What is a SART?
SART stands for Search And Rescue (Radar) Transponder. Its purpose is to assist in the location of survival craft, or vessels in distress. It is the principal means of homing in the Global Maritime Distress and Safety System (GMDSS). It allows any vessel or aircraft equipped with marine band radar to detect and locate the survivors at a range of up to 5 nautical miles from a surface vessel, or perhaps 30 nautical miles from an aircraft, depending on its altitude.
All big ships on international trade are required to carry SARTs for use in liferafts, as well as for emergency location of the main vessel. In the majority of cases, two SARTs are carried, one each side of the bridge, mounted where they can be easily reached if abandoning ship.
To give the required detection range, the SART needs to be operated at least 1 metre above the water, so suitable arrangements have to be made for erecting the SART on the survival craft. A SART may be supplied with a telescopic pole which is pushed out through a hole in the liferaft canopy with the SART perched on top. A less precarious arrangement which has proved just as effective is to hang the SART inside the raft using a rope or strap passed over the canopy support tube.

How does a SART work?
When the SART receives a valid signal, it switches into Transmit mode, and responds to each valid signal by transmitting a series of twelve (12) sweeps through the band 9,200 to 9,500 MHz, each transmission lasting just over 100 microseconds in total. This signal is seen on the passing vessel's or aircraft's radar screen as a line of twelve dots, with the SART position being given by the closest dot. This is a clear, unmistakable, Internationally recognized signal, and shows the presence AND location of a vessel, survivor or life raft with an active SART.

Why do I need a SART?
Whilst they are not mandatory for leisure vessels it is well worth considering including a SART in your safety equipment.  A SART may be activated in "situations of grave and iminent danger" and, because it puts an internationally recognised signal on the radar screen, it can be used, in addition to a radio call, to ask for help.

Comparison Table

	SevenStar S.701 SART	Jotron Tron 9 GHz SART	McMurdo S4 Rescue SART
Frequency	9.2-9.5 GHz	9.2-9.5 GHz	9.2-9.5 GHz
Dimensions	Length 332mm x diameter 40mm	Length 370mm x diameter 85mm	Length 264mm x diameter 90mm
Weight	390 g	1050g	530g
Battery Capacity	96 hrs standby + 8 hrs continuous operating when activated by radar with 1 KHz prf.	96 hrs standby + 8 hrs continuous operating when activated by radar with 1 KHz prf.	96 hrs standby + 8 hrs continuous operating when activated by radar with 1 KHz prf.
Response Delay	Max 0.5 µs	Max 0.5 ms	Max 0.5 µs
Radiated Power	Not less than 400 mw (+26 dBm)	Not less than 400 mw (+26 dBm)	Not less than 400 mw (+26 dBm)