knowing which harbours, anchorages and coastguard regions surround you. Browse the interactive map to explore marinas and cruising destinations worldwide, check which stretch of coast you will be transmitting from next season, and plan passages where Channel 16 always has a friendly station within range.