GMDSS & DSC Alerting Principles
Not publishedof exam
A1A2A3A4
VHF Channel Plan & Operations
Not publishedof exam
16: 156.800 MHz70: 156.525 MHz613
Distress, Urgency & Safety Procedures
Not publishedof exam
MAYDAYMAYDAY RELAYPAN-PANSÉCURITÉ
UK Regulations & Ofcom Licensing
Not publishedof exam
RYA SRCExam administrationMinimum exam ageAccepted eligibility
Phonetics, Numbers & Prowords
Not publishedof exam
ALFA and JULIETTOVEROUTROGER
Quick Facts
- Qualification
- RYA Marine Radio SRC
- Authority
- RYA on behalf of MCA
- Assessment
- Written theory and practical
- Exam age
- 16+
- 2026 exam fee
- £76; other provider charges separate
- Official weights
- Not published
- Voice distress
- Channel 16
- Digital signaling
- Channel 70 only
Radar SART and AIS-SART
Radar SART
- Responds to X-band radar
- Characteristic series of 12 marks
AIS-SART
- Transmits identity and position on AIS
- 96-hour operating performance standard
Locating devices; different receiving equipment
GMDSS and DSC Essentials
- A1
- VHF coast continuous-DSC coverage
- A2
- MF coast coverage outside A1
- A3
- Recognized satellite service supported aboard
- A4
- Outside A1, A2 and A3
- DSC purpose
- Digital alerting; voice adds situation details
- Ship MMSI
- Nine digits; ordinary ship starts MID
- Group MMSI
- 0 + MID + five digits
- Coast MMSI
- 00 + MID + four digits
Ordinary Station MMSI Pattern
Ship MID; group 0-MID; coast 00-MID; nine digits total
Other device identities also existUse the assigned identityCheck all digits before programming
Simplex and Two-Frequency Duplex
Simplex
- Same transmit and receive frequency
- Suitable for permitted direct inter-ship traffic
Duplex
- Ship and coast frequencies differ
- Ships normally cannot hear each other
Select for communication type and allocation
Choose an Appropriate Channel
- DSC digital call or alert→Channel 70 via equipment controls(No voice transmission)
- VHF voice distress→Channel 16(Maintain listening watch)
- Permitted direct inter-ship exchange→Suitable authorized simplex working channel(Check local allocation)
- Calling marina publishing Channel 80→Channel 80(Choose effective permitted power)
- Club publishes authorized M1 or M2→Use its stated UK channel(Not blanket authorization abroad)
Channels: Check Local Allocations
- 16: 156.800 MHz
- Voice distress, urgency and initial calling
- 70: 156.525 MHz
- DSC digital signaling; never voice
- 6
- Designated inter-ship safety and SAR
- 13
- Navigation-safety communication
- 67 in UK
- Coastguard safety communication as directed
- 72 and 77
- Permitted inter-ship working channels
- 80 ship/coast pair
- 157.025 MHz / 161.625 MHz
- UK M1 / M2
- 157.850 MHz / 161.425 MHz
Routine Communication and Position
- Routine call accepted by another ship→Use agreed permitted simplex channel(Avoid occupied channels)
- Coast station assigns working channel→Confirm and use that channel(Follow station’s traffic instructions)
- Giving latitude and longitude→State digits, minutes and hemispheres(Check current position and time)
- Giving bearing and distance→State true bearing FROM named reference(Include distance and units)
Radio Controls and Reliable Contact
- Power selection
- Lowest effective power; obey channel limits
- Squelch
- Just above noise; preserve weak signals
- Volume
- Audible without unnecessary distortion
- Dual watch
- Priority and working-channel monitoring
- Simplex
- Same transmit and receive frequency
- Duplex
- Paired ship and coast frequencies
- Antenna height
- Improves radio horizon; no guaranteed range
- GNSS input
- Verify position, time and connection
MIPDANIO: Voice Distress Message
Mayday, Identity, Position, Distress, Assistance, Number, Information, Over
Give vessel identity clearlyState position and required assistanceInclude people aboard and useful details
Distress Silence and Its End
SEELONCE MAYDAY
- Casualty or controlling station imposes silence
- Other stations must avoid interference
SEELONCE FEENEE
- Controlling station ends distress traffic
- Message identifies casualty and time
Silence alone does not end distress
Choose the Communication Priority
- Grave imminent danger requires immediate help→MAYDAY; DSC alert if available(Follow with voice on Channel 16)
- Another casualty cannot transmit distress→Relay to appropriate coast station(Give known facts; avoid invented details)
- Urgent safety concern below distress threshold→PAN-PAN(Escalate if danger becomes grave)
- Important navigation or weather safety information→SÉCURITÉ(Normally move detailed message to working-channel)
- Ordinary permitted operational exchange→Routine call and working channel(Listen before transmitting)
Emergency Voice and Silence
- MAYDAY
- Grave imminent danger; immediate assistance
- MAYDAY RELAY
- Relay another station’s distress information
- PAN-PAN
- Urgent safety message below distress threshold
- SÉCURITÉ
- Navigation or meteorological safety information
- SEELONCE MAYDAY
- Casualty or controlling station imposes silence
- Distress silence
- Other stations avoid interfering with distress
- SEELONCE FEENEE
- Controlling station ends distress silence
- False alert cancellation
- Reset; self-cancel if available; voice cancellation
Priority Order
Distress, urgency, safety, routine; choose from actual danger
MAYDAY requires grave imminent dangerPAN-PAN covers urgent safetySÉCURITÉ carries safety information
False Alert and Received Distress
- Accidental DSC distress transmitted→Reset according to equipment instructions(Power-cycle may form prescribed reset)
- Radio supports distress self-cancel→Complete self-cancel procedure(Then voice cancellation remains necessary)
- False alert reset or self-cancel complete→Cancel by voice on Channel 16(Identity, MMSI and alert time)
- Another vessel’s DSC distress received→Record details; listen on Channel 16(Normally leave DSC acknowledgment to coast)
Operator Certificate and Equipment Licence
RYA SRC
- Certifies personal radio competence
- Written and practical assessment
Ofcom licence
- Authorizes specified radio equipment
- Keep licence details accurate
One does not replace the other
UK Certification and Licensing
- RYA SRC
- Personal radio operator competence certificate
- Exam administration
- RYA on behalf of MCA
- Minimum exam age
- 16 years
- Accepted eligibility
- SRC course or specified existing certificate
- 2026 RYA exam fee
- £76; course and hosting costs separate
- Ofcom Ship Radio Licence
- Named vessel’s authorized radio installation
- Ship Portable Radio Licence
- Portable equipment; territorial conditions apply
- ATIS
- Inland-waterway identification; not UK operation
Ship and Portable Radio Licences
Ship Radio Licence
- Linked to named vessel
- Licence conditions and foreign rules apply
Ship Portable Radio Licence
- Equipment not tied to one vessel
- Territorial limits; no international call sign
Portable licence is not worldwide permission
Watchkeeping and Equipment Care
- Radio watch
- Follow applicable licence and operating requirements
- Equipment test
- Approved test function; never distress alert
- Battery care
- Manufacturer schedule and expiry requirements
- EPIRB registration
- Maintain correct beacon and contact details
- NAVTEX selection
- Keep mandatory safety subjects enabled
- Passage information
- Keep shore contacts and details current
- Public correspondence AAIC
- Identifies accounting authority for communication charges
Conversation Endings and Acknowledgments
OVER / ROGER
- OVER expects a reply
- ROGER confirms receipt
OUT / WILCO
- OUT ends the exchange
- WILCO confirms intention to comply
Read back critical details when required
Clear Voice Procedure
- ALFA and JULIETT
- Standard phonetic spellings
- OVER
- Reply expected
- OUT
- Exchange finished; no reply expected
- ROGER
- Message received satisfactorily
- WILCO
- Understood and will comply
- SAY AGAIN
- Request repetition of unclear information
- Position report
- Coordinates or bearing/distance FROM reference
- Readability
- Intelligibility, not signal loudness alone
Common Traps
Treating Reset as Cancellation
Reset stops further accidental transmission ≠ Voice cancellation still required
Equipment-Specific Reset versus Blanket Power-Cycle Ban
Prescribed reset; restore operation and listening ≠ Assuming power-cycling is always prohibited
Channel 80 versus Direct Inter-Ship Traffic
Channel 80: paired ship/coast frequencies ≠ Direct inter-ship: suitable authorized simplex channel
Absolute Channel 16 Safety Ban
MCA permits very brief safety traffic ≠ Move lengthy safety messages off 16
Squelch Setting versus Weak-Signal Loss
Threshold just above background noise ≠ Overtight threshold suppressing weak signals
EPIRB Lanyard versus Defeated Float-Free Release
Manufacturer-specified lanyard attachment and deployment ≠ Tethering that defeats float-free release
Last Minute
- 1.Distress-button timing follows equipment instructions
- 2.DSC alert needs voice situation details
- 3.False alert: reset, self-cancel, voice cancellation
- 4.Coast normally sends DSC distress acknowledgment
- 5.Controller may use SEELONCE MAYDAY
- 6.Channel 70 is digital only
- 7.Channel 80 pair: 157.025/161.625 MHz
- 8.Use lowest effective permitted power
- 9.A1 is coverage, not fixed mileage
- 10.A3 depends on supported satellite service
- 11.Check beacon registration and expiry dates
- 12.Never combine OVER with OUT