FCC GMDSS flashcards

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

MAYDAY

Spoken distress signal indicating a grave and imminent danger requiring immediate assistance. Transmitted three times, followed by vessel identity, position, nature of distress, and assistance required.

PAN PAN

Urgency signal used when a vessel or person is in difficulty but not in immediate grave danger, such as serious illness or a disabled vessel not at immediate risk.

SECURITE

Safety signal used to announce navigational or meteorological warnings, or other important safety information. Transmitted three times before the safety message.

MAYDAY RELAY

Distress relay transmitted by a station not itself in distress, used when the original station cannot transmit or when a coast station or ship relays the distress message.

Silence period MF

On 2182 kHz, silence periods occur at 00 and 30 minutes past each hour, during which only distress, urgency and safety traffic may be transmitted.

Distress acknowledgement

A station hearing a distress alert acknowledges only if it can assist or if no other station has acknowledged; coast stations normally handle acknowledgement.

Sea Area A1

Sea area within VHF coverage of at least one coast station with continuous DSC alerting, approximately 20 to 30 nautical miles from the coast.

Sea Area A2

Sea area beyond A1 but within MF coverage of at least one coast station with continuous DSC alerting, approximately 100 to 150 nautical miles offshore.

Sea Area A3

Sea area beyond A1 and A2 within coverage of an Inmarsat geostationary satellite with continuous alerting, approximately between 70 degrees north and 70 degrees south.

Sea Area A4

Remaining sea areas outside A1, A2 and A3, including polar regions, requiring HF DSC and HF radiotelephony for distress alerting.

EPIRB frequencies

406 MHz COSPAS-SARSAT distress beacon transmitting to satellites; 121.5 MHz is a homing frequency used by SAR aircraft to locate the beacon.

SART operation

9 GHz radar transponder that responds to interrogating radar with a series of dots on the rescuing vessel's display, aiding location of a survival craft.

GMDSS functional requirements

Distress alerting, alert reception, distress communications, SAR coordinating communications, on-scene communications, locating signals, MSI reception, and bridge-to-bridge communications.

DSC distress frequencies

VHF Ch 70, MF 2187.5 kHz, and HF 4207.5, 6312, 8414.5, 12577 and 16804.5 kHz are the dedicated DSC distress and safety calling frequencies.

DSC distress alert content

Includes vessel MMSI, nature of distress, position, time, and communication mode. Sent by pressing the dedicated distress button, usually followed by a voice distress message.

VHF Channel 70

DSC-only channel at 156.525 MHz. Voice communications are not permitted on Ch 70; after the DSC exchange, stations move to Ch 16 or a working channel.

DSC routine call

Select the called station's MMSI and a working channel, transmit the DSC call, receive acknowledgement, then both stations switch to the working channel for voice.

MMSI structure

Nine-digit Maritime Mobile Service Identity. Ship stations have a leading digit identifying the country; coast stations begin with 00 and group stations begin with 0.

DSC distress retransmission

A distress alert is not retransmitted once acknowledged. If unacknowledged after a reasonable interval, the station may retransmit or escalate to a voice MAYDAY.

Inmarsat coverage

Geostationary satellite coverage between approximately 70 degrees north and 70 degrees south, supporting Sea Area A3 but not polar Sea Area A4.

Inmarsat-C terminal

Store-and-forward messaging terminal used for distress alerting via a protected distress button and for receiving Enhanced Group Call SafetyNET messages.

SafetyNET

Inmarsat Enhanced Group Call service that broadcasts maritime safety information, including navigational and meteorological warnings and SAR messages, to defined sea areas.

NAVTEX frequencies

518 kHz is the international English frequency; 490 kHz is used nationally; 4209.5 kHz serves tropical and coastal areas. Broadcasts typically follow a 10-minute schedule.

NAVTEX message types

Letter codes identify content: A navigational warning, B meteorological warning, C ice report, D SAR information, E forecast, F pilot service, and Z no message.

EGC receiver setup

The Enhanced Group Call receiver must be logged in to the correct ocean region and configured for the appropriate sea area to receive SafetyNET messages.

VHF Channel 16

156.800 MHz, the radiotelephony distress, safety and calling channel. Initial voice contact is made here, then traffic moves to a working channel.

NBDP distress frequencies

2174.5 kHz for MF and 4177.5, 6268, 8376.5, 12520 and 16695 kHz for HF are the narrow-band direct printing distress and safety frequencies.

ARQ versus FEC

ARQ is a two-way error-correcting mode between two stations; FEC is a one-way broadcast mode used for messages sent to multiple stations, such as navigational warnings.

ROGER and WILCO

ROGER means the message was received correctly; WILCO means the message was received and will be complied with. Both are standard radiotelephony procedure words.

FCC Part 80

The FCC rules governing maritime radio services, including ship station licensing, operator requirements, frequency use, and incorporation of ITU Radio Regulations.

GMDSS operator license

FCC license required to operate GMDSS equipment; the GMDSS Radio Operator's License does not require Morse code proficiency.

MMSI versus call sign

The MMSI is a nine-digit identity programmed into DSC and AIS equipment; the call sign is the station's radio identifier. They are distinct and both appear on the license.