What is channel 16 used for in marine radio?

Channel 16 (156.800 MHz) is the international calling and distress channel on marine VHF. It is used for making first contact and for distress, urgency, and safety calls. After that, you switch to a working channel for the actual conversation.

What is DSC in marine radio?

DSC stands for Digital Selective Calling. A DSC distress alert is sent at the push of a button over channel 70 and automatically transmits your identity (MMSI) and, if GPS is connected, your position. It is the digital precursor to the voice link.

What do MAYDAY, PAN PAN, and SECURITE mean?

They are the three levels of urgency in voice radio: MAYDAY for a distress with danger to life or vessel, PAN PAN for an urgency message without immediate danger to life, and SECURITE for safety messages such as weather or navigation warnings.

Do I need a radio license to transmit?

Yes. For marine radio you usually need the SRC, and for inland radio the UBI. In a genuine emergency, however, anyone on board may use the radio to call for help, even without a certificate.

Marine Radio Basics for Beginners

A VHF radio is your most important tool on the water for calling help quickly in an emergency and for communicating with other vessels, locks, and harbors. For beginners, marine radio often feels confusing: many channels, abbreviations like DSC and MMSI, plus fixed procedures for distress calls. This article explains the key basics so you understand how radio works on board and what really matters.

Why a Radio on Board Matters So Much

There is no emergency call box on the water, and often no reliable mobile phone coverage. The VHF radio therefore remains the central safety tool on board. Its big advantage: a distress call is heard not only by a coast radio station but by every vessel within range. In an emergency, the nearest boat can help long before a rescue cruiser arrives.

It is worth knowing that VHF works line of sight, meaning roughly as far as the sightline between the antennas reaches. Range therefore depends heavily on antenna height. A handheld radio only reaches a few nautical miles, a fixed antenna at the masthead considerably further. For typical coastal boating, VHF is usually plenty; for long offshore passages, you need other systems.

Marine Radio and Inland Radio: Two Separate Worlds

Before we get to channels, a fundamental distinction: marine (sea) radio and inland waterway radio are two separate radio services with their own rules, channels, and certificates. For marine radio you usually need the SRC, for inland radio the UBI. Both are independent qualifications, separate from the Sportbootführerschein (the German recreational boating license). Which certificate suits your area is covered in detail in our article UBI or SRC.

This post focuses on the basics of marine VHF, because that is where DSC and the internationally standardized distress procedures matter most. Much of it will also help you make sense of inland radio.

The Most Important VHF Channels

Marine VHF is divided into channels, each serving fixed purposes. For a start, you mainly need to remember two:

Channel 16 (156.800 MHz): the international calling and distress channel. You use it to make first contact and to transmit distress, urgency, and safety messages by voice. Channel 16 is not a chat channel: after first contact, you switch to a working channel for the actual conversation.
Channel 70: the channel for DSC, Digital Selective Calling. It carries the digital distress alert and digital calls. You do not talk on channel 70; it only transmits digital data.

On top of that come working channels for ship-to-ship conversations, area and harbor channels for communicating with locks, bridges, and harbor masters, and channels for coast radio stations. Which channels apply in your area is listed in the official documents and area information. The exact channel allocation is part of radio training and the respective question catalog.

DSC: The Digital Distress Call at the Push of a Button

Most modern marine radios support DSC (Digital Selective Calling). With it, a distress call can in principle be triggered at the push of a button. The radio then automatically sends a digital distress alert over channel 70 that contains your identity (MMSI) and, if a GPS is connected, your position.

The MMSI (Maritime Mobile Service Identity) is a nine-digit number that uniquely identifies your radio station, comparable to a phone number for your boat. It has to be applied for in advance and entered into the radio.

The sequence in an emergency: first you trigger the DSC distress alert (digital alert over channel 70), then you additionally make a voice distress call on channel 16. This way you combine the automatic, precise alerting with the direct voice link. This exact order is also practiced in the practical radio exam.

The Three Levels of Urgency: MAYDAY, PAN PAN, SECURITE

In voice radio there are three fixed signal words that clearly mark the urgency of a message. They are internationally standardized and each spoken three times:

MAYDAY – the distress call. Used when a vessel or person is in immediate danger and needs help at once, for example fire on board, collision, sinking, or a life-threatening medical emergency.
PAN PAN – the urgency message. It concerns the safety of a vessel or person without immediate danger to life, for example loss of maneuverability without acute danger.
SECURITE (pronounced “say-cure-e-tay”) – the safety message. It announces important navigation or weather warnings, such as gale warnings or notices of hazards.

This ranking ensures that everyone listening immediately knows how serious a message is. A MAYDAY always has absolute priority over any other radio traffic. For how to attract attention beyond the radio in an emergency, see our article on distress signals at sea.

How a Simple Call Works

A normal call follows a clear pattern. You call the other station on the calling channel (or via DSC), stating their name first, then your own, and propose a working channel. After confirmation, both sides switch to that working channel and handle the conversation there. That keeps the calling channel free for others.

So that everyone understands each other, the international phonetic alphabet is used for spelling (Alfa, Bravo, Charlie, and so on). International marine radio is also conducted in English, which is why the SRC exam includes an English component. Detailed example dialogues go beyond this overview, but they are part of any good radio preparation.

The Key Rules of Radio Discipline

Radio is a shared medium: only one station can transmit on a channel at a time. So a few fixed ground rules apply:

Keep it short and clear. Think first, then transmit. Long monologues block the channel for others.
Keep a listening watch: anyone underway with a radio should monitor channel 16 where possible. Commercial shipping is required to.
Keep channel 16 clear: no small talk, no tests on the distress channel.
No misuse: a false distress call is a criminal offense and ties up rescue services needed elsewhere.
A certificate is required: for regular radio operation you need a valid radio certificate (SRC or UBI). The only exception is a genuine emergency: in an acute distress, anyone on board may use the radio to call for help.

Conclusion

Marine radio is not rocket science once you know the basics: channel 16 is the calling and distress channel, channel 70 carries the digital DSC alert, and MAYDAY, PAN PAN, and SECURITE mark the three levels of urgency. DSC makes the distress call fast and precise, but does not replace the voice distress call on channel 16. Once you understand these building blocks, you can use the radio confidently day to day and respond correctly in an emergency. For regular operation you need the right certificate, but in a genuine emergency all that counts is that help arrives.

The Boatpass app helps you prepare for the SRC and UBI with the complete official question catalogs, a realistic exam mode, and targeted mistake training, so that you have channels, DSC, and the distress procedures down cold before you pick up the microphone yourself.

Marine Radio Basics: Channels, DSC and Distress Calls