AIS class B transceiver

jecuk

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I have just fitted a class B unit both for receive and possible assistance that I can get from the broadcast side. I accept it may not be perfect but who knows - it might help a merchant ship see me even if late in the day.
 

Channel Ribs

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I have just fitted a class B unit both for receive and possible assistance that I can get from the broadcast side. I accept it may not be perfect but who knows - it might help a merchant ship see me even if late in the day.

It is a fair point that AIS is not always used as an alert on big vessel's bridges, but what it is used for is identifying other vessels.

If they do spot a yacht and want more info, then they know just where to get it. Which has to be a good thing.

Three years on and we have still not fitted it to any of our boats, as I said back then there are other things above it on the list.
 

PeterR

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I agree power drain is not a major issue but the average transceiver uses about 0.5 Amps in transmit mode and 0.2 Amps in receive only mode.

More to the point a friend of mine is a Thames pilot so he sees the bridges of more big ships than most and he confirms that only a minority of ships have their AIS receiver linked to their Radar/Nav screens. For most it is a minimum keyboard device at the back of the bridge which they consult only when they want the MMSI of a target they have aquired on radar.

If you can afford both an AIS transceiver and a radar transponder fine. However, if its a question of one or the other why spend money on a transceiver you know will only be seen by a minority of ships when you could spend less on a radar transponder that will will be seen by the majority?
 

boatmike

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who was talking about narrow waters - not me - and yes I would hazard a guess that 14 years of watchkeeping at sea all round the world would probably give me some knowledge.

Yes Mark but those who have been twice around the IoW know much more than you do and object to you disagreeing with them!
Since I crossed the channel with you a couple of years back I am confident in your judgement at sea and in this case (not always, that's asking too much!) I agree with you entirely. My philosophy on a boat is much the same as in a car. Defensive. I am sure some merchant ships are well manned but bloody sure some aren't too! AIS B is the latest whizz bang. It relies on many assumptions that are not particularly well founded and I too prefer to know where others are and what they are doing well in advance to take appropriate action rather than broadcasting "this is me and I have right of way" In fact I have always thought that was an ideal tombstone inscription. I have fitted an AIS receiver and interfaced with the chartplotter it's a great aid. To tell others where I am, I am considering fitting a Seame whotsit which I would think far more useful than AIS B at this time....
 

Channel Ribs

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Lets do a side by side comparison then....

AIS B:

Cost - c420 including backup VHF antenna.

Alerts you of other vessels' locations of certain navigation marks. Does not necessarily alert other vessels of your presence, but does convey information should they choose to look you up.

Also tells (smaller) port authorities and rescue services who you are.

X RTE:

Cost c360.

Alerts you of other vessel's presence, but not location. Alerts other vessels of your presence and location, but does not impart much information other than perhaps that you are a small craft.


In summary then, there is little to choose in terms of cost. One works well if you want to broadcast your presence and the other works well if you want to broadcast more detailed information as well as receiving similar back.

For me this is a difficult trade off, the waters are quite crowded with commercial stuff but fog is also a regular challenge. Since the greatest hazard with either is being run down by something large that did not see you... and the best way to avoid that is to be aware of them and get out of their way then I think AIS B has the edge.

I for one am not content to sit in my boat sending out a big strong PING safe in the assumption that "they" will go around me. Likewise being in fog and knowing that there is something big out there somewhere is not 100% reassuring.
 
T

timbartlett

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My philosophy on a boat is much the same as in a car.
So you don't bother switching your lights on because so long as you can see other vehicles, there is no need for them to see you?
I am sure some merchant ships are well manned but bloody sure some aren't too! AIS B is the latest whizz bang.
One of the most fundamental of the colregs is the one that requires all vessels to keep a proper lookout by all available means. For a ship's watchkeeper to arbitrarily choose to ignore his AIS just because it's "one o' they 'lectronickery things" is unprofessional -- criminal, even. I don't disagree that some do -- but AIS has been around for a good few years now: bridge displays are getting better, and watchkeepers are gradually getting used to it. A growing proportion of watchkeepers will never have been to sea without it: for them, it is as much a part of standard bridge equipment as radar.
It relies on many assumptions that are not particularly well founded
At least it doesn't rely on smoke and mirrors like radar reflectors! AIS B does work. Radar reflectors do not. Even the MAIB, after the Ouzo collision, failed to find a single commercially-available radar reflector that met the basic minimum performance standards.
rather than broadcasting "this is me and I have right of way" In fact I have always thought that was an ideal tombstone inscription.
There is no such thing as "right of way" at sea. Telling people "I am here" is not the same thing at all.
 

rob2

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One of the issues in the Ouzo enquiry was that the look out was spending more time patrolling the ship than standing watch and therefore had reduced night vision. There was also no attention being paid to the x-band radar, they were principally watching commercial traffic 20 miles away on s-band. No-one here should be making inferences about each others' practices, but the enquiry threw up a picture of a lax regime on the bridge of a commercial ferry!

Rob.
 

boatmike

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It's what I implied certainly Malthouse. There are situations where you are theoretically the stand on vessel and it is wrong to change course too late if you are creating an "after you Cecil" situation by doing so. Early action to avoid a close quarters situation with very much larger vessels is what I mean by "defensive driving" though and this applies on the road as well of at sea. The contention that I suggested "driving without lights" is a distortion and deliberately argumentative (by timbartlett not you) in my view, as I did say I was considering a SeaMe transponder which I consider is probably more effective in telling others where you are. Your price comparison is interesting as a value for money argument. Indeed value for money is important because without cost as a consideration we would probably all have everything. My own opinion though is that AIS receiver only options are cheap and the best use of money for the average yottie who believes in defence. In terms of transmitting ones own position, while radar reflectors do in fact work they are far less effective than SeaMe. My choice would therefore be (and is) AIS receiver only plus SeaMe. No one device does everything and its an individual choice what you invest in, but the original point that Talbot made was that it's far better to have really good information yourself to know how to aviod trouble than to rely on others seeing you.
 

Channel Ribs

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My choice would therefore be (and is) AIS receiver only plus SeaMe. No one device does everything and its an individual choice what you invest in, but the original point that Talbot made was that it's far better to have really good information yourself to know how to aviod trouble than to rely on others seeing you.

That makes a great deal of sense. :)

I think in my local waters (Channel Islands) where radar coverage is sparse but 20nm is enough range to have my boat pop up on lots of screens at any given time, then the Transponder is still the best.

There was an excellent discussion on RIB.net a few weeks ago, basically everyone came to the conclusion as the H.M. linked to above: It all depends on what your cruising grounds are like.
 

mobeydick

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Lets do a side by side comparison then....

AIS B:

Cost - c420 including backup VHF antenna.

You always seem to need an NMEA mux to interface to your plotter, which is another £100+ on top.

On another issue, would a timer on the 'transmit' function be an idea on class B Units? So e.g. it only transmits for an hour or so after pressing a button, to stop overwhelming numbers of tracks.

MD
 

jecuk

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You always seem to need an NMEA mux to interface to your plotter, which is another £100+ on top.

On another issue, would a timer on the 'transmit' function be an idea on class B Units? So e.g. it only transmits for an hour or so after pressing a button, to stop overwhelming numbers of tracks.

MD

Most now have NMEA out which goes straight into NMEA in on the plotter. Most class B's I think have an on and off button so you can stop broadcasting when there is no need.
 

mobeydick

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Most now have NMEA out which goes straight into NMEA in on the plotter. Most class B's I think have an on and off button so you can stop broadcasting when there is no need.

No, they output at a high speed, so you need to mux in any lower speed devices.

'Can' stop, but wouldn't.

MD
 

Colvic Watson

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Should Trading Standards prosecute the makers and marketers of class B transceivers? 1 or 2 percent of ships will see you on a plotter type screen, the rest will have your lat & long in text format displayed on a three line LCD display at the back of the bridge. And they'll all turn off class B signals in waters frequented by yachts.

This sumer we sailed from the Deben to Titchmarsh; we crossed the busy Harwich entrance so had the CPA alarm on for our AIS on the plotter screen. But some berk in a yacht was sending out class B signals whilst he was happily tacking and sailing around having fun. Good for him, except every 10 minutes or so as he tacked our CPA alarm went off because his projected course was crossing ours. So we turned off the CPA alarm. Anyone care to guess how many of those 1 or 2 percent of ships that can display AIS on a plotter screen had long ago turned off class B signals? I wish we could have done, anyone know of a software patch to do this on NASA units?
 

mobeydick

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Exactly. Class B transmit should be like car fog lights. Default is OFF and you only switch on when you need it. (with timer to turn off again)

MD
 
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