Module 18 - Signals & Communications
Channel 70, Channel 16 and Working Channels
What you will learn
Select Channel 70, Channel 16, Channel 13 and a working channel by function, including known- and unknown-MMSI calling paths.
Channel choice follows the communication task. Channel 70 is DSC data only; Channel 16 carries distress and initial calling where required; detailed routine or urgency traffic moves to the appropriate working channel.
Channel 70 is reserved for DSC signalling and must not be used for voice. Channel 16 carries distress, urgency, very brief safety communications, and initial calling where the procedure requires it; routine conversations move promptly to a suitable working channel. Channel 13 is designated internationally for bridge-to-bridge navigational safety communication and may be useful when contact with another vessel cannot be established on Channel 16.
For a known vessel MMSI, an individual routine DSC call can nominate an inter-ship working channel. When the called set acknowledges, conduct the conversation on that selected channel. If the MMSI is unknown, the MCA small-craft guidance says to make a voice call on Channel 16 using low power initially and move to an inter-ship channel once contact is established; if there is no response, try Channel 13.
Calling a Coastguard or coast station by DSC is not the same as starting a long conversation on Channel 16. Make the appropriate individual call, accept the acknowledgement, ensure the set is on the channel indicated, and wait for the station to call. Harbour authorities publish their working channels and procedures; obtain them during appraisal and monitor before reaching the reporting point.
The skipper should prevent radio activity from becoming a navigation hazard. Prepare the message before keying the microphone, use the correct power, keep the helm and lookout informed, and avoid prolonged head-down menu operation near traffic or danger. If a call is not answered, reassess identity, channel, range, squelch, antenna, and urgency rather than filling Channel 16 with continuous repeats.
| Channel | Role | Do not |
|---|---|---|
| 70 | DSC signalling | Transmit voice |
| 16 | Distress, urgency announcement, safety/calling as required | Hold routine conversations |
| Working channel | Detailed voice traffic | Assume it without nomination/instruction |
| 13 | Bridge-to-bridge navigational safety | Treat it as general leisure traffic |
Call a vessel without blocking Channel 16
The skipper needs to contact a known vessel, then a second vessel whose MMSI is unavailable, while maintaining a crossing watch.
1. Known MMSI
Use an individual routine DSC call and nominate an appropriate inter-ship working channel.
2. Unknown MMSI
Call by voice on Channel 16 using low power initially, move once contact is made and try Channel 13 if there is no response as the MCA guidance describes.
3. Protect navigation
Prepare the call, keep the helm and lookout informed and avoid repeated head-down menu work near traffic.
Sense check: The crew can state which channel carries data, which makes contact and which carries the conversation.
Common mistake or limitation
- Never use Channel 70 for voice; it is reserved for DSC signalling.
- Channel 16 is not the place for an extended routine conversation after contact is made.
- Channel 13 supports bridge-to-bridge navigational safety communication; it is not a default leisure-chat channel.
- A channel sequence must not distract the operator from collision risk, lookout and vessel control.
Recap
- 70 — DSC data only.
- 16 — distress, urgency announcement, safety/calling functions as the procedure requires.
- Working channel — detailed conversation after contact or nomination.
- 13 — bridge-to-bridge navigational safety and the MCA unknown-MMSI fallback after no response on 16.
Optional quick check
Section 14 of 18
A routine individual DSC call to a known vessel nominates Channel 72 and is acknowledged. Where should the conversation occur?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
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