GMDSS Practice Questions

1. On which VHF channel are DSC distress alerts transmitted?

• A.Channel 70✓
• B.Channel 13
• C.Channel 22A
• D.Channel 16

Why: VHF DSC distress, urgency, safety and routine alerts are sent on Channel 70. Channel 16 remains the voice distress and calling channel.

2. GMDSS Sea Area A1 is defined as the area within range of:

• A.Inmarsat satellite coverage
• B.An HF coast station
• C.An MF coast station with DSC
• D.At least one VHF coast station with continuous DSC alerting✓

Why: Sea Area A1 lies within radiotelephone range of at least one VHF coast station providing continuous DSC alerting — roughly 20–30 nautical miles.

3. What does the 9-digit MMSI identify?

• A.The assigned NAVTEX area
• B.The vessel's documentation number
• C.The Maritime Mobile Service Identity used in DSC✓
• D.The EPIRB battery expiration

Why: The MMSI (Maritime Mobile Service Identity) is a unique 9-digit number that identifies a ship station (or coast/group station) in Digital Selective Calling.

4. If you accidentally transmit a false DSC distress alert, you must:

• A.Ignore it; the system will time out
• B.Cancel it at once by voice on Channel 16, stating it was inadvertent✓
• C.Disconnect the antenna
• D.Change your MMSI

Why: A false distress alert must be cancelled immediately — broadcast a cancellation by voice on Channel 16 (and by DSC where possible), identifying your vessel and MMSI and stating the alert was sent in error.

5. A GMDSS-connected DSC distress alert automatically includes:

• A.The vessel's MMSI and, if connected to GPS, its position and time✓
• B.The crew list
• C.The nearest port
• D.The cargo manifest

Why: A DSC distress alert automatically sends the vessel's MMSI and, when the radio is connected to a position source (GPS), the vessel's latitude/longitude and the time of the position.