AIS Transponders for Yachties

[johnalison]

I leave mine on when in harbour so that my mates can find me, and go into "silent mode" when crossing shipping-lanes in case my course is perceived as not being sufficiently at right angles by Big Brother. Well, that's my story anyway.

 

[Blue5]

I can only assume you are talking about AIS receivers, they are brilliant and I cannot see why any small boat shouldnt have one. They cost pennies.

Class B transponders are rubbish. They sometimes show you up then you can disappear for long periods. I have one because it is a ORC class 2 requirement and have checked with other boats, commercial shipping and Falmouth coastguard and they all confirm the unreliability of class B. Its not just mine, that's about mid range it would seem, it's all types. We regularly check around the fleet so have some experience of this.

Class B transponders may not be perfect but they are only a "few pennies" more than receivers and any piece of equipment that makes you more visible is a plus in my book.

I assume ORC don't think they are rubbish either but anyway my choice I have one it stays on when on passage.

On a recent trip our shore contact was able to track us up the coast of Portugal and across Biscay, probably lucky to get a signal most of the way but the advantage is obvious.

 

[maby]

I must look to see if I can switch off yachtie transmissions, now and again. I seem to only pick them up at well under 2 miles anyway, but it can be useful.

I got mixed up with a Figaro fleet of siglehanders this year. I was going downwind, on port tack, at an angle designed just to fill the genoa. The fleet were slanting across me, hard on the wind, on starboard, doing about 8kts, I was, maybe doing 3. The AIS was quite jolly, showing most boats missing me by miles. The time to CPA was (I think) about 6 minutes when first picked up. Six minutes does not give you a lot of time to put the kettle on. For the first boat forecast to meet me head on I turned left and he passed ahead, quite close.
For the second, I dallied a bit and weighing the job up decided I would pass in front, esp if I nudged a bit to starboard. This is a schoolboy error. With seconds counting down I could see how he was hunting around, following the wind. One moment he was heading for my midship the next passing clear, if the wind had backed a fraction he would have taken off my bow. There was a lot of thought compressed into the last 30 seconds but he passed 60 feet clear.

I was able to inspect the deck arrangements of the second boat in close detail. Indeed there was not a soul in sight on either boat.

I cannot turn off specific classes, but I can mask anything stationary, or several miles away.

 

[myquest]

Tell that to the three (so far) that we've had calling mayday (for genuine reasons) when being able to track them on AIS has been invaluable for both us and the lifeboat.

Does the lifeboat get many callouts to the marina? I'm being flippant of course, but it doesn't change the fact that dozens of targets in a marina is of no assistance to anyone.

 

[SolentBoat]

Is it a problem if the AIS is cluttered in the Solent? It's so busy with non-AIS boats that you're best off turning off the AIS and using your eyes anyway.

 

[fireball]

The moment you have chosen is hardly typical

No but if many more yachts get ais b then it will soon be!

So turn off ais display when it's too cluttered. What's the problem? As per my earlier argument, how does this differ to a radar return?

You can tune radar down - filtering out the dross - not so easy with many cps

 

[fireball]

I cannot turn off specific classes, but I can mask anything stationary, or several miles away.

Yup handy on the stationary ones - but the ais b targets 2 miles away are of no interest but the ais a ones 3+ are!

 

[Jamesuk]

Speaking with a long distance sailor friend of mine who has one says there's no need for them round the coast except in exceptional circumstances like fog. Even crossing the channel we are supposed to keep out of the way.

Once out of the shipping lanes he said it was magic as large ships could alter course for him very early.

I must admit I tend to agree as the solent is rapidly turning into a mass of green triangles which can only get worse as these come down in price and become more popular.

I know I can turn off the yachtie category but that also kills stuff I may wish to see.

Any views ?

I think it is great - It is the Social networking of the Sea!!

 

[johnphilip]

On Off Switch?

Leisure craft with permanent AIS transmissions are indeed a menace. I assume they all get turned on as soon as an instrument main switch is activated? Why? Much better if it was linked to the navigation lights or switched separately. Just activate it in the circumstances it comes into its own, darkness, bad visibility or crossing a shipping lane.In these situations there are generally far fewer leisure boats about and ships have a good chance of noticing your marker.
Forgetting to turn the transmitter on when needed is unlikely, a lonely night or fog or ships approaching is a very effective prompt
I was a great believer in AIS, now it could be spoiled by this bombardment of signals

Guidance along these lines from YM or better from the RYA could save this great aid.

 

[dslittle]

Just activate it in the circumstances it comes into its own, darkness, bad visibility or crossing a shipping lane.
I was a great believer in AIS, now it could be spoiled by this bombardment of signals

I have a AIS transponder and hardly ever turn it on over than in the circumstances above. I have occasionally been 'annoyed' by the constant alarms as I have come into an area where there were a lot of dangerous targets and resolved the matter by turning my AIS off (I have no doubt that I contributed to that cluster of alarms). On the other hand I have watched a very large ship alter course by five degrees to go behind me in the Channel. Now that was very reassuring.
AIS is a great tool and aid to safety. As with all matters sailing, if used sensibly and with respect for others, I cannot see any argument against it - yes I know that Drake didn't have AIS or a Chartplotter or a Rocna or radar or a digital watch and managed to circumnavigate the world...

 

[DJE]

Isn't there a danger that the clutter of class B targets close to shore will cause big ship crews to filter them out. They may then forget to switch class B reception back on before they start meeting lone yachts crossing shipping lanes further offshore.
Thought I heard somewhere that French yachts aren't allow to switch on their transponders within 6nm of the coast. Seems like a good idea to me.

 

[KenMcCulloch]

Not a problem where we mostly sail. With regard to filtering out 'noise' our plotter has a setting to ignore all but dangerous targets , dangerous as in CPA closer than or in less time than settings you can choose.

 

[lw395]

Isn't there a danger that the clutter of class B targets close to shore will cause big ship crews to filter them out. They may then forget to switch class B reception back on before they start meeting lone yachts crossing shipping lanes further offshore.
Thought I heard somewhere that French yachts aren't allow to switch on their transponders within 6nm of the coast. Seems like a good idea to me.

How far from the coast was the Ouzo hit?

 

[tcm]

hi from pacific. The “unreliability" seems likely in more crowded waters like er well, in English channel, frinstance. In emptier offshore sea and ocean there are two sorts of things in the sea - unmarked things like fish and lumps of wood, and marked things like big steel ships. With an ais transponder you are in the second group, without it you are in the first.

I would like to know from a tech person the tech difference between ais A and B - stronger signal or what? I thin either for this boat (or another) I might/would get AIS A

I currently have AIS B and C so my C receiver can watch the the B transponder creep along behind us which is sortof interesting, ish...

 

[capnsensible]

When Im on a yacht with AIS I like it and use it a lot to pass the time.

When I am on a yacht without AIS I am unbothered.

 

[jay]

I can only assume you are talking about AIS receivers, they are brilliant and I cannot see why any small boat shouldnt have one. They cost pennies.

Class B transponders are rubbish. They sometimes show you up then you can disappear for long periods. I have one because it is a ORC class 2 requirement and have checked with other boats, commercial shipping and Falmouth coastguard and they all confirm the unreliability of class B. Its not just mine, that's about mid range it would seem, it's all types. We regularly check around the fleet so have some experience of this.

Thats because Class B has a far slower update interval than the stuff the comercial boys use. Plus remember its a low power VHF signal on line of sight so subject to the obvious limitations that entails.

 

[jay]

AIS is the best thing i bought in a long while, it's invaluable for crossing shipping lanes, fog, off shore racing etc. You can identify the ship that's on a close CPA and call them up, 9 times out of 10 you can resolve the situation satisfactorily for both parties.

For inshore i guess i would see what the conditions and other factors are then make a choice to whether you turn off the transmit.
These days friends and family can use something like ship finder to see where you are and what time you might get in so people are leaving the transmit on all the time. Have to say though it's less on an issue in the SW.

Why on earth would you call up a ship? Thats why the col regs were written isnt it? The OOW on the ship knows what to do and presumably so do you - also remembering that AIS should NEVER be used as the sole source of information for collison avoidance. The CPA information its giving you is based on the assumptions that both the target vessel and your own GPS, speed log and gyro compass are all performing accurately.

 

[Cardo]

The CPA information its giving you is based on the assumptions that both the target vessel and your own GPS, speed log and gyro compass are all performing accurately.

I don't know about others, but all the data my transceiver uses comes purely from its own dedicated GPS antenna. It's a standalone unit and won't even allow me to share the data from the dedicated antenna with other devices.

 

[PaulGooch]

hi from pacific. The “unreliability" seems likely in more crowded waters like er well, in English channel, frinstance. In emptier offshore sea and ocean there are two sorts of things in the sea - unmarked things like fish and lumps of wood, and marked things like big steel ships. With an ais transponder you are in the second group, without it you are in the first.

I would like to know from a tech person the tech difference between ais A and B - stronger signal or what? I thin either for this boat (or another) I might/would get AIS A

I currently have AIS B and C so my C receiver can watch the the B transponder creep along behind us which is sortof interesting, ish...

Not sure what you're thinking of here, but AIS is broadcast on channel A or channel B, there is no difference between these channels, other than the frequency.

Then there is Class A and Class B. Broadly speaking Class A is for commercial vessels and transmits at 12W, whilst Class B is for leisure use and transmits at 2W.

Not sure what you are referring to with AIS C ?

 

[webcraft]

Why on earth would you call up a ship? Thats why the col regs were written isnt it? The OOW on the ship knows what to do

erm . . . this asumes that the ship has seen you, either visually or on radar or on AIS or a combination of these.

I have called up a ship at a distance of half a mile because I thought they had not seen us. I was right; the OOW did see us when he looked out of the window while talking to me, but had not seen us on radar in the 4m swell. He appreciated my call and warned us about another ship on the same track a few miles behind that we could expect a close encounter with. This enabled me to call this second ship up by name when we sighted her. She was also grateful for the call as she had not seen us either.

The OOW does not have a clue what to do about targets he cannot see, except of course assume that they are not there . . . . you should never assume that a ship is aware of your existence, though an AIS transponder greatly increases the probability that it has.

People who leave their AIS transponder on in crowded inshore waters where the screen is a mass of targets, or in marinas, should ask themselves what exactly they think they are achieving.

- W