Why is listening part of every radio call?
Listening avoids transmitting over existing traffic and helps build a picture of channel use. Set volume and squelch appropriately, keep a watch where required, and use low power when it is sufficient. Think through the station called, your identity, purpose and proposed working channel before pressing transmit.
How do distress, urgency and safety differ?
Distress concerns grave and imminent danger requiring immediate assistance. Urgency concerns an urgent message about the safety of a person or vessel without meeting the distress threshold. Safety traffic concerns important navigational or meteorological warnings. The category must fit the real situation; it is not chosen for dramatic effect.
What is the relationship between DSC and voice?
Digital Selective Calling can send a formatted alert using a vessel's radio identity and selected category. The appropriate voice procedure then carries the spoken information and coordination. Channel 70 is reserved for DSC signalling, not ordinary voice conversation; channel choice for voice traffic follows the applicable procedure and local arrangements.
- Listen and prepare before transmitting.
- Use the priority that matches the actual situation.
- Keep DSC alerting and subsequent voice traffic distinct.
Primary references used for this guide
Compass is an independent revision publisher. These maintained official, regulatory and standards-body references anchor the scope above; always check their current operational material for a real passage.
- GMDSS VHF DSC procedures for small boat users
Maritime and Coastguard Agency
- MGN 324 (M+F) Amendment 2: safe use of VHF radio and AIS
Maritime and Coastguard Agency
Check your understanding
Marine radio questions
A boat has a Ship Radio Licence and an MMSI. What separate operator condition applies to ordinary SRC-covered use?
An appropriate operator certificate, or direct supervision by someone who holds one
Read the answerA yacht is being driven onto rocks, cannot arrest the approach and needs immediate outside help. Which priority is appropriate?
Mayday, because the danger is grave and imminent and immediate assistance is required
Read the answerWhat does an MMSI identify?
An assigned maritime radio station or group identity
Read the answerWhat is an EPIRB's primary alerting function?
Send a vessel-associated 406 MHz distress alert through the satellite system
Read the answerWhat is the difference between Mayday and Pan-Pan?
Mayday is distress with grave and imminent danger; Pan-Pan is urgency without immediate grave danger.
Read the answerWhat is the difference between VHF Channel 16 and Channel 70?
Channel 16 is for voice distress, urgency, safety and calling; Channel 70 is for DSC signalling only, with no voice traffic.
Read the answerWhat may safely be concluded from an AIS display with no target at the harbour entrance?
Only that no received AIS report currently creates a displayed target
Read the answerWhat should you do before making a routine marine VHF voice call?
Listen and confirm the channel is clear of existing or higher-priority traffic
Read the answerWhich channel is used for VHF DSC digital signalling?
Channel 70
Read the answerWhich description of Channel 16 is operationally correct?
It carries distress, urgency, safety and initial calling by voice; routine traffic moves away promptly
Read the answerWhich phrase correctly introduces your own vessel identity in a routine voice call?
This is
Read the answerWhy should detailed routine traffic move from an initial calling route to a suitable working channel?
To keep the calling and safety route clear
Read the answer