Channels, Simplex, Duplex and Protected Use
Channel purpose, simplex and duplex operation, calling and working channels, and the special restrictions on channels 16 and 70.
How to prepare for the Marine Radio SRC
Build from station licensing and radio controls to disciplined voice and DSC traffic, then rehearse distress, urgency, safety, false-alert and GMDSS decisions on training equipment.
Core concepts
Concept 1
Simplex uses one frequency for both directions in turn, while duplex channel pairs support separate transmit and receive paths through a coast service.
Exam cue: Identify the service and local channel plan before transmitting.
Concept 2
Channel 16 is for distress, urgency, very brief safety traffic and initial calling before transfer to a suitable working channel.
Exam cue: Keep initial calling brief and nominate or accept a lawful working channel promptly.
Concept 3
Channel 70 carries DSC data only and must never be used for voice; port, ship-movement and other assigned channels are restricted to their designated traffic.
Exam cue: Check whether the selected working channel is suitable for inter-ship, port or coast-station use.
Risk pitfalls and guardrails
Continuing a routine conversation on channel 16 after contact is established.
Guardrail: Do not present the 601-item authoring target as an official RYA paper and do not treat static study as a substitute for the recognised written and practical examination.
Attempting a voice call on channel 70.
Guardrail: Do not present the 601-item authoring target as an official RYA paper and do not treat static study as a substitute for the recognised written and practical examination.
Using a port-operations channel for unrelated social or commercial traffic.
Guardrail: Do not present the 601-item authoring target as an official RYA paper and do not treat static study as a substitute for the recognised written and practical examination.
Memory anchors
16
Distress, urgency, brief safety and initial calling before moving off.
70
DSC data only; never radiotelephony voice.
Simplex
Both stations take turns on one frequency.
Duplex
Transmit and receive use paired frequencies, normally through a coast service.
Call Then Move
Establish contact briefly and continue on an appropriate working channel.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
What traffic is permitted on VHF channel 70?
After initial routine contact on channel 16, what should happen?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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