NIMASA GMDSS GOC Exam flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Sea Area A1

Sea area within VHF coverage of a coast station providing continuous DSC alerting, typically about 20–30 nautical miles from shore.

Sea Area A3

Sea area beyond A1 and A2 but within coverage of an Inmarsat geostationary satellite, approximately between 70°N and 70°S.

GMDSS functional elements

Distress alerting, SAR coordination, distress and safety communications, maritime safety information, and general radiocommunications.

Reserve source of energy

Dedicated battery providing emergency power to GMDSS equipment for 6 hours (cargo ships without emergency generator) or 1 hour if generator available.

Two SARTs requirement

Ships of 500 GT and above must carry two SARTs, one on each side of the bridge, plus three portable VHF radios for survival craft.

406 MHz EPIRB

Satellite distress beacon transmitting digital alert to COSPAS-SARSAT, including MMSI, position, and nature of distress; also has 121.5 MHz homing.

VHF Ch 70

DSC distress and calling frequency at 156.525 MHz; used only for DSC, no voice communication permitted.

MF DSC distress frequency

2187.5 kHz is the MF DSC distress and safety calling frequency; watchkeeping required for Sea Area A2.

Frequency to wavelength formula

Wavelength in meters equals 300 divided by frequency in MHz; for 156.8 MHz, wavelength is approximately 1.91 meters.

Ground wave propagation

MF radio waves follow Earth's curvature along the surface, giving reliable range of about 100–150 nautical miles.

DSC distress alert contents

Includes ship's MMSI, position, time, nature of distress, and communication mode (radiotelephony or telex) for follow-up.

MAYDAY signal

Spoken radiotelephony distress signal indicating a ship or person is in grave and imminent danger and requires immediate assistance.

DSC acknowledgment

Sent by coast station or ship in vicinity on the distress frequency; includes acknowledging station's MMSI and confirms receipt.

Inmarsat-C distress alert

Sent by pressing dedicated distress button, selecting nature of distress, and transmitting via satellite to a Land Earth Station.

SafetyNET

Inmarsat Enhanced Group Call service used to broadcast Maritime Safety Information to ships in areas outside NAVTEX coverage.

Inmarsat ocean regions

Four coverage areas: Atlantic Ocean Region-East, Atlantic Ocean Region-West, Indian Ocean, and Pacific Ocean, each with a satellite.

NAVTEX frequencies

518 kHz international, 490 kHz national, and 4209.5 kHz for HF; uses narrow-band direct printing for MSI delivery.

NAVTEX message types

Alphabetical codes: A navigational warnings, B meteorological, C ice, D SAR, E weather forecast, F pilot, etc.

MSI definition

Maritime Safety Information includes navigational warnings, meteorological warnings, SAR information, and other urgent safety messages.

PAN PAN signal

Urgency signal indicating a station has a very urgent message concerning safety of a ship or person but not immediate distress.

SÉCURITÉ signal

Safety signal used to announce an important navigational or meteorological warning; has lower priority than distress and urgency.

Distress message contents

Includes MAYDAY, ship's name/call sign/MMSI, position, nature of distress, assistance required, and number of persons on board.

False distress alert cancellation

Immediately transmit DSC cancellation on the distress frequency and a voice message on associated radiotelephony channel to inform all stations.

SART operating frequency

Operates in the 9 GHz (X-band) marine radar band, responding to radar interrogation with a series of dots on the radar display.

SART battery duration

Typically provides 96 hours standby and 8 hours operational; expiry date must be checked and battery replaced as required.

AIS-SART

Alternative to radar SART that transmits AIS messages, displayed on AIS equipment, showing position of survival craft.

Battery specific gravity

Measurement of electrolyte density in lead-acid batteries; indicates state of charge, typically 1.250–1.280 when fully charged.

Antenna SWR check

Standing Wave Ratio should be measured periodically; high SWR indicates antenna or cable fault, reducing transmission efficiency.

Emergency power switchover

Reserve source must automatically connect to GMDSS equipment within 30 seconds of main power failure, or manually if allowed.

GMDSS operator certificate

General Operator's Certificate (GOC) required for operators on GMDSS-equipped vessels; Restricted Operator's Certificate (ROC) for limited areas.

Radio log retention

Radio log must be kept for at least three years; records include distress, urgency, safety communications, and equipment tests.

Silence periods

Observed on 2182 kHz during the first three and last three minutes of each half-hour (00–03 and 30–33) for distress watch.