Italy LRC Marine Radio cheat sheet

GMDSS has four sea areas: A1 within VHF DSC coast coverage (about 20-30 NM), A2 within MF DSC coverage (about 100-150 NM) excluding A1, A3 within Inmarsat geostationary coverage (about 70°N-70°S) excluding A1/A2, A4 the remaining polar waters.

A1 carriage: VHF DSC watch on Ch 70, VHF Ch 16 radiotelephony, DSC distress alerting, and a 406 MHz EPIRB (or 406 MHz via VHF Ch 70 from 1 February 2022 alternative allowed by SOLAS).

A2 carriage adds MF/HF DSC watch on 2187.5 kHz, MF radiotelephony on 2182 kHz, and DSC distress alerting on MF; a 406 MHz EPIRB is mandatory.

A3 carriage: Inmarsat ship earth station (or HF DSC as alternative) capable of distress alerting, plus continuous watch appropriate to the equipment fitted; 406 MHz EPIRB required.

A4 carriage: MF/HF equipment with DSC and NBDP (or Inmarsat not usable in A4), continuous HF DSC watch, and 406 MHz EPIRB.

Functional requirements: distress alerting, SAR co-ordination, on-scene communications, locating signals, maritime safety information (MSI), general radiocommunications, and bridge-to-bridge communications.

Sources of energy: main and emergency (reserve) supply; reserve must feed VHF and MF/HF (or SES) for at least 1 hour (6 hours if no emergency generator) and the emergency light.

Duplication: ships in A2/A3/A4 must carry two separate means of distress alerting, or one means plus a spare; each item must be independent of the other.

Radio log and daily/weekly/monthly tests are part of the carriage regime: daily DSC self-test, weekly transmitter test on a non-distress frequency, monthly battery and EPIRB check.

Priority order: distress (MAYDAY), urgency (PAN PAN), safety (SECURITE), then routine; DSC uses distress 112, urgency 110, safety 108, routine 100 in the 'nature of distress/signal' field.

DSC distress alert: format specifier 'distress', nature of distress, position (from GNSS), time UTC, subsequent communication mode (radiotelephony), and 'distress' in the telecommand field.

DSC distress alert is normally sent on 2187.5 kHz (MF), 8414.5 kHz (HF), or VHF Ch 70; it is repeated only if no acknowledgment is received, after a random delay of 3.5-4.5 minutes.

Distress call by radiotelephony: MAYDAY x3, THIS IS, station name/call sign/MMSI, MAYDAY, name/call sign, position, nature of distress, assistance required, number of persons on board, other information.

Distress acknowledgment by coast station: MAYDAY, name of distressed station x3, THIS IS, coast station name, RECEIVED MAYDAY, then relay instructions.

Distress relay: used when the distressed station cannot communicate; the relaying station transmits MAYDAY RELAY x3 and identifies itself, then relays the original message.

Urgency (PAN PAN): used for serious but not immediate danger, medical advice, or man overboard; sent on 2182 kHz, 4125 kHz, 6215 kHz, 8291 kHz, 12290 kHz, 16420 kHz, or VHF Ch 16.

Safety (SECURITE): navigational warnings, meteorological warnings, and MSI; announced on DSC 108 (or via SafetyNET) then broadcast by radiotelephony/NBDP on the associated working frequency.

Silence periods: 00-03 and 30-33 minutes past each hour on 2182 kHz and 500 kHz (legacy) are reserved for distress and calling; do not transmit routine traffic during these periods.

VHF Ch 16 (156.800 MHz) is the international distress, safety and calling channel; Ch 70 (156.525 MHz) is the DSC channel and must never carry voice.

Working channels: Ch 06 (intership), Ch 08, Ch 72, Ch 77 (intership), Ch 13 (bridge-to-bridge, low power 1 W), Ch 09 (marina), Ch 10, Ch 11, Ch 12, Ch 14 (port operations).

Ch 75 and Ch 76 are reserved for navigation-related intership communications; Ch 15 and Ch 17 are low-power intership channels; Ch 87B/88B are private/port channels in some regions.

DSC on Ch 70: only one transmission at a time; a DSC distress alert is followed by a voice MAYDAY on Ch 16; the DSC acknowledgment is sent by coast station or ship in the vicinity.

Dual watch: the VHF set must monitor Ch 16 and Ch 70 continuously; DSC watchkeeping on Ch 70 is mandatory for A1 vessels and is normally automatic.

Transmit power: 25 W maximum for ship VHF; use 1 W for short-range and bridge-to-bridge; range is line-of-sight, roughly 1.23 × √h (NM, h in metres) plus antenna height of the other station.

VHF channel bandwidth is 25 kHz (12.5 kHz in some regions); duplex channels use a 4.6 MHz offset between ship and coast frequencies.

Call procedure: listen on Ch 16, call 'station name x3, THIS IS, own name x3', propose a working channel, then move to the working channel for the exchange.

Radio checks use Ch 16 or a working channel with a coast station; the reply is 'received loud and clear' or a readability/signal strength report (1-5 scale).

MF distress and calling: 2182 kHz (voice), 2187.5 kHz (DSC); MF working: 2045, 2048, 2065, 2079, 2082, 2085, 2090 kHz.

HF distress and calling: 4125, 6215, 8291, 12290, 16420 kHz (voice); DSC: 4207.5, 6312, 8414.5, 12577, 16804.5 kHz; NBDP: 4177.5, 6268, 8376.5, 12520, 16695 kHz.

HF bands are divided into 4, 6, 8, 12, 16, 22, 25 MHz maritime bands; each band has a distress/calling channel, a DSC channel, an NBDP channel and working channels.

NBDP (narrow-band direct printing) uses FEC (forward error correction) for broadcast and ARQ for point-to-point; it operates on HF and is used for MSI and distress traffic.

DSC on HF requires the correct format: distress (112), all ships (116), group (114), individual (120), geographic area (102); the 'telecommand' field specifies the subsequent mode (FEC, ARQ, radiotelephony).

HF propagation depends on ionospheric layers (D, E, F1, F2); the D layer absorbs lower frequencies by day, so higher bands are used during daylight and lower bands at night.

Maximum usable frequency (MUF) is the highest frequency refracted by the ionosphere; the optimum working frequency is about 85% of MUF; LUF is the lowest usable frequency.

MF groundwave range is typically 100-150 NM by day; at night the skywave extends MF range considerably but causes fading and interference.

A ship's MF/HF installation must have a DSC watch receiver on 2187.5 kHz and the distress frequencies, with a dedicated DSC controller and printer or display.

Inmarsat provides global coverage between about 70°N and 70°S via geostationary satellites; it is the primary A3 distress alerting system.

Inmarsat services: Fleet 77/FleetBroadband for voice and data, Mini-C for MSI, and Inmarsat-C for distress alerting and two-way messaging.

Inmarsat-C distress alert is initiated by pressing the distress button (protected by a cover); it sends a priority 3 distress message to the LES/RCC with position and nature of distress.

NAVTEX broadcasts on 518 kHz (international, English), 490 kHz (national, local language) and 4209.5 kHz (tropical); range about 200-400 NM.

NAVTEX message types: A navigational warnings, B meteorological warnings, C ice reports, D SAR information, E weather forecasts, F pilot service, G AIS, H LORAN, I, J SATNAV, K other, L additional, V, W, X, Y special, Z no message.

NAVTEX receiver must be set to the correct station and message types; it prints or displays messages with a header containing station ID, message type, and serial number.

SafetyNET is Inmarsat's Enhanced Group Call (EGC) service for MSI in A3 waters; it broadcasts to fixed areas (NAVAREAs) and to groups of ships.

SafetyCAST is the Iridium-based MSI service (GMDSS recognised) providing global MSI coverage, including polar regions (A4).

NAVAREAs: METAREAs I-XVI and NAVAREAs I-XXI; Italy is in NAVAREA III (Mediterranean) and METAREA III.

MSI reception must be automatic and continuous; the receiver must be capable of receiving MSI on the appropriate frequencies or via the satellite service.

406 MHz EPIRB: transmits a digital distress message to the COSPAS-SARSAT system with the ship's identity (MMSI or beacon hex ID), position (if GNSS-equipped), and nature of distress; detected by polar-orbiting and geostationary satellites.

EPIRB registration: the beacon must be registered with the national authority (in Italy, the MMSI/beacon database) and the registration updated when the vessel changes flag, name or owner.

EPIRB activation: manual (break seal, switch to ON) or automatic (hydrostatic release when submerged); the beacon floats and transmits on 406 MHz and 121.5 MHz (homing).

EPIRB battery and test: battery life typically 48 hours at -20°C; perform a self-test monthly (not a live transmission); battery replacement interval is typically 5 years or as marked.

SART: operates in the 9 GHz (X-band) band, responds to radar interrogation with a series of 12 pulses across the radar screen, giving a line of 12 dots.

SART range is about 5-10 NM depending on radar antenna height; it must be mounted at least 1 m above sea level and switched on only when abandoning ship.

SART battery provides at least 96 hours in standby and 8 hours in operation; test using the built-in test function or a radar, not by transmitting continuously.

AIS-SART: transmits AIS messages (Message 1 and 14) on Ch 87B/88B, showing as a SAR target on AIS displays; range similar to AIS (a few NM).

EPIRB and SART are locating devices, not alerting devices; the EPIRB alerts via satellite, the SART/ AIS-SART helps on-scene SAR locate the survival craft.

The ship station licence is issued by the flag state authority; in Italy by the Ministero delle Imprese e del Made in Italy (MIMIT) - formerly MISE.

Operator certificates: GMDSS General Operator's Certificate (GOC) for A1-A4, Restricted Operator's Certificate (ROC) for A1, and Short Range Certificate (SRC) for VHF-only.

The MMSI is a 9-digit number: MID (3 digits) + ship station identity; Italy's MID is 247; group MMSI starts with 0, coast station MMSI starts with 00.

Call sign and MMSI must be programmed into DSC, AIS and EPIRB; the EPIRB hex ID is separate from the MMSI but linked in the registration database.

Distress frequencies must be used only for distress, urgency and safety; test transmissions are made on a non-distress frequency with low power or into a dummy load.

The Radio Regulations (ITU RR) and SOLAS Chapter IV govern GMDSS; the ITU RR Article 30 covers distress and safety communications.

Station identification: voice uses the ship's name and call sign; DSC uses the MMSI; NBDP uses the MMSI or call sign depending on the service.

Licence and certificates must be on board and available for inspection; the radio log must record distress, urgency and safety traffic and tests.

Frequency tolerances: MF/HF transmitter frequency error must be within 10 Hz for MF and 15 Hz for HF; VHF within 10 ppm.

Ionospheric layers: D (absorbs MF/HF by day), E (sporadic E), F1 and F2 (main refraction); F2 is highest at night and in winter.

Skywave skip distance and skip zone: the area between groundwave range and the first skywave return where no signal is received.

Antenna types: vertical whip for VHF/MF/HF, long wire for HF, and dipole; VHF antennas are vertically polarised; HF antennas need a good ground (counterpoise).

VSWR (voltage standing wave ratio) should be below 2:1; high VSWR indicates antenna or feeder fault and can damage the transmitter.

Coaxial cable loss increases with frequency; use low-loss cable (e.g., RG-213 or better) and keep runs short; PL-259/SO-239 connectors must be waterproofed.

Battery types: lead-acid (vented or VRLA) and lithium; the reserve supply must be independent of the main and capable of the required duty cycle.

Battery maintenance: check electrolyte level (vented), specific gravity (about 1.265 fully charged), terminal tightness, and charge voltage (about 13.8 V for 12 V lead-acid).

Emergency power: the reserve source must be able to supply the radio installation for the required period; test it weekly and log the result.

Basic fault-finding: no transmit - check power, fuse, antenna VSWR, PTT; no receive - check squelch, volume, antenna, and DSC controller link.

EMC: keep transmitting antennas away from receiving antennas and from the EPIRB, SART and GNSS antennas; observe manufacturer separation distances.

Common interference sources on board: radar, VHF/HF transmitters, inverters, LED lighting, battery chargers, and electric motors; use shielded cable and ferrites.

Do not transmit on VHF/HF near the EPIRB or SART during testing; a live 406 MHz transmission can trigger a false alert and SAR response.

False alerts: if an EPIRB is activated accidentally, switch it off immediately and notify the RCC and coast station; a DSC false distress alert must be cancelled by a DSC 'distress cancellation' and a voice call.

RF exposure: do not stand within the near field of a transmitting antenna; keep the antenna at least 1-2 m from personnel; HF transmissions can cause RF burns.

Battery safety: lead-acid batteries emit hydrogen - no open flames, ventilate the battery compartment; use insulated tools to avoid short circuits.

Lightning protection: antenna systems should be grounded when not in use; disconnect antennas during thunderstorms if practicable.

Operational safety: keep the radio room tidy, secure loose equipment, and ensure the DSC controller and EPIRB are accessible in an emergency.

Interference reporting: record the time, frequency, and nature of interference in the radio log and report persistent interference to the flag state authority.

GMDSS sea areas: A1 VHF DSC coverage (~20-30 NM), A2 MF DSC coverage (~100-150 NM) excluding A1, A3 Inmarsat coverage (70°N-70°S) excluding A1/A2, A4 polar waters.

A1 minimum: VHF DSC on Ch 70, VHF Ch 16 voice, DSC distress alerting, and a 406 MHz EPIRB (or approved alternative).

A2 adds MF DSC watch on 2187.5 kHz, MF voice on 2182 kHz, and MF DSC distress alerting.

A3 requires Inmarsat SES (or HF DSC alternative) for distress alerting plus continuous watch; 406 MHz EPIRB mandatory.

A4 requires MF/HF with DSC and NBDP, continuous HF DSC watch, and 406 MHz EPIRB.

Reserve energy: at least 1 hour for VHF/MF/HF (6 hours if no emergency generator), plus emergency lighting.

Two independent means of distress alerting are required in A2/A3/A4, or one means plus a spare.

DSC distress = 112, urgency = 110, safety = 108, routine = 100 in the nature-of-distress field.

DSC distress alert includes position, time UTC, nature of distress, and telecommand (e.g., radiotelephony).

DSC distress alert is repeated only if unacknowledged, after a random delay of 3.5-4.5 minutes.

Voice MAYDAY: MAYDAY x3, THIS IS, name/call sign/MMSI, MAYDAY, name/call sign, position, nature of distress, assistance required, persons on board.

Distress acknowledgment: MAYDAY, distressed station x3, THIS IS, coast station, RECEIVED MAYDAY.

Distress relay: MAYDAY RELAY x3, then relay the original message when the distressed station cannot communicate.

PAN PAN for urgency (medical, man overboard); SECURITE for safety (navigational/meteorological warnings).

Silence periods on 2182 kHz are 00-03 and 30-33 minutes past each hour.

Ch 16 (156.800 MHz) = distress, safety and calling; Ch 70 (156.525 MHz) = DSC only, never voice.

Working channels: Ch 06, 08, 72, 77 (intership); Ch 13 bridge-to-bridge at 1 W; Ch 09 marina; Ch 10-14 port operations.

Ch 75/76 reserved for navigation-related intership; Ch 15/17 low-power intership.

DSC on Ch 70 is followed by a voice MAYDAY on Ch 16; the coast station or nearby ship sends the DSC acknowledgment.

Dual watch monitors Ch 16 and Ch 70 continuously; DSC watch on Ch 70 is mandatory in A1.

Ship VHF maximum power is 25 W; use 1 W for short range and bridge-to-bridge.

VHF range is line-of-sight, approximately 1.23 × √h (NM, h in metres) plus the other station's antenna height.

Call procedure: listen on Ch 16, call 'name x3, THIS IS, own name x3', propose a working channel, then move to it.

MF distress/calling: 2182 kHz voice, 2187.5 kHz DSC; MF working: 2045, 2048, 2065, 2079, 2082, 2085, 2090 kHz.

HF voice distress: 4125, 6215, 8291, 12290, 16420 kHz; HF DSC: 4207.5, 6312, 8414.5, 12577, 16804.5 kHz.

HF NBDP distress: 4177.5, 6268, 8376.5, 12520, 16695 kHz.

NBDP uses FEC for broadcast and ARQ for point-to-point; used for MSI and distress traffic on HF.

HF propagation: D layer absorbs by day; F2 layer refracts; use higher bands by day, lower bands at night.

MUF is the highest usable frequency; optimum working frequency is about 85% of MUF; LUF is the lowest usable frequency.

MF groundwave range is typically 100-150 NM; skywave at night extends range but causes fading.

MF/HF installation requires DSC watch on 2187.5 kHz and a dedicated DSC controller with printer or display.

Inmarsat covers about 70°N-70°S via geostationary satellites; it is the primary A3 distress alerting system.

Inmarsat-C distress alert is sent by pressing the protected distress button; it goes to the LES/RCC with position and nature of distress.

NAVTEX frequencies: 518 kHz international (English), 490 kHz national, 4209.5 kHz tropical; range about 200-400 NM.

NAVTEX message types: A navigational, B meteorological, C ice, D SAR, E weather forecast, F pilot, G AIS, H LORAN, J SATNAV, K other, Z no message.

SafetyNET is Inmarsat EGC for MSI in A3, broadcast to NAVAREAs and groups of ships.

SafetyCAST is the Iridium-based MSI service providing global coverage, including A4 polar regions.

Italy is in NAVAREA III and METAREA III (Mediterranean).

MSI reception must be automatic and continuous, on the appropriate frequencies or via satellite.

406 MHz EPIRB transmits identity (MMSI/hex ID), position (if GNSS) and nature of distress to COSPAS-SARSAT; also transmits on 121.5 MHz for homing.

EPIRB must be registered with the national authority and updated when flag, name or owner changes.

EPIRB activation: manual (break seal, switch ON) or automatic (hydrostatic release); the beacon floats and transmits.

EPIRB battery life is typically 48 hours at -20°C; self-test monthly, battery replacement typically every 5 years.

SART operates in the 9 GHz (X-band) band and shows as a line of 12 dots on a radar screen.

SART range is about 5-10 NM; mount at least 1 m above sea level; switch on only when abandoning ship.

SART battery: at least 96 hours standby and 8 hours operation; test with the built-in test function.

AIS-SART transmits AIS messages on Ch 87B/88B and appears as a SAR target on AIS displays.

EPIRB alerts via satellite; SART/AIS-SART helps on-scene SAR locate the survival craft.

Ship station licence is issued by the flag state; in Italy by MIMIT (formerly MISE).

Operator certificates: GOC for A1-A4, ROC for A1, SRC for VHF-only.

MMSI is 9 digits: MID (Italy = 247) + ship station identity; group MMSI starts with 0; coast station MMSI starts with 00.

Call sign and MMSI must be programmed into DSC, AIS and EPIRB; the EPIRB hex ID is separate but linked in the registration database.

Distress frequencies are reserved for distress, urgency and safety; tests use non-distress frequencies or a dummy load.

GMDSS is governed by SOLAS Chapter IV and the ITU Radio Regulations; Article 30 covers distress and safety communications.

Voice identification uses ship's name and call sign; DSC uses the MMSI; NBDP uses MMSI or call sign.

Licence and certificates must be on board; the radio log records distress, urgency, safety traffic and tests.

Frequency tolerance: within 10 Hz for MF and 15 Hz for HF; VHF within 10 ppm.

Ionospheric layers: D absorbs MF/HF by day; E sporadic E; F1 and F2 refract; F2 is highest at night and in winter.

Skip zone: the area between groundwave range and the first skywave return where no signal is received.

Antennas: vertical whip for VHF/MF/HF, long wire for HF, dipole; VHF is vertically polarised; HF needs a good ground or counterpoise.

VSWR should be below 2:1; high VSWR indicates antenna or feeder fault and can damage the transmitter.

Coaxial loss increases with frequency; use low-loss cable, keep runs short, and waterproof PL-259/SO-239 connectors.

Reserve battery must be independent of the main supply and capable of the required duty cycle.

Battery checks: electrolyte level, specific gravity (~1.265 fully charged), terminal tightness, charge voltage (~13.8 V for 12 V lead-acid).

Fault-finding: no transmit - check power, fuse, VSWR, PTT; no receive - check squelch, volume, antenna, DSC controller link.

Keep transmitting antennas away from receiving antennas, EPIRB, SART and GNSS antennas; observe manufacturer separation distances.

Interference sources on board: radar, VHF/HF transmitters, inverters, LED lighting, battery chargers, electric motors; use shielded cable and ferrites.

Do not transmit near the EPIRB or SART during testing; a live 406 MHz transmission can trigger a false alert and SAR response.

If an EPIRB is activated accidentally, switch it off immediately and notify the RCC and coast station.

A DSC false distress alert must be cancelled by a DSC distress cancellation and a voice call.

RF exposure: do not stand within the near field of a transmitting antenna; keep 1-2 m from HF antennas to avoid RF burns.

Lead-acid batteries emit hydrogen: no open flames, ventilate the battery compartment, use insulated tools.

Ground antenna systems when not in use and disconnect during thunderstorms where practicable.

Record time, frequency and nature of interference in the radio log and report persistent interference to the flag state authority.

Sea area A1: within VHF DSC coast station coverage, about 20-30 NM; A2: within MF DSC coverage, about 100-150 NM, excluding A1.

Sea area A3: within Inmarsat geostationary coverage, about 70°N-70°S, excluding A1 and A2; A4: the remaining polar waters.

A1 carriage: VHF DSC on Ch 70, VHF Ch 16 voice, DSC distress alerting, and a 406 MHz EPIRB (or approved alternative).

A2 adds MF DSC watch on 2187.5 kHz, MF voice on 2182 kHz, and MF DSC distress alerting.

A3 requires Inmarsat SES (or HF DSC alternative) for distress alerting plus continuous watch; 406 MHz EPIRB mandatory.

A4 requires MF/HF with DSC and NBDP, continuous HF DSC watch, and 406 MHz EPIRB.

Reserve energy: at least 1 hour for VHF/MF/HF (6 hours if no emergency generator), plus emergency lighting.

Two independent means of distress alerting are required in A2/A3/A4, or one means plus a spare.

Functional requirements include distress alerting, SAR co-ordination, on-scene communications, locating, MSI, general radiocommunications and bridge-to-bridge.

DSC distress = 112, urgency = 110, safety = 108, routine = 100 in the nature-of-distress field.

DSC distress alert includes position, time UTC, nature of distress, and telecommand (e.g., radiotelephony).

DSC distress alert is repeated only if unacknowledged, after a random delay of 3.5-4.5 minutes.

Voice MAYDAY: MAYDAY x3, THIS IS, name/call sign/MMSI, MAYDAY, name/call sign, position, nature of distress, assistance required, persons on board.

Distress acknowledgment: MAYDAY, distressed station x3, THIS IS, coast station, RECEIVED MAYDAY.

Distress relay: MAYDAY RELAY x3, then relay the original message when the distressed station cannot communicate.

PAN PAN for urgency (medical, man overboard); SECURITE for safety (navigational/meteorological warnings).

Silence periods on 2182 kHz are 00-03 and 30-33 minutes past each hour.

DSC distress alerts are sent on 2187.5 kHz (MF), 8414.5 kHz (HF) or VHF Ch 70.

Ch 16 (156.800 MHz) = distress, safety and calling; Ch 70 (156.525 MHz) = DSC only, never voice.

Working channels: Ch 06, 08, 72, 77 (intership); Ch 13 bridge-to-bridge at 1 W; Ch 09 marina; Ch 10-14 port operations.

Ch 75/76 reserved for navigation-related intership; Ch 15/17 low-power intership.

DSC on Ch 70 is followed by a voice MAYDAY on Ch 16; the coast station or nearby ship sends the DSC acknowledgment.

Dual watch monitors Ch 16 and Ch 70 continuously; DSC watch on Ch 70 is mandatory in A1.

Ship VHF maximum power is 25 W; use 1 W for short range and bridge-to-bridge.

VHF range is line-of-sight, approximately 1.23 × √h (NM, h in metres) plus the other station's antenna height.

Call procedure: listen on Ch 16, call 'name x3, THIS IS, own name x3', propose a working channel, then move to it.

Radio checks use Ch 16 or a working channel with a coast station; reply 'received loud and clear' or a readability/signal strength report (1-5).

MF distress/calling: 2182 kHz voice, 2187.5 kHz DSC; MF working: 2045, 2048, 2065, 2079, 2082, 2085, 2090 kHz.

HF voice distress: 4125, 6215, 8291, 12290, 16420 kHz; HF DSC: 4207.5, 6312, 8414.5, 12577, 16804.5 kHz.

HF NBDP distress: 4177.5, 6268, 8376.5, 12520, 16695 kHz.

NBDP uses FEC for broadcast and ARQ for point-to-point; used for MSI and distress traffic on HF.

HF propagation: D layer absorbs by day; F2 layer refracts; use higher bands by day, lower bands at night.

MUF is the highest usable frequency; optimum working frequency is about 85% of MUF; LUF is the lowest usable frequency.

MF groundwave range is typically 100-150 NM; skywave at night extends range but causes fading.

MF/HF installation requires DSC watch on 2187.5 kHz and a dedicated DSC controller with printer or display.

DSC format specifiers: distress 112, all ships 116, group 114, individual 120, geographic area 102.

Inmarsat covers about 70°N-70°S via geostationary satellites; it is the primary A3 distress alerting system.

Inmarsat-C distress alert is sent by pressing the protected distress button; it goes to the LES/RCC with position and nature of distress.

NAVTEX frequencies: 518 kHz international (English), 490 kHz national, 4209.5 kHz tropical; range about 200-400 NM.

NAVTEX message types: A navigational, B meteorological, C ice, D SAR, E weather forecast, F pilot, G AIS, H LORAN, J SATNAV, K other, Z no message.

SafetyNET is Inmarsat EGC for MSI in A3, broadcast to NAVAREAs and groups of ships.

SafetyCAST is the Iridium-based MSI service providing global coverage, including A4 polar regions.

Italy is in NAVAREA III and METAREA III (Mediterranean).

MSI reception must be automatic and continuous, on the appropriate frequencies or via satellite.

Inmarsat services include Fleet 77/FleetBroadband for voice and data, Mini-C for MSI, and Inmarsat-C for distress alerting and messaging.

406 MHz EPIRB transmits identity (MMSI/hex ID), position (if GNSS) and nature of distress to COSPAS-SARSAT; also transmits on 121.5 MHz for homing.

EPIRB must be registered with the national authority and updated when flag, name or owner changes.

EPIRB activation: manual (break seal, switch ON) or automatic (hydrostatic release); the beacon floats and transmits.

EPIRB battery life is typically 48 hours at -20°C; self-test monthly, battery replacement typically every 5 years.

SART operates in the 9 GHz (X-band) band and shows as a line of 12 dots on a radar screen.

SART range is about 5-10 NM; mount at least 1 m above sea level; switch on only when abandoning ship.

SART battery: at least 96 hours standby and 8 hours operation; test with the built-in test function.

AIS-SART transmits AIS messages on Ch 87B/88B and appears as a SAR target on AIS displays.

EPIRB alerts via satellite; SART/AIS-SART helps on-scene SAR locate the survival craft.

Ship station licence is issued by the flag state; in Italy by MIMIT (formerly MISE).

Operator certificates: GOC for A1-A4, ROC for A1, SRC for VHF-only.

MMSI is 9 digits: MID (Italy = 247) + ship station identity; group MMSI starts with 0; coast station MMSI starts with 00.

Call sign and MMSI must be programmed into DSC, AIS and EPIRB; the EPIRB hex ID is separate but linked in the registration database.

Distress frequencies are reserved for distress, urgency and safety; tests use non-distress frequencies or a dummy load.

GMDSS is governed by SOLAS Chapter IV and the ITU Radio Regulations; Article 30 covers distress and safety communications.

Voice identification uses ship's name and call sign; DSC uses the MMSI; NBDP uses MMSI or call sign.

Licence and certificates must be on board; the radio log records distress, urgency, safety traffic and tests.

Frequency tolerance: within 10 Hz for MF and 15 Hz for HF; VHF within 10 ppm.

Ionospheric layers: D absorbs MF/HF by day; E sporadic E; F1 and F2 refract; F2 is highest at night and in winter.

Skip zone: the area between groundwave range and the first skywave return where no signal is received.

Antennas: vertical whip for VHF/MF/HF, long wire for HF, dipole; VHF is vertically polarised; HF needs a good ground or counterpoise.

VSWR should be below 2:1; high VSWR indicates antenna or feeder fault and can damage the transmitter.

Coaxial loss increases with frequency; use low-loss cable, keep runs short, and waterproof PL-259/SO-239 connectors.

Reserve battery must be independent of the main supply and capable of the required duty cycle.

Battery checks: electrolyte level, specific gravity (~1.265 fully charged), terminal tightness, charge voltage (~13.8 V for 12 V lead-acid).

Fault-finding: no transmit - check power, fuse, VSWR, PTT; no receive - check squelch, volume, antenna, DSC controller link.

Emergency power test: run the reserve supply weekly and log the result in the radio log.

Keep transmitting antennas away from receiving antennas, EPIRB, SART and GNSS antennas; observe manufacturer separation distances.

Interference sources on board: radar, VHF/HF transmitters, inverters, LED lighting, battery chargers, electric motors; use shielded cable and ferrites.

Do not transmit near the EPIRB or SART during testing; a live 406 MHz transmission can trigger a false alert and SAR response.

If an EPIRB is activated accidentally, switch it off immediately and notify the RCC and coast station.

A DSC false distress alert must be cancelled by a DSC distress cancellation and a voice call.

RF exposure: do not stand within the near field of a transmitting antenna; keep 1-2 m from HF antennas to avoid RF burns.

Lead-acid batteries emit hydrogen: no open flames, ventilate the battery compartment, use insulated tools.

Ground antenna systems when not in use and disconnect during thunderstorms where practicable.

Record time, frequency and nature of interference in the radio log and report persistent interference to the flag state authority.