What is SART? and it's purpose.

So you've entered your Survival Craft, but now you need to be rescued. Even with ship searching in the correct area, narrowing down your exact location can be a real challenge. That's where a SART can help.

They attract the attention of passing vessels by actually drawing on their radar screen.

Activated correctly they Point searcher in the right direction increasing your chances of being rescued.

SART stands for search and rescue transponder. It is an active device, meaning it transmits a signal to draw attention to itself. It's triggered when it detects a pulse from a radar as soon as it does. It transmits multiple pulses straight back painting a series of 12 distinctive Echoes on the screen, guiding the searching vessel towards its location. They operate at 9 GHz, which means Show up on an x-band 3 centimeter radar screen. Day to day, the unit's themselves require very little maintenance. 

All you need to do is make sure they're clean and dry, check battery  expiry date and test them monthly.

Every unit is different so you do need to check the instructions on this unit. You can just slide the switch to the test position to temporarily activate it it will indicate whether the internal test is successful often with a light if you have radar you can also check The screen to check it responding correctly an actual emergency. You need to make sure you take it with you. There's no rush to activate it. Especially if you're still close to your original vessel, that will paint a large echo anyway and may even block the SART transmission. 

Once you are clear you can then set it up to activate the SART. You normally just need to remove a pin. It should then indicate to you that its working. Once activities, needs to be mounted as high as possible. The higher it is the further away. It will be detected. In the water you can expect only a mile or so on the floor of the life rafts not much better, maybe 2 or 3 miles if you're lucky, but mounting 1 meter high it must be able to be detected at least 5 miles away. 

One meter is the height of IMO performance standards and it should have been designed to comply with that.

It should have enough battery to last 96 hours in standby mode has 4 days and 8 hours in transmission mode. Of course, it should only actually be in transmission mode when another vessel is close enough to detect it. If you have multiple SART, it's important to only activate one at a time. Using one ensure  that the  radar return maintains its distinctive nature and can't be confused with another Echo.

The other point to note is to never use a SART and a radar reflector close together. There's always a chance that the radar reflector will block the SART signal once it's all set up. You just need to wait for a radar to be close enough to activate the SART.

The approaching vessel the first sign that says start operating is a characteristic dots on their radar screen. At long-range the shows 12 dots in a line, originating from the start location. The first return is SART itself and the further dots the extra echos generated by the SART. The extra echos will be 0.6 miles apart, so they can be seen best on a six or 12 mile range setting as they will span a total of 7.2 miles across the screen.The precise range that the SART is detected does vary. We have already discussed about the importance of mounting height. Another major factor is the height of the radar looking for it surface craft with scan a height of 15 meters. You can expect those performance standards of five miles for a correctly mounted SART, this then increases the bigger ships with higher radar scanners. The greatest range will be from aircraft searching around 3,000 feet.They may pick it up at even 40 miles away. Once the SART begins generating these extra Echoes, It indicates to its user that is under interrogation.

often this is by flashing light or an audible signal. It tells the survivors that an x-band radar operating nearby and should have to somewhat of a morale boost. Knowing that there are vessels close by is also good indication that traditional flares will be spotted. Even at maximum range rocket parachute flare should still be visible to the vessel that as activated the SART. Hopefully now the SART, or maybe even the flares attracted the attention of the other vessel, they can use the shape of the echo to locate the survival craft as they draw nearer, the dots on their radar screen become arcs. This is because the scanner is picking up the returns across a larger angle. The closer it gets the larger the angle that the scanner can detect SART. So the larger the arcs become on the screen eventually the arcs become full circles showing that the approaching vessel is out very close to the SARTs location. If all goes well the Survivalcraft should be clearly visible that survivors can be rescued. 

They're not cheap. If you're popping in a life after need rescuing your wish you had one.