Sartech - Specialists in Search and Rescue Technology

• What is a SART?
• How does it work?
• Should I carry a SART on my boat?
• How do I choose which SART to buy?
• Why should I buy from Sartech?
• Should I buy a SART instead of / as well as an EPIRB?
• Can I test it to see if it works?

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.

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How does it work?

Navigational radar works by bouncing pulses of radio energy off distant objects and measuring how long the response takes to return. The radar antenna fires out these pulses with a very narrow beamwidth from a rotating antenna, so at any one time the radar can tell from what direction the returns are coming - i.e. the bearing of the target. The time taken for the radar pulses to return gives the range of the target; the bigger the delay, the longer the range.

The radar thus produces a plan view of the coast and other passive targets around the radar-equipped vessel. In good conditions, a liferaft would be visible on a ship's radar at a range of several miles, but factors such as reeflections from waves and falling rain can make it very difficult to spot such small objects.

The SART is a transponder, which means it is a transmitter that operates in response to receiving a radar pulse. If that was all it did, then it would be only amplifying the return, giving a brighter dot on the screen. What it actually does is produce a total of 12 returns for each radar pulse, with a delay between each one. This then appears on the radar screen as a very distinctive line of 12 dots, leading away from the position of the SART (the radar thinks that the delayed pulses are reflections from more distant objects).

In the example shown, there is a SART located approximately 5 range rings out from the centre of the radar plot, on a NW bearing.

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Should I carry a SART on my boat?

Some commercial vessels are required to carry SARTs as part of their mandatory safety equipment. Contact your local authorities to check if this applies to you.

Otherwise, you should probably give priority to fitting a 406MHz EPIRB, as this will give you a world-wide emergency alerting capability, providing the rescue forces with your identity and position to within a couple of miles. Adding a SART will give you the additional ability to be readily located by any radar-equipped vessel.

A SART may be activated in "situations of grave and imminent danger". You may consider it a worthwhile item to carry if you plan to cross shipping lanes in a small vessel. Should you get into trouble and be in danger of being run down, activating the SART should quickly get the attention of the watchkeeper on the approaching vessel.

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How do I choose which SART to buy?

The following points should be borne in mind before getting down to price and delivery:

Approvals

Most SARTs are type approved to national or regional specifications based on IEC 61097-1 and the environmental test standard IEC 60945. There are only minor regional variations. However, especially when buying mail order or via the internet, make sure that your chosen SART is approved by the authorities where your vessel is registered.

In Europe you will be OK if you buy a SART with the new "wheelmark" approval, showing that it is approved in accordance with the Marine Equipment Directive.

Look for this mark:

In the USA, SARTs must be approved by the Federal Communications Commission (FCC). Look for the "FCC ID" to check this.

Cost of ownership

Bear in mind that all SARTs have a limited battery life. After 4 or 5 years, depending on model, the SART will need to be sent to a service depot to have a new battery fitted and be fully tested. Checking out the cost and availability of service facilities in your area might be a good idea before making your decision. Some manufacturers offer a service exchange facility for a quick turn-round. Normal warranty period is 12 months - however Sartech offers a l0 year warranty on all SARTs bought direct.

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Why should I buy from Sartech?

We are the specialists, so we can advise you on the right equipment for your needs and provide you with continued support for all the time you own it. We are so confident in the equipment we supply that we now offer a 10 year warranty, so if your SART ever fails its self-test, you can just send it to us for repair or replacement. If you take it back to any other supplier once the manufacturer's 12 month warranty has expired, then you could be faced with a big repair bill.

We carry out ISO9000 manufacturer approved servicing in-house and manufacture our own battery packs, so most servicing and repairs can be turned round in days, not weeks.

Sartech aims to offer the best prices by selling direct, but you may find cut-price deals elsewhere. Call us first before being tempted by such special offers. You could end up with a lower specification or obsolete product - you certainly won't be getting our level of after sales support! We can match or even beat anyone else's prices - if you don't want our 10 year warranty.

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Should I buy a SART instead of / as well as an EPIRB?

A SART is not an alternative to an EPIRB. It is not designed to raise an alert, but allows any vessel carrying a normal marine radar (X-band) to come to your aid even in very poor visibility. Once activated, the SART causes a series of dots to appear on the radar screen of any vessel within a range of about 5 nautical miles. These dots are quite distinctive, and stand out from the normal radar responses - giving the search vessel both the bearing and range to the SART.

The SART is an ideal complement to the ship-to-shore alerting devices such as EPIRBs, INMARSAT-C, and DSC radio. These devices tell the SAR forces who you are and give your approximate position - but this is of no help to you if you are in an area where there are no dedicated SAR resources. For instance, if you are off the coast of East Africa, or in the middle of the ocean, your best hope for a rapid rescue may be a merchant vessel, cruise liner, or even a fishing boat. Nearby vessels can be informed of your problem and your whereabouts, but they will not have the means to home in your EPIRB. In poor weather conditions, it can be very difficult to locate a liferaft with a visual search, even if you can come to within a couple of hundred metres by using an accurate GPS fix. The SART gives any radar equipped vessel the means to detect and locate survivors.

If you never stray beyond 'home' waters, well served by Coast Guard, Lifeboats etc., then you don't really need a SART. Those going further afield should certainly consider carrying one.

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Can I test it to see if it works?

A test can be done in port in conjunction with a vessel's own radar, or with the radar on a nearby vessel, provided that the duration of the test is kept to the absolute minimum time to avoid any disturbance to other vessels. Such tests should be coordinated with the local harbourmaster and/or coast guard.

Set the radar to a 12 mile range (or thereabouts) and turn the gain up. Switch off filters such as Sea Clutter and Rain Clutter and switch on the SART at least 20 metres away from the radar scanner. It will not need to be directly in the beam of the radar, but should have a clear line of sight to the scanner, and should ideally be in an open area away from reflecting surfaces.

You should expect to see a series of concentric rings around the radar screen. This is due to the short range, with the SART responding to and being detected by the radar scanner throughout its rotation, even when pointing in the opposite direction. Turn the gain down, and the rings will probably narrow to a series of arcs. Only at longer range will the characteristic dots be seen, due to the width of the radar beam.

This kind of test gives a good deal of confidence that a SART is working properly, but even a SART with poor sensitivity and/or low output will work at short range. SARTs should also be checked that they are correctly tuned, as they need to be compatible not only with marine radars but also with airborne radars. A properly equipped service centre will not only change the battery in your SART, but will be able to fully test its performance and provide you with printed test results.

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