EPIRBs, SARTs and Battery/Antenna Care
EPIRB: what it does and how it is registered
A 406 MHz EPIRB transmits a digital distress alert carrying the vessel's identity and, on GNSS models, its position, to the Cospas-Sarsat satellite system; a 121.5 MHz transmitter provides homing for rescue aircraft and boats. It is registered to a vessel and a responsible person with emergency contacts. Registration is not a formality: an unregistered beacon produces an alert with no name, no callsign and nobody to telephone. Float-free models sit in a bracket with a hydrostatic release so they activate if the vessel sinks, and they can also be switched on by hand. Test only as the manufacturer instructs - commonly a self-test within the first five minutes of a UTC hour - and respect the battery expiry date on the label.
SART: the radar answer
A SART is a 9 GHz (3 cm) radar transponder. When swept by a vessel or aircraft radar it replies with a line of twelve dots on the screen, giving range and bearing to the casualty. It transmits no position of its own and is useless unless a radar is looking for it. Mount it as high as possible in the liferaft, at least a metre above the water and clear of the canopy, and switch it on when survivors and rescuers are likely to be close. Its battery is rated for roughly 96 hours on standby and 8 hours of replies.
Batteries and antennas
Handheld batteries are usually lithium-ion: charge before every passage, do not leave them flat or in a hot cabin, and carry a spare or a pack that accepts disposable cells. Fixed sets need a healthy 12 V supply with clean, tight terminals. The antenna and its coax matter more than the set: a masthead aerial with good height beats a bigger transmitter, and a corroded PL259 plug or water in the coax will destroy range. Never press PTT with the antenna disconnected.
Worked example
At sea you knock the EPIRB off its bracket and it begins flashing. Reasoning: it may already have transmitted. Switch it off immediately, then call the coastguard on Ch 16 or by DSC with the vessel name, MMSI and position, state clearly that it was an accidental activation, and ask them to cancel the alert. Do not simply stow it and hope; an unexplained 406 MHz alert launches a search.
Traps
- Testing an EPIRB outside the permitted window or for too long.
- An EPIRB still registered to the previous owner.
- Switching on a SART inside the cabin where radar cannot see it.
- Antenna connections left to corrode over winter.