WPC GMDSS ROC (India) common mistakes

Candidates memorise the four definitions loosely as 'coastal, medium, satellite, polar' and then try to map a ship type onto them. The exam instead tests coverage: A1 = within VHF DSC coast station range (≈20–30 nm), A2 = within MF DSC range (≈100–150 nm) excluding A1, A3 = within Inmarsat coverage excluding A1/A2 (roughly 70°N–70°S), A4 = outside all of these. Because the definitions are cumulative and exclusive, a single misapplied boundary flips every carriage-requirement question that follows.

Voice Mayday is drilled far more often than DSC alerting, so under exam pressure candidates default to the familiar spoken format. Many also do not distinguish the two stages of a DSC distress transaction: the alert itself (a data message with MMSI, position, time and nature of distress, sent on Ch 70 or 2187.5/8414.5 kHz) and the subsequent distress traffic (voice Mayday on Ch 16 or 2182 kHz / the HF distress traffic frequency).

The 'do not acknowledge' rule for DSC distress alerts is learned as a blanket prohibition, so candidates never learn the exceptions: a ship may acknowledge after a delay (typically about 5 minutes on HF, and where no coast station has responded) and must relay a distress alert when the source cannot communicate, when a station in distress is known to be unable to transmit, or when a distress alert is received on HF from a station out of range of a coast station. The prohibition applies to routine acknowledgement, not to the duty to relay.

The numbers look interchangeable (70, 16, 2182, 2187.5, 8414.5, 4207.5, 6312, 12577, 16804.5) and candidates memorise them as a list without attaching a service to each. The exam deliberately mixes VHF and MF/HF, DSC and radiotelephony, distress and routine, to see whether the candidate holds a structured map rather than a bag of numbers.

Candidates learn 'MMSI is nine digits' and stop there. The exam tests the prefix conventions: ship stations begin with the MID (three digits identifying the flag state), group of ships use a leading 0, coast stations use a leading 00, SAR aircraft use 111, and AIS-SARTs, EPIRBs and handheld VHF DSC each have their own conventions (for example 970/972/974 for AIS-SART, EPIRB and MOB devices). Getting this wrong also corrupts answers on DSC calling and on EPIRB registration.

Both devices are small, rarely used, and described in marketing language ('satellite EPIRB', 'radar SART'), so candidates blur their functions. They also miss the practical handling points the exam likes: a 406 MHz EPIRB alerts the COSPAS-SARSAT system via satellite and provides a 121.5 MHz homing signal for aircraft and rescue craft; a SART (9 GHz) responds to a ship's or aircraft's radar with a line of dots on the display and does not communicate with satellites; an AIS-SART instead transmits AIS position reports. Handling errors (switching off too early, not registering the beacon, testing on the wrong setting) are examinable behaviours.

Both are MSI broadcast systems and both appear in the same chapter of most textbooks, so candidates merge them. The exam tests the distinctions: NAVTEX is a terrestrial MF system on 518 kHz (international, English) with 490 kHz and 4209.5 kHz for national traffic, coverage limited to roughly 200–400 nm from a coast station, using a station/time-slot schedule and message-type selection; SafetyNET is an Inmarsat Enhanced Group Call service delivering MSI to Inmarsat-covered waters (A3, and A4 is not covered by Inmarsat), addressed by circular or fixed-area calls. Reception obligations and the meaning of the NAVTEX message-type codes are also examinable.

The visible, audible watch on Ch 16 dominates training, while the silent DSC watch and the HF watch are abstract. Candidates also carry over old rules (the continuous 2182 kHz radiotelephone watch was discontinued; GMDSS watchkeeping is DSC-based with radiotelephony watch on the appropriate distress frequency) and are unsure who may keep watch. The exam tests the combination of watches required for the sea area and the qualification of the person keeping them.

Log and false-alert questions look administrative, so candidates skim them. The exam tests concrete obligations: a false distress alert must be cancelled immediately by DSC (or by voice if DSC cancellation is not possible), the station must inform the appropriate authority (coast station or RCC) and, where required, the flag administration; the event, the time, the frequencies used and the cancellation must be recorded in the radio log; the log itself is a continuous record of distress, urgency and safety traffic, watch periods, tests, position reports where required, and equipment faults, kept on board for the prescribed period.

These are the least-drilled topics on the syllabus and candidates fall back on everyday assumptions. The exam tests specific requirements: a dedicated reserve source of energy (typically a battery) capable of supplying the GMDSS installation for a defined period (commonly 1 hour for a ship with emergency generator, 6 hours for one without, with additional capacity for A2/A3/A4 as applicable), independent of the main and emergency switchboards, with charging arrangements and alarms for low voltage/failure, and with the ability to supply the distress and safety functions first. Fault-finding questions test structured diagnosis: check power, then the antenna and feeder (standing wave, water ingress, connector corrosion), then the set, then the DSC controller, using the self-test and a substitute antenna.