SART stands for Search And Rescue Transponder.
Unlike an EPIRB (Electronic Position Indicating Radio Beacon) which independently broadcasts a radio signal for satellites to repeat to a ground station, a SART only broadcasts a response signal when it is interrogated by radar. Both have a useful purpose and they are generally used in conjunction with each other.
An EPIRB is a great way to send a distress message, even when thousands of miles from shore. The signal will be picked up by satellites that will be able to broadcast the position of the EPIRB to a ground station. From there, a co-ordinated rescue mission can be instigated.
A Search And Rescue Transponder, on the other hand, only broadcasts a signal when activated by the pulse of a radar. Both pieces of equipment are battery operated and therefore have a limited life.
In simple terms, an EPIRB ‘raises the alarm and indicates a position’ and the SART is used by rescue craft searching in that area. The idea being that once a transponder is identified by the 12 pulses it sends on being interrogated, rescue services can ‘zero in’ on the SART as the 12 pulses increase in frequency.
SARTs operate at 9GHz, Unlike EPIRBS which broadcast at 4.6 GHz. They have a typical battery life of about 96 hours when activated and on standby and 8 hours once being interrogated. Therefore, the best way to use a SART is to activate it once you consider SAR craft are in the general locality. The SART will then help to guide SAR to your exact location.