How Big Is A Search And Rescue Transponder (SART)?

Search and Rescue Transponders are electronic devices that grab the attention of nearby vessels by painting a distinctive pattern on their radar screen. In an ideal world, everyone would carry one. On a small boat, however, space can be a real issue. So, how big is a Search and Rescue Transponder?

A typical SART is around 1 ft (30cm) tall, with a normal weight in the region of 0.5 kg. They often come with a telescopic pole that extends the height of the SART to about 1m.

How big are different SARTs?

All SARTs are very similar in size. I have compared a few of the most popular brands below:

Name	Height	Pole Length	Weight
McMurdo SmartFind S5A AIS SART	29.5cm	1.05m	583g
ACR Pathfinder PRO SART	22.7cm	Unknown	440g
SIMRAD SA70 SART	25cm	Unknown	482g
Tron SART20 Radar Transponder	25cm	Unknown	482g
SevenStar S.701 SART	33cm	Unknown	390g

From the table, you can see that they are all quite similar, hovering around the 1ft (30cm) length. The smallest is the ACR Pathfinder Pro at 22.7cm, but the body itself is somewhat dumpier than the others. Once you get up to the longest SART, the SevenStar S.710, the body is much longer and thinner.

In terms of weight, again they are all very similar. The difference between the lightest (390g) and the heaviest (583g) is less than 200g. The heaviest SART could even be dropped down to 283g if you exclude the weight of the mounting pole.

If you are selecting the size of SART appropriate for your boat, they are all broadly similar. The only way size should be a consideration is if you have a particular storage location in mind. Otherwise, there is not enough of a difference in size to make that your primary consideration when choosing your SART.

Are bigger SARTs better than smaller SARTs?

The physical size of the SART doesn’t have an effect on its performance. The biggest impact on its performance will be its mounting height. The higher you can mount the SART, the better its performance is going to be.

A lot of SARTs come with a pole that gives you an extra 1m in height. The pole can be useful, but you do need to think of it in context.

If you are using the SART on your boat, are you really going to stand there holding it on the end of a 1m pole? Probably not. I would think it is far more likely that you would attach it to a halyard of some sort and hoist it up into the air. There is an eye at the top of the body of the SART specifically designed for that.

Similarly, if you are using it in a liferaft, would you mount it on the end of its 1m pole? Maybe. Another option, though, is to hang it in the top of the liferaft from its eye. Chances are that the roof of the liferaft is more than 1m above the height of the floor anyway. The pole itself will only give a good advantage if you are holding it higher than it could otherwise hang.

Finally, what if you had it in a lifeboat? You could use the mounting pole to give it some more height. In this instance, you could lash the mounting pole to the end of an oar and give it a lot of height above the lifeboat. Think of it in context though. If your boat is big enough to carry lifeboats, the storage considerations of a pole with your SART will be insignificant anyway.

What is the smallest SART I can buy?

The lightest SART that you can but is the SevenStar S.701 SART. It weighs 390g and has been designed with liferaft activation in mind. This means that it has been designed to be small enough to fulfill the carriage requirements of a life-raft SART. 

Ro-ro passenger vessels need to carry 1 SART for every 4 liferafts. You can read more about that in this article where I discuss how many SARTs ships need to carry.

Despite being the smallest, it is not significantly smaller than any of the other SARTs on the market. When deciding which one you can buy, the weight and size don’t need to be your main consideration.

Is a SART bigger than an EPIRB?

SARTs and EPIRBs are broadly similar in size. The main difference between them is that the EPIRB is designed to float in the water. Its body is usually wider in the middle so that it maintains enough stability to float upright.

The SART is designed to be suspended in the air, so is usually longer and thinner than the EPIRBs.

In terms of weight, EPIRBs are usually slightly heavier. Again, this is often down to their stability when floating in the water. They can afford to have slightly heavier batteries, lower down, to keep themselves upright. 

Additionally, EPIRBs are only one method of using satellites to signal for assistance at sea. If you want a smaller and more portable version, you can consider a PLB. PLBs are smaller than both EPIRBs and SARTs, so are a good choice for a beacon to carry on your person.