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Old 02-22-2015, 01:03 PM   #21
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I don't get it either. My screen has never been crowded, nor cluttered up as some have described it.

And, I'm not just worried about the big boys when its foggy.

Also, a couple of months ago someone here also complained that some boats leave their AIS's on when tied up at marinas. Really? That's a problem somehow? Seems like complaining just to complain.
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Old 02-22-2015, 01:05 PM   #22
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Me 3. We live in the yachting capital of the world, and it doesn't crowd my plotter. Ok maybe if I'm zoomed out looking at the the whole southern part of FL but if I'm that zoomed out I'm not using it for navigation anyways.
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Old 02-22-2015, 05:34 PM   #23
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It's good to know what the big ones are doing so we have an AIS receiver on board. But we don't have a transceiver since the big ones might suppress class B signals especially in those situations where I would like that they see me.
Therefore we consider AIS just as a contribution to our "active safety" rather than to "passive safety". We will never rely on the thought: "the big one has seen our tiny boat" - we will try to talk with him in any case of necessity.
That's it what AIS is helpful for us: to get name / call sign / MMSI of those big ones whose CPA seems a little bit too close (but AIS will not substitute RADAR in our opinion).
And if the big one is not answering our call and continues to come close we will go on the run ...



best regards / med venlig hilsen
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Old 02-22-2015, 05:36 PM   #24
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Quote:
Originally Posted by waddenkruiser View Post
It's good to know what the big ones are doing so we have an AIS receiver on board. But we don't have a transceiver since the big ones might suppress class B signals especially in those situations where I would like that they see me.
Therefore we consider AIS just as a contribution to our "active safety" rather than to "passive safety". We will never rely on the thought: "the big one has seen our tiny boat" - we will try to talk with him in any case of necessity.
That's it what AIS is helpful for us: to get name / call sign / MMSI of those big ones whose CPA seems a little bit too close (but AIS will not substitute RADAR in our opinion).
And if the big one is not answering our call and continues to come close we will go on the run ...



best regards / med venlig hilsen
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Old 02-22-2015, 05:38 PM   #25
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Old 02-22-2015, 06:06 PM   #26
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But in the past 6 months I discovered that Pugent Sound and Seattle VTS does not receive Class B AIS, only Class A.
Do you know if this is true of all USCG VTS stations?

Now that I think of it, Al (FlyWright) is leading a group on a tour of the San Francisco VTS Center sometime soon. Hey Al, if you're reading this, can you ask them while you're there if they only monitor Class A AIS? And, if so, why?
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Old 02-22-2015, 06:12 PM   #27
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I have a class B transceiver. Love it and do rely on it just as I do radar. All shows up on my Garmin 7210 system.. I have had several communications from barges here in mobile bay or the rivers and they are glad we are sending as well for their own knowledge. It's simply not that much more cost wise to have both sending and receiving capability.
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Old 02-22-2015, 06:47 PM   #28
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And, what about Canadian VTS - do they monitor both Class A and Class B?
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Old 02-22-2015, 07:27 PM   #29
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Do you know if this is true of all USCG VTS stations?

Now that I think of it, Al (FlyWright) is leading a group on a tour of the San Francisco VTS Center sometime soon. Hey Al, if you're reading this, can you ask them while you're there if they only monitor Class A AIS? And, if so, why?
No, I don't think it is universal, in fact I think Puget Sound and Seattle may be outliers. I think the only other place I have engaged VTS has been going through the Cape Cod Canal. I didn't have to check in, but at one point they called me by name, presumably from my Class B AIS.

I'm not subject to Puget Sound or Seattle VTS either, but checked in anyway on our way in from the ocean since it was zero visibility the whole way. They were happy to hear from us, but couldn't see us on AIS.
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Old 02-22-2015, 10:25 PM   #30
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No, I don't think it is universal, in fact I think Puget Sound and Seattle may be outliers. I think the only other place I have engaged VTS has been going through the Cape Cod Canal. I didn't have to check in, but at one point they called me by name, presumably from my Class B AIS.

I'm not subject to Puget Sound or Seattle VTS either, but checked in anyway on our way in from the ocean since it was zero visibility the whole way. They were happy to hear from us, but couldn't see us on AIS.
Couldn't see you on AIS? But dont you have Class A ?
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Old 02-22-2015, 10:31 PM   #31
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Couldn't see you on AIS? But dont you have Class A ?

He had a Class B, but it came out with all the Simrad gear and was replaced by a Class A unit.
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Old 02-22-2015, 10:32 PM   #32
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Ah, thanks.
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Old 02-23-2015, 06:07 AM   #33
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Hi Oliver,

I've heard the same rumors, but my experiences lead me to believe otherwise. I spent a lot of weekends this summer running into and out of Seattle, which is extremely busy with both commercial and recreational traffic.

I have observed on several occasions when I've been involved with complicated crossing situations that large commercial traffic has altered their course based on my AIS class B transmissions (they could not see me via Radar or visually at the time). One particular situation comes to mind that involved 5 vessels having to give way slightly and a tug with tow that was the stand on vessel for the other five. All six vessels did what they were supposed to like a well choreographed dance. It was impressive to watch.

To the OP, I have a Simrad AIS transceiver, which works well for me. It outputs NMEA 0183 and 2000, so the vessel data shows up on the Navigation PC's, the Furuno gear and the Simrad Chartplotters.

Of course, YMMV,
: thumb:

Exactly my experience.
Also see Kevin's paragraph about working backwards. Decide what you will view it on and go from there.

While I did use Marine Traffic app for two years, I certainly can't see paying for a receiver only set up, when the transceiver only costs $200 more.

My Digital Yacht B class transceiver cost only $580.

On B versus A. I wonder who started the rumor that ships turn off the B?

How does that even make sense? As the little boats who do transmit B are exactly the ones that are hard to see, yet they want to avoid.

In hindsight, unless one spends virtually all their time in the ICW, The ais transceiver should have been one of my first purchases.

My average ship encounter distance went from collision course to greater then 3 nm, and normally greater than 5nm.
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Old 02-23-2015, 07:38 AM   #34
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And, what about Canadian VTS - do they monitor both Class A and Class B?
Yes. In Straits of JDF both US and Canada appear to monitor B, so am curious about Seattle VTS.

Class B has a less frequent transmit cycle than A. B does not give you a real time image like radar. Not uncommon for an 1/8 to 1/4 mile separation if target vessel is moving at 30 knots.

Sometimes sport fishing charter vessels turn off AIS in Alaska as they get paranoid about sharing fishing grounds.
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Old 02-23-2015, 08:04 AM   #35
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Yes. In Straits of JDF both US and Canada appear to monitor B, so am curious about Seattle VTS.
That was not my experience in October 2014. I checked in with JDF VTS and told them where they would see me on AIS. They couldn't see me and asked if I had Class B, which I did at the time. They said they do not receive Class B. This is first hand. I subsequently overhead the same conversation with other boats that had Class B.

Now keep in mind that I'm talking about VTS, not about the various boats out there. I expect they CAN see Class B. I think only pretty old, first-generation AIS devices don't receive both.
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Old 02-23-2015, 08:27 AM   #36
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The Puget Sound VTS, puts out a user guide in PDF.

Juse read through it and it said no "B" tracking....

But just cause it's online...not fact as it may have not been updated or could be in error....could always call if really interested.
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Old 02-23-2015, 09:21 AM   #37
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Finally the thread begins to get it right. Class A and B work exactly the same except class A is refreshed in a way to not miss another transmitting AIS as often as the Class B might. The difference in AIS to most of us Leisure/recreation boaters is whether the AIS is a receiver only or a transceiver. Clearly it is a nice improvement to have a transceiver and let others see you than to only have a receiver that lets you see others but they can't see you. Most Transceivers including mine have a no transmit switch. I can turn my transmitting off, go figure as to why I would want to do that. I say most bang for the buck is a Class B transceiver. I paid $500 for mine at West Marine.
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Old 02-23-2015, 09:35 AM   #38
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Since an AIS that transmits... first transmits whether it is a class A or B, traffic folks that are looking only at commercial traffic can and do often set their receivers to not track class B AIS. This is why you are sometimes warned that class B units are not tracked. It is not because they can't see them its because they are not concerned with them, and are literally not tracking them. If traffic folks set their receivers to not see class B then they can't see them.
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Old 02-23-2015, 10:38 AM   #39
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I'd be real interested to see an example of a receiver that has a "don't receive Class B" switch on it. So far I haven't seen one.

As for VTS in the greater Puget Sound, all I can really say is what my interaction was with them. It was pretty clear that whatever display they were using to see boats did not display Class B devices. For me and a few other boats transiting the area, their words were "we can't see Class B AIS", not something like "oh, I see you are class B, we won't track you". Actually, just the opposite. They did track us and asked us to check in at various points long the way.
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Old 02-23-2015, 10:45 AM   #40
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: thumb: On B versus A. I wonder who started the rumor that ships turn off the B? .
Not necessarily a rumor. Panbo has a very long thread on realities vs myth of Class B filtering by large ships as started by the AIS expert - Norris.

On a side note, Class A has a "refresh" rate of 2 to 10 seconds and class B 30 to 180 seconds dependent upon target distance. So best we keep our radars on and in good working order as Class B AIS is only a good but not perfect tool in snotty weather close encounters.
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