Emergency position indicating radio beacons and search and rescue radar transponders
406 MHz EPIRB
The 406 MHz EPIRB is a float-free satellite distress beacon detected by COSPAS-SARSAT. It transmits a unique beacon ID (usually linked to the vessel's MMSI) and, with GNSS, a position. It also transmits a 121.5 MHz homing signal for aircraft/SAR direction finding. It must be registered with the national administration; registration must show the correct vessel, owner, emergency contacts and MMSI. The battery and hydrostatic release unit have expiry dates and must be replaced.
SART
The Search and Rescue Radar Transponder operates in the 9 GHz (X-band) marine radar band. When interrogated by a radar, it returns a series of 12 dots on the radar display, helping locate the survival craft. It should be mounted about 1 m above sea level in the craft and switched on when abandoning ship. It does not alert a satellite or a coast station; it is a local locating device.
Worked example
An EPIRB is fitted with a valid battery but the registration still names the previous owner and an old MMSI. Reasoning: the beacon will alert, but the RCC may contact the wrong people and may not know the vessel. The EPIRB registration must be corrected before the voyage. A hydrostatic release within its expiry does not cure incorrect registration.
Traps
Do not confuse EPIRB (satellite alerting) with SART (radar locating). Do not test a 406 EPIRB by activating it over water; follow the manufacturer's self-test. Do not stow the SART where it cannot be reached. Do not assume the HRU will release if it is painted or seized.