Question 1

What is VHF Channel 16 used for, and what's the golden rule about using it?

Accepted Answer

Distress, safety and calling: you make brief contact here, then switch to a working channel for the actual conversation. Channel 16 is the international distress, safety and calling channel. Everyone monitors it, so you make brief initial contact there and immediately move to a working channel, keeping 16 clear for genuine emergencies.

Question 2

Your vessel is in grave and imminent danger and needs immediate help (sinking, fire, someone unconscious). Which call do you make?

Accepted Answer

Mayday, repeated three times, on Channel 16. "Mayday" (from the French "m'aidez", help me) signals grave and imminent danger to life or vessel. Say it three times on Channel 16 to cut through and make clear this isn't routine traffic.

Question 3

You have a man overboard but the situation, while urgent, isn't yet life-threatening (say, engine failure drifting toward rocks with time to act). What call fits?

Accepted Answer

Pan-Pan, repeated three times: signals urgency, one level below Mayday. "Pan-Pan" (repeated three times) signals urgency: a situation that needs help but isn't yet immediately life-threatening. A man overboard, especially once recovered or stable, is a textbook Pan-Pan situation if not full Mayday.

Question 4

You want to broadcast a navigational hazard warning (say, a partially submerged container spotted in a shipping lane). What's the correct prefix?

Accepted Answer

Sécurité, repeated three times, then the details on a working channel. "Sécurité" (repeated three times) flags a safety message (navigational hazards, severe weather warnings), important but not itself an emergency. Coast stations use it constantly for weather and hazard broadcasts.

Question 5

You're passing a moored fishing boat in a narrow channel and want to confirm which side to pass on. Which type of channel do you use?

Accepted Answer

A local working/hailing channel (e.g. Channel 9 or a port-specific channel), not Channel 16. Routine vessel-to-vessel or hailing traffic belongs on a designated working/hailing channel, not 16. Many harbours and marinas publish which channel they monitor: check local charts or pilot notes before you arrive.

Question 6

Why do sailors spell out boat names and call signs using words like "Alpha, Bravo, Charlie" instead of just saying the letters?

Accepted Answer

The NATO phonetic alphabet avoids letters (like B, D, P, T) that sound alike over noisy, low-quality radio audio. Over VHF's compressed audio and static, similar-sounding letters get confused constantly. The phonetic alphabet (Alpha, Bravo, Charlie…) removes that ambiguity so a boat name or position gets copied correctly the first time.

Question 7

What's the correct structure for a routine radio call to another vessel or a marina, before you start the actual conversation?

Accepted Answer

Say the called station's name up to three times, then "this is" and your vessel's name, then wait for a reply before continuing. The standard format is: "[Station being called], [Station being called], [Station being called], this is [your vessel name], over." This confirms who you're trying to reach before you commit airtime to the message itself.

Question 8

During an active Mayday from another vessel, what should you do if you're not the one responding to coordinate the rescue?

Accepted Answer

Maintain radio silence on that channel unless you can materially help, so the distress traffic isn't stepped on. Distress traffic takes absolute priority. Unless you can directly assist (nearby, relevant information, or asked to relay), stay off the channel so the vessel in distress and the coordinating station (often a coast guard) can communicate clearly.

Question 9

Modern VHF sets have a red button under a cover, wired to Channel 70. What does pressing it actually do?

Accepted Answer

Sends an automated Digital Selective Calling (DSC) distress alert carrying your vessel's identity and GPS position to all DSC-equipped stations and vessels in range. DSC distress alerting on Channel 70 sends your position and identity automatically the instant you press it: a huge advantage over a voice Mayday if you're injured, disoriented, or the situation develops too fast to talk.

Question 10

Your VHF set has a 9-digit MMSI number programmed into it. What is this number actually used for?

Accepted Answer

A unique identifier for your vessel, used by DSC distress alerts and automated systems to show who is calling. MMSI (Maritime Mobile Service Identity) is what makes a DSC distress alert on Channel 70 useful: rescuers instantly see which specific vessel is calling and, if it's linked to a registration, who to contact.

Question 11

VHF range is often quoted as roughly 20-30 nautical miles between two vessels, or more to a tall shore station. What mainly determines this, rather than raw transmitter power?

Accepted Answer

Line of sight: VHF signals travel in roughly straight lines, so range depends heavily on antenna height at both ends, not just wattage. This is why a handheld radio held at cockpit height has noticeably less range than the same power transmitted from a masthead antenna: get the antenna higher and you push the radio horizon further away.

Question 12

Different countries designate different secondary channels for general ship-to-ship chatter and local safety calling, alongside Channel 16. Why does it matter to check local usage before you arrive?

Accepted Answer

Working/hailing channel assignments can vary by region: using the wrong one may mean no one relevant hears you, or you occupy a channel reserved for something else. A pilot book or local chart usually states which channel a marina, port authority, or coast guard actually monitors: worth five minutes of checking before you arrive rather than guessing on approach.

Question 13

In a Mayday call, after saying "Mayday" three times and identifying your vessel, what should you give next, in a clear and logical order?

Accepted Answer

Your position, the nature of the emergency, the number of people aboard, and the kind of assistance you need. Position first, because that's what a rescuer needs even if the call gets cut off: then what's wrong, how many people are involved, and what you need. That order gets the most critical facts across even in a short or interrupted transmission.

Question 14

During a radio call, what does saying "over" at the end of your transmission actually communicate?

Accepted Answer

You've finished speaking and are now listening for a reply: it's the other station's turn to transmit. "Over" hands the conversation back; "out" (used instead, never together as "over and out") signals the exchange is genuinely finished and no reply is expected.

Question 15

You want to confirm your VHF radio is transmitting and receiving properly before leaving the dock. What's the correct way to test it?

Accepted Answer

Call a radio check on a working channel (not 16), asking a marina or another vessel to confirm they hear you clearly: never use Mayday to test equipment. A quick radio check on a working channel confirms both transmit and receive are working, without triggering the real emergency response a test Mayday would set off.

Question 16

You hear a Sécurité broadcast warning of a partially submerged shipping container in the area you're about to sail through. What should you actually do with that information?

Accepted Answer

Note the position, keep a sharper lookout in that area, and pass the warning on if you encounter other vessels who may not have heard it. Sécurité information is only useful if you actually act on it: a noted position and a sharper lookout cost nothing, and relaying it onward is exactly how word-of-mouth safety information is supposed to spread.

Word	Meaning	Example
Mayday	Grave and imminent danger to life or vessel	Taking on water, fire, person unconscious
Pan-Pan	Urgent, but not immediately life-threatening	Engine failure drifting toward danger, injured but stable crew
Sécurité	Safety information, not an emergency	Navigational hazard, severe weather warning

VHF Radio: Channels, Calls and Emergencies

Channels: 16 to call, a working channel to talk

The three distress prefixes

The phonetic alphabet

Making a routine call

If you hear a Mayday

VHF Radio: Channels, Calls and Emergencies quiz