AIS - transponder or receiver only?

[Birdseye]

thinking of installing an AIS but the shops I talk to all suggest a transponder. Instinctively, I prefer not to be indentified by the authorities. Having a transponder on a yacht is a bit like having one on a car announcing your speed to plod.

Am I just being paranoid?

Is there any real advantage to transmitting AIS data. After all big ship radars will see you and if you have radar yourself as well as AIS receive, you will see them in time to avoid them.

 

[Giblets]

The only advantage I can see with an AIS transponder is that those at home can see where you are on t'internet (being flippant there as I am sure there are other uses!). A mobo on a recent Channel Patrol tv programme got caught for passing through the exclusion zone in front of a box boat coming out of Southampton. He was holed up in West Cowes Marina but was traced by his AIS.

I would prefer an active radar reflector (Sea-Me but others available) when near big boats.

 

[Robin]

thinking of installing an AIS but the shops I talk to all suggest a transponder. Instinctively, I prefer not to be indentified by the authorities. Having a transponder on a yacht is a bit like having one on a car announcing your speed to plod.

Am I just being paranoid?

Is there any real advantage to transmitting AIS data. After all big ship radars will see you and if you have radar yourself as well as AIS receive, you will see them in time to avoid them.

Well I could see times I woul prefer to remain incognito but wanted a transponder version in case the septic's homeland security paranoia forced all boats to transmit so fitted one as part of our full systemelectronics upgrades. However we fitted a GARMIn 600 which can be fitted with a separate on/off toggle switch that prevents transmission if that is what you wish, switch 'on', transmit is off, switch 'off and transmission is normal.

I thought there might be a time when in some areas of the caribbean perhaps we might not want to be telling wannabe drug runners there was a nice US registered saily boat just a few miles away that they could maybe hijack and use to transport their wares to the mainland. likewise if returning from say the Bahamas/offshore, why make it easy for the 'poop police' to pick on us as the target of their duty shift to inspect that we had all our cocks suitably locked off to prevent unlawful overboard discharge inside the 3 mile limit. We will always comply, but one local boat was a little tardy doing so got inspected 2 miles out and was fined $400 because on a lumpy night returning from well offshore they had forgotten to re- cable tie the Y' valve to lock it in the 'holding tank only position.

 

[westhinder]

When I bought AIS six years ago, I chose a receiver only as it was quite a lot cheaper than a transponder. If I were to buy again, it would be a transponder. Anything that helps to make your presence known to other boats or ships in less than ideal weather must be a plus. As far as I know, most sets enable you to switch off transmission, so if sending your details is unnecessary or unpractical, or if you're feeling paranoid, you just flick a switch.
It is so much easier to contact another ship if there's any doubt about their intentions if you have the AIS-information, why not offer them the same convenience and add to your own security?

 

[laika]

I would prefer an active radar reflector (Sea-Me but others available) when near big boats.

Dual band sea-me is about £695 though which is rather more than the difference between receive-only AIS and a receive+transmit.

My transmit is off most of the time, only getting turned on for crossing traffic or poor visibility when the more things i have to let people know I'm there the better.

 

[johnalison]

I don't think anyone should feel that they "ought" to have a transponder. For many of us, it's just a way of using up surplus cash.

I have a transponder, on the same general grounds as westhinder - just another way of making oneself seen - but I already have a SeaMe and radar. Given the need to choose, I would acquire these items in the order 1) SeaMea or equivalent, 2) Passive AIS, 3) Transponder.

Yes, it's great fun for friends and family to follow one's progress, and it can be good when cruising in company, but I think most of us will have acquired a transponder as an additional means of collision avoidance.

 

[AliM]

We had a receiver only for the last 3 years on our present boat and about 4 years before that on our previous one. We have now upgraded to a transceiver. We only feel the need to transmit when we are in poor visibility or when crossing shipping lanes, and have installed a switch to allow us to be in silent mode the rest of the time (it can also be done from the chartplotter).

The thing that made us decide to upgrade was when we were crossing between Sweden and Denmark, sailing in quite lively conditions and we saw on AIS that we were on a collision course with a ferry. We called it, and it seemed to have trouble identifying us (despite us having an active radar reflector). There have been other times when transmission would have been helpful too. The AIS receiver has been invaluable, though.

If you decide on a receiver only, you may like to buy our old one - see the for sale forum!

 

[Peroo]

We had a receiver only for the last 3 years on our present boat and about 4 years before that on our previous one. We have now upgraded to a transceiver. We only feel the need to transmit when we are in poor visibility or when crossing shipping lanes, and have installed a switch to allow us to be in silent mode the rest of the time (it can also be done from the chartplotter).

The thing that made us decide to upgrade was when we were crossing between Sweden and Denmark, sailing in quite lively conditions and we saw on AIS that we were on a collision course with a ferry. We called it, and it seemed to have trouble identifying us (despite us having an active radar reflector). There have been other times when transmission would have been helpful too. The AIS receiver has been invaluable, though.

If you decide on a receiver only, you may like to buy our old one - see the for sale forum!

6 years ago we went for, well could only afford, a receiver, and its been great. Now we would consider a transponder after 6 years crossing seas and oceans. However we have noticed that the majority of yachts with AIS transponders we came across did not update their details, other than being a yacht of a certain size and doing a certain speed, which we could determine via AIS anyway. Not entirely sure what the benefit of this approach was.

We have also come across a number of commercial vessels who switch their AIS off, cruise liners being one of the worst group, particularly at night when they are deceiving their passengers that they are sailing vast distances to their next exotic location, or trying to - I mean, St. Vincent to Castries!!!!

We also installed a SeaMe.

 

[pagoda]

6 years ago we went for, well could only afford, a receiver, and its been great. Now we would consider a transponder after 6 years crossing seas and oceans. However we have noticed that the majority of yachts with AIS transponders we came across did not update their details, other than being a yacht of a certain size and doing a certain speed, which we could determine via AIS anyway. Not entirely sure what the benefit of this approach was.

We have also come across a number of commercial vessels who switch their AIS off, cruise liners being one of the worst group, particularly at night when they are deceiving their passengers that they are sailing vast distances to their next exotic location, or trying to - I mean, St. Vincent to Castries!!!!

We also installed a SeaMe.

I was on the bridge of a car ferry last year, and asked those on watch what they thought about AIS. They are obliged to transmit, by virtue of their tonnage, bu they pay it virtually no attention. They rely mainly on radar and eyesight of those on duty. They have Chan 16 on in the background, but pretty quiet, since very few ships these days carry actual RO as crew. Further discussion with a friend who is a bridge officer with Cunard leads me to think almost all the focus of training is still on RADAR. Which almost makes sense from a big ship perspective. What worries them most is other LARGE masses of steel charging along at 20Kts, not a few tons of nearly invisible plastic doing 6Kts.
I have an AIS receiver, which I have found useful for spotting commercial traffic at fairly high speeds, at a respectable distance. Having the display cluttered by pleasure craft is not a huge help at all...
So work out what YOUR priorities are - and spend your dosh accordingly. (or not, as the case may be). I would not place any faith whatsoever on a yacht transponder being noticed by anybody, except perhaps other small craft - and those ashore in armchairs with the internet handy!!

 

[sailorman]

I was on the bridge of a car ferry last year, and asked those on watch what they thought about AIS. They are obliged to transmit, by virtue of their tonnage, bu they pay it virtually no attention. They rely mainly on radar and eyesight of those on duty. They have Chan 16 on in the background, but pretty quiet, since very few ships these days carry actual RO as crew. Further discussion with a friend who is a bridge officer with Cunard leads me to think almost all the focus of training is still on RADAR. Which almost makes sense from a big ship perspective. What worries them most is other LARGE masses of steel charging along at 20Kts, not a few tons of nearly invisible plastic doing 6Kts.
I have an AIS receiver, which I have found useful for spotting commercial traffic at fairly high speeds, at a respectable distance. Having the display cluttered by pleasure craft is not a huge help at all...
So work out what YOUR priorities are - and spend your dosh accordingly. (or not, as the case may be). I would not place any faith whatsoever on a yacht transponder being noticed by anybody, except perhaps other small craft - and those ashore in armchairs with the internet handy!!

That sums it up well

 

[pvb]

I reckon the ideal order of preference is an AIS receiver (ideally interfaced with the plotter and VHF), then an active radar enhancer, and (if you really must) an AIS transponder. There's obviously lots of sales pressure to go the transponder route, as it's very profitable business for retailers, but you have to bear in mind that there are extremely marginal safety benefits as ships can, and do, filter out Class B AIS transmissions, so there's no guarantee you'll be seen. Having said that, I can understand that some people like to have a means of being tracked by their families when they're close to shore. But most AIS transponders seem to be fitted by the "look at me, I've got an AIS transponder" brigade, who also seem to leave them switched on in marinas.

 

[lpdsn]

Having the display cluttered by pleasure craft is not a huge help at all...

+1

The CPA alarm function would be really useful but for the yachts that transmit.

Still, the clusters of them give a distance and bearing to the nearest marinas.

 

[Resolution]

Like some others on this thread I went for AIS receiver only, about six years ago. I used to sail in the Solent and did not wish to add to the clutter.

Two years ago we crossed the North Sea in thick fog and a lumpy sea, and the AIS receiver was vital in weaving our way across the shipping lanes. Even with our radar on I would not guarantee that we were a visible blip on other ship's radars, given the sea state. I wished very much that we had also the AIS transmitter.
Last year we were cruising in company in the Med with a few other yachts and we found it very helpful to be able to identify them at a reasonable range via their AIS transmissions.

So yesterday I placed the order to replace the receiver-only unit with a new transmitter/receiver.

 

[johnalison]

That sums it up well

I don't know when you go to sea but I'm usually lucky to see a couple of yachts when I cross the Channel or N Sea. Even up and down the Wallet I can't see a problem even if all yachts transmitted - I would simply change the scale on the plotter.

 

[Lucky Duck]

I don't know when you go to sea but I'm usually lucky to see a couple of yachts when I cross the Channel or N Sea. Even up and down the Wallet I can't see a problem even if all yachts transmitted - I would simply change the scale on the plotter.

It is certainly a problem on the Orwell, where I am currently berthed three or four boats seem to have their AIS on permanently

 

[sailorman]

It is certainly a problem on the Orwell, where I am currently berthed three or four boats seem to have their AIS on permanently

that narrows it down to Woolverstone or SHY.
Its the Look at wot i have just bought syndrome

 

[bitbaltic]

I reckon the ideal order of preference is an AIS receiver (ideally interfaced with the plotter and VHF), then an active radar enhancer, and (if you really must) an AIS transponder. There's obviously lots of sales pressure to go the transponder route, as it's very profitable business for retailers, but you have to bear in mind that there are extremely marginal safety benefits as ships can, and do, filter out Class B AIS transmissions, so there's no guarantee you'll be seen. Having said that, I can understand that some people like to have a means of being tracked by their families when they're close to shore. But most AIS transponders seem to be fitted by the "look at me, I've got an AIS transponder" brigade, who also seem to leave them switched on in marinas.

+1

We've got the most basic AIS, a digital yacht USB box which talks to a little old netbook which serves as a plotter. As we are coastal potteries and I always feel most comfortable with paper Nav, said box is only on a) in poor Vis, b) when there is lots of traffic about (rare in the Bristol Channel) or c) when SWMBO is navigating.

AIS is a cracking tool because you get point and time of closest approach from the big boats. As a skipper my gut reaction on first installing it was, hell, if I'm the stand on vessel then this will make me more certain to stand on the ColRegs. But all previous experience especially in busy waters off Copenhagen said to me, big boats don't care if you sand on the ColRegs, they hold course and start honking. So I figured an AIS receiver is great because it allows you to see a collision situation developing so far in advance that almost anything you do will remove it; that is, you can sail defensively.

I for one am sure that if I upgraded to a transponder I would be thinking about standing on my ColRegs rights again. The big boats haven't changed though, so for me I worry that a transponder would lead me to sail more confidently into potential collisions that I would have otherwise avoided.

So for me, AIS is about proactive defensive sailing with a receiver. Proactive safe sailing in situations where both vessels need to consider their ColRegs position is better achieved with a radar transponder when the other boat is likely to be very much bigger than you.

Cheers

 

[sailorman]

I don't know when you go to sea but I'm usually lucky to see a couple of yachts when I cross the Channel or N Sea. Even up and down the Wallet I can't see a problem even if all yachts transmitted - I would simply change the scale on the plotter.

i have set up my system to only "see" vessels@ 10 mls, quit good enough for shipping but yachts thats the best part of 2 hrs away

 

[Mike k]

AIS is quite useful to identify the ships name of vessels heading towards you if you need to call them up.

 

[Lucky Duck]

that narrows it down to Woolverstone or SHY.
Its the Look at wot i have just bought syndrome

Those two establishments appear to be the worst culprits for that kind of thing. It means the alarm doesn't usually get switched until I'm past Pye End