FCC GMDSS Maintainer flashcards

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

GMDSS sea area A1

An area within radiotelephone coverage of at least one VHF coast station in which continuous DSC alerting is available, nominally about 20-30 nautical miles from the coast.

GMDSS sea area A3

An area outside A1 and A2 but within coverage of an Inmarsat geostationary satellite, approximately between 70 degrees north and 70 degrees south, where continuous alerting is available.

Functional requirement SOLAS IV

Ships must be able to transmit ship-to-shore distress alerts by at least two independent means using different radiocommunication services, rather than carrying specific named equipment.

MAYDAY distress message

The spoken distress signal MAYDAY sent three times, followed by THIS IS, ship identity, position, nature of distress, assistance required, persons on board and any other useful information.

PAN PAN urgency signal

The spoken signal PAN PAN sent three times, indicating an urgent message concerning the safety of a ship or person but not a distress situation requiring immediate assistance.

MAYDAY RELAY

The signal used by a station not itself in distress to relay a distress message, or by a coast station acknowledging a distress alert on behalf of a ship.

VHF Channel 70

The frequency 156.525 MHz reserved exclusively for digital selective calling; voice transmission on this channel is prohibited, and it must be continuously watched.

DSC distress alert content

A DSC distress alert contains the format specifier, the ship's MMSI, the nature of distress, the position and time from the associated GNSS, and a check sum.

MMSI structure

A nine-digit Maritime Mobile Service Identity beginning with the Maritime Identification Digits of the flag state, followed by a unique ship station number.

DSC distress retransmission

If no acknowledgment is received within about 3.5 to 4.5 minutes, the distress alert may be retransmitted, normally on the same or an alternative distress frequency.

NBDP ARQ mode

A two-way narrow-band direct-printing mode using automatic repeat request, in which the receiving station requests retransmission of errored characters, used for point-to-point telex.

NBDP FEC mode

A one-way narrow-band direct-printing mode using forward error correction, transmitting each character twice, used for broadcasts such as maritime safety information.

SSB J3E emission

Single-sideband suppressed-carrier telephony used on MF and HF distress and calling frequencies, with a 2.8 kHz bandwidth and no carrier transmitted.

Inmarsat-C distress alerting

A store-and-forward satellite service providing GMDSS distress alerting, two-way messaging and Enhanced Group Call reception for SafetyNET in sea area A3.

SafetyNET service

An Enhanced Group Call service carried over Inmarsat satellites that broadcasts maritime safety information to ships in sea area A3 and to selected areas.

Inmarsat coverage limit

Geostationary satellites provide coverage between approximately 70 degrees north and 70 degrees south, so polar regions in sea area A4 are outside Inmarsat coverage.

406 MHz EPIRB

A satellite emergency position-indicating radio beacon transmitting a digital distress message to the COSPAS-SARSAT system, including identity and, if equipped, GNSS position.

Hydrostatic release unit

A device that releases a float-free EPIRB at a depth of about 1.5 to 4 metres, allowing the beacon to float to the surface and transmit automatically.

SART radar response

A search and rescue radar transponder operating in the 9 GHz band that replies to radar interrogation with a series of twelve dots on the radar display, showing range and bearing.

EPIRB homing frequency

The 121.5 MHz transmission included in many 406 MHz EPIRBs, used by search and rescue aircraft to home in on the beacon during a rescue.

NAVTEX frequency 518 kHz

The international maritime safety information frequency used for narrow-band direct-printing broadcasts with forward error correction at 100 baud and a 170 Hz shift.

NAVTEX message types

Single-letter codes identifying content: A navigational warnings, B meteorological warnings, C ice reports, D search and rescue information, E forecasts, F pilot service messages.

MSI definition

Maritime Safety Information, comprising navigational warnings, meteorological warnings and forecasts, search and rescue information and other urgent safety information broadcast to ships.

Reserve source of energy

A battery independent of the main ship's power, required to operate the GMDSS radio installation for a specified period when the main and emergency power supplies fail.

VSWR measurement

The ratio of reflected to forward power in an antenna system; a value below about 2:1 is acceptable, and higher values indicate a fault that can damage the transmitter.

Antenna tuning unit

A matching network in MF and HF installations that transforms the antenna impedance to the value required by the transmitter for each operating frequency.

Lead-acid battery check

Verification of electrolyte specific gravity, terminal condition and charging voltage; low specific gravity indicates discharge, and sulfation reduces capacity permanently.

DSC test call

A routine call using the test category addressed to a specific coast station, confirming that the DSC controller, transmitter and antenna system are functioning correctly.

EPIRB self-test

A built-in check of the beacon's electronics, battery and, on some models, GNSS receiver, performed without transmitting a live distress alert to the satellite system.

Systematic fault-finding

A sequence of checks starting with power supply, then antenna and VSWR, then cables and connectors, then the equipment itself, using built-in test functions.

Radio log requirement

A record of tests, faults, repairs and distress communications kept on board, used to demonstrate compliance with SOLAS IV/15 during surveys.

SART battery life

Typically about 96 hours in standby and 8 hours of continuous operation; the battery expiry date must be checked and the unit tested with its built-in test function.