EPIRB and Search and Rescue Radar Transponder (SART)
EPIRB
A 406 MHz COSPAS-SARSAT EPIRB alerts the SAR system through satellite and carries a registered identity; many also transmit GPS position and a 121.5 MHz homing signal. It should be float-free, mounted where it can escape a sinking vessel, with a hydrostatic release unit and in-date battery. Registration details must match the vessel and be updated when ownership or details change.
SART
A radar SART operates in the 9 GHz X-band and responds to a searching radar with a characteristic series of dots on the radar display, commonly described as 12 dots. It is detected by radar, not by satellite, and its range depends on radar height and antenna performance. An AIS SART transmits an AIS target and is a different device.
Testing and activation
Use the built-in self-test, not a live transmission, to check an EPIRB. Activate a SART only in a real emergency or under controlled test conditions with the radar interrogating it. If an EPIRB is activated accidentally, switch it off, inform the coast guard immediately and cancel the alert.
Worked example: an EPIRB is knocked from its bracket and starts flashing. Switch it off, notify the coast guard by VHF and give the vessel identity and position. The reasoning: the satellite system may already have passed the alert to an SAR centre, so cancellation is as important as stopping the transmission.
Traps
A SART is not detected by satellite and an EPIRB is not a radar transponder. Do not test an EPIRB by live activation in the water. Check battery and HRU expiry dates. Do not assume a 121.5 MHz homing signal replaces the 406 MHz alert; it is a homing aid.