A marine VHF radio is the most important communication tool on most sailboats. It lets you call for help, talk to other boats, contact marinas and bridges, and hear safety broadcasts and weather warnings. Unlike a cell phone, a VHF call on channel 16 is heard by every station in range at the same time, including the Coast Guard and the boats around you, which is exactly what you want in an emergency.

Quick answer: keep your VHF on channel 16 while under way, use it to make first contact, then move to a working channel to talk. Speak slowly, keep calls short and use standard procedure words. In a life-threatening emergency, press and hold the red DSC distress button (if your radio is connected to GPS and programmed with an MMSI), then make a Mayday voice call on channel 16.

Fixed vs Handheld VHF

Most cruising sailors carry both: a fixed radio as the primary set and a handheld as a backup and for the dinghy or life raft.

Feature	Fixed (installed) VHF	Handheld VHF
Transmit power	Up to 25 watts, switchable to 1 W	Typically up to 5 or 6 W
Antenna	Masthead or rail mount, much higher	Short antenna at head height
Typical range to another boat	Often 10–20+ nautical miles, depending on antenna height	Often only a few miles
Power source	Boat’s batteries	Own rechargeable battery
DSC and GPS	DSC standard on modern sets; GPS input or built-in GPS	Many have DSC and built-in GPS; check before buying
Best for	Primary communication and distress alerting	Backup, dinghy, abandon-ship bag, cockpit use

VHF is line-of-sight radio, so range depends mainly on antenna height (both yours and the station you are calling). Shore stations with tall antennas can often hear a fixed set much farther away than another small boat can. If your only antenna is at the masthead, consider an emergency antenna in case you lose the mast.

Key Channels and Their Uses

Channel allocations vary a little between countries, so check the list for your area (in the US, the Coast Guard Navigation Center publishes it; in the UK and Europe, almanacs and national authorities do). These are the ones every sailor should know:

Channel	Use
16	International distress, safety and calling. Monitor it whenever you are under way. Use it only to make contact and for emergencies, then switch.
70	Digital Selective Calling (DSC) only. Voice is not permitted; your radio listens to it automatically.
9	In the US, a secondary calling channel for recreational boats; used by many marinas.
13	In the US and some other areas, bridge-to-bridge navigation safety between ships. Useful for talking to a ship about a close-quarters situation.
22A	In the US, Coast Guard liaison and safety broadcasts (the Coast Guard will ask you to switch to it).
6	Intership safety; often used in search and rescue coordination.
Working channels	Ship-to-ship chat for recreational boats, for example 68, 69, 71, 72 and 78A in the US, or 6, 8, 72 and 77 in UK waters. Check local rules.
WX channels	In the US and Canada, continuous NOAA/Environment Canada weather broadcasts on receive-only channels. Elsewhere, coast stations announce weather on 16 and broadcast it on a working channel.

US channels with an “A” suffix (such as 22A) are simplex versions of international duplex channels. Most radios have a USA/International/Canada setting; make sure yours matches the waters you are in.

Radio Etiquette and Procedure Words

Good radio procedure keeps channels clear and messages understood. The basic rules:

• Listen before you transmit so you don’t talk over someone else.
• Press the transmit button, wait a moment, then speak clearly and a little slower than normal, with the mic a few inches from your mouth.
• Keep calls short. Channel 16 is for calling and emergencies, not conversations.
• Use low power (1 W) for short-range calls such as a marina or a nearby boat.
• Don’t use 16 for radio checks; many areas have an automated radio-check service on a working channel, or ask a marina.
• False distress calls are illegal and can be prosecuted. Profanity is not allowed.
• Use the phonetic alphabet (Alpha, Bravo, Charlie…) to spell names and call signs.

Common procedure words (prowords):

Proword	Meaning
This is	Precedes your boat name or call sign
Over	I have finished speaking and expect a reply
Out	End of conversation; no reply expected (never “over and out”)
Roger	I have received your last message
Say again	Please repeat
I spell	I am about to spell a word phonetically
Correction	I made a mistake; the correct version follows
Seelonce Mayday	Used by the station controlling a distress to impose radio silence
Mayday Relay	Passing on a distress message on behalf of another vessel

If you are new to boating terms in general, our list of common sailing terms is a good companion to this guide.

How to Make a Routine Call

Here is a typical call to another boat, called Seabird, from your boat, Blue Heron:

1. Check that channel 16 (or 9, where used) is clear.
2. Call: “Seabird, Seabird, Seabird, this is Blue Heron, Blue Heron. Over.“
3. They reply: “Blue Heron, this is Seabird. Over.“
4. Propose a working channel: “Seabird, this is Blue Heron. Go to channel 72. Over.” Once they confirm, switch.
5. On 72, call again briefly, have your conversation, and end with “Blue Heron, out.” Then return to channel 16.

If you get no answer, wait a couple of minutes before trying again. Many modern radios also let you make a DSC individual call to another boat’s MMSI, which rings their radio and moves both sets to a working channel automatically.

Mayday, Pan-Pan and Sécurité Calls

There are three levels of priority message. Know the difference and keep a printed card next to the radio so anyone aboard can make the call.

Mayday: grave and imminent danger

Use Mayday only when a vessel or person is in grave and imminent danger and needs immediate help: sinking, fire out of control, a person overboard who cannot be recovered, a life-threatening medical emergency. Send a DSC distress alert first if you can, then on channel 16, high power:

1. “MAYDAY, MAYDAY, MAYDAY.“
2. “This is Blue Heron, Blue Heron, Blue Heron” (plus call sign and MMSI if you have them).
3. “MAYDAY Blue Heron” (and call sign/MMSI).
4. Position: latitude and longitude, or a bearing and distance from a known landmark.
5. Nature of distress: “sinking,” “on fire,” “man overboard.”
6. Assistance required: “require immediate assistance.”
7. Number of people on board.
8. Other useful information: boat description, abandoning to life raft, life jackets on, EPIRB activated.
9. “Over.“

Then release the button and listen. If nobody answers, repeat the call. If you hear a Mayday from another vessel, write down the details, stay off the air, and respond only if the Coast Guard does not answer and you can help. If you are the only station hearing it, you may need to pass it on with a Mayday Relay.

Pan-Pan: urgent, but not immediately life-threatening

Use Pan-Pan for an urgent problem concerning the safety of the boat or a person, where there is no immediate danger to life: engine failure near a lee shore, a dismasting with nobody hurt, a crew member who needs medical advice (for example, prolonged vomiting and dehydration; see how to prevent seasickness). Format: “PAN-PAN, PAN-PAN, PAN-PAN. All stations, all stations, all stations. This is Blue Heron…” followed by position, the problem and the help required. A Pan-Pan can be upgraded to a Mayday if the situation worsens.

Sécurité: safety information

Pronounced “say-cure-ee-tay,” this prefix introduces navigation or weather safety information, such as a large floating hazard, a navigation light out, or a gale warning from a coast station. The announcement is made on 16, and the message itself is usually read on a working channel.

DSC and the Distress Button

Digital Selective Calling turns your VHF into a basic automatic distress beacon. When you press the red distress button (usually under a flip cover, held for several seconds), the radio sends a digital alert on channel 70 containing your boat’s identity and, if it is connected to GPS, your position. Coast stations and every DSC-equipped vessel in range receive it with an alarm. The radio then switches to channel 16 for your voice call.

Two conditions are essential for DSC to work properly:

• An MMSI must be programmed into the radio. Without one, many radios won’t send a distress alert at all, and rescuers can’t link the alert to your boat.
• A GPS position must be available. Connect the radio to your chartplotter or GPS (or choose a set with built-in GPS). Without a position, rescuers know who you are but not where you are.

Most radios let you choose the nature of distress (fire, sinking, man overboard and so on) before sending, but if time is short, just press and hold the button. If you send an alert by mistake, cancel it on the radio if it offers that function, and immediately call on channel 16 to tell the Coast Guard it was a false alert.

A VHF radio only reaches stations within line of sight. For offshore passages, it should be complemented by a satellite distress beacon. Our guide to EPIRB vs PLB explains the options.

Licensing and MMSI Basics

Rules differ by country, so check with your national authority. Two examples:

• United States: a recreational boat that is not required to carry a radio does not need an FCC ship station license to use VHF in US waters. If you sail to a foreign port (Canada, Mexico, the Bahamas and so on), you need an FCC ship station license and an operator permit. Recreational boaters who stay in US waters can get an MMSI free or at low cost from an authorized agent such as BoatUS; boats that travel abroad get one with their FCC license.
• United Kingdom: a vessel with a VHF needs an Ofcom Ship Radio Licence (free when applied for online), which also issues the MMSI and covers EPIRBs and PLBs. Whoever uses the radio needs an operator certificate, typically the RYA Short Range Certificate (SRC), or must be supervised by someone who holds one.

Elsewhere, most countries require both a station licence and an operator certificate, often the SRC or a national equivalent. If you charter abroad, the charter company’s radio will already be licensed, but you may be asked for an operator certificate.

Note that an MMSI belongs to the vessel (or, for some handhelds, the licence holder). Many radios only let you enter it once, after which a dealer has to reset it, so type it carefully.

Practise Before You Need It

• Read your radio’s manual and learn how to change channels, switch power, use dual-watch and send a DSC call.
• Show every crew member how to make a Mayday call, including from the helm while clipped on with a harness and tether; the skipper may be the person who needs help. Our man overboard recovery procedure includes when to send a distress alert.
• Tape a Mayday script, your boat’s name, call sign and MMSI next to the radio.
• Make a DSC test call to a friend’s MMSI, or use your radio’s test function, so you know it works.
• Keep the handheld charged and in a waterproof case, ready to grab. Add it to your list of must-have boat safety equipment and your cruising equipment essentials.

Summary

• Monitor channel 16 when under way; use it to make contact, then move to a working channel.
• Speak clearly, keep calls short and use standard procedure words.
• Mayday is for grave and imminent danger, Pan-Pan for urgent problems, Sécurité for safety information.
• DSC needs an MMSI and a GPS connection to be useful in an emergency.
• Licensing differs by country: check with the FCC, Ofcom or your national authority before you go.