Module 4 - Channels & Frequencies
Channel 16
What you will learn
Decide when Channel 16 is the correct voice route, keep an initial call short, and move routine traffic away without losing the listening watch.
Channel 16 is the international VHF voice channel for distress, urgency, safety and initial calling. It protects access to help, so routine working traffic must move away promptly.
MCA small-craft guidance uses Channel 16 for the voice Mayday after a DSC distress alert, for an urgency announcement before moving to a nominated working channel, and for an initial voice call when the other vessel's MMSI is unknown. Those are different messages, but they share one discipline: identify the real priority before transmitting.
For a routine unknown-MMSI call, listen first, use low power initially, call briefly and agree an appropriate inter-ship channel once contact is made. Channel 16 is not the place for the resulting conversation, a marina booking, a radio check or social traffic.
After working traffic finishes, deliberately restore the required watch arrangement and confirm the displayed channel. A channel change that is not checked can leave an apparently powered radio listening somewhere unintended.
Call an unidentified yacht without occupying Channel 16
A yacht ahead is dragging a fender but you do not know its MMSI. There is no immediate danger and the channel is quiet.
1. Listen and classify
Confirm Channel 16 is clear and that this remains a brief routine ship-to-ship call, not distress, urgency or safety traffic.
2. Call briefly
Use low power first, name the called vessel, identify your own vessel and wait for a reply.
3. Move and restore
Agree an appropriate inter-ship channel, complete the useful exchange there, then restore the required watch.
Sense check: If the detailed conversation is still taking place on Channel 16, the channel move has not been completed.
Common mistake or limitation
- Treating Channel 16 as a general working channel merely because contact started there.
- Using the word safety to justify routine chatter instead of choosing the message's real priority and route.
- Moving to a working channel but forgetting to restore the required watch after the exchange.
Recap
- Channel 16 carries distress, urgency, safety and initial calling by voice.
- Routine calls must be brief and move to an appropriate working channel.
- Listen first, use low power initially for routine traffic and restore the watch afterward.
Optional quick check
Section 1 of 9
A routine unknown-MMSI call is answered on Channel 16. What is the next channel decision?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
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