Radio Equipment Maintenance, Fault Diagnosis, and Batteries
The exam tests the SOLAS maintenance philosophy, battery care numbers, and a logical fault-finding sequence rather than deep electronics.
Maintenance options (SOLAS IV/15)
At-sea maintenance may be met by duplication of equipment, by shore-based maintenance, or by at-sea electronic maintenance capability. The chosen method must be recorded and available for inspection. Spares, manuals, test equipment and maintenance records form part of the requirement.
Reserve source of energy
Batteries must supply the GMDSS for at least 6 hours, or 1 hour where an emergency generator supplies the GMDSS. They must be independent of the main propulsion and emergency switchboard, protected against overcharge and deep discharge, and ventilated against hydrogen.
Lead-acid battery numbers
- Specific gravity about 1.28 fully charged; falling towards about 1.15 when discharged. Check monthly and record.
- Typical float voltage: 13.5–13.8 V for a 12 V battery, about 27–27.6 V for 24 V.
- Top up with distilled water only, never acid; do not overfill; keep terminals clean and lightly protected.
- Capacity is proved by a discharge test, not by voltage alone.
Fault-finding sequence
No transmit: check supply and fuse, then antenna and feeder, then earth, then test into a dummy load. If output is normal into the dummy load but not on the antenna, suspect the antenna system. High VSWR points to a feeder/insulator/earth fault. DSC not transmitting: check the Ch 70 antenna, the position input and the DSC self-test. Inmarsat will not log on: check antenna obstruction, elevation/azimuth and the correct ocean region. EPIRB self-test failure: check battery and HRU expiry dates.
Worked example
MF/HF shows low forward power and high VSWR. Connect a dummy load: if power is normal, the transmitter is healthy and the antenna/feeder is faulty. Inspect the insulator, coax and earth; repair and retest. Record the fault and action.
Traps
- Topping up with acid or overfilling cells.
- Judging battery capacity from voltage alone.
- Testing transmitters on distress frequencies instead of a dummy load.
- Ignoring EPIRB/SART battery and HRU expiry dates.