Type "A" AIS for Yachts?

[David M]

I use a Class A type AIS (Furuno FA150). It's not a hassle to use.

[sgtPluck]

I can only speak about type B, but have found it to be a very useful tool and I don't see much need for me in 'upgrading' to A.
My system cost very little as it came built-in with my Standard Horizon radio, (around $300) and it sends the data to my chartplotter as well as having a display on the VHF.
In practice I've set the alarm on the VHF itself, and found it is more than adequate at picking up shipping from a safe distance and alerting me. You can also initiate a DSC call to a target on the VHF, which they might be more likely to respond to than hailing on 16. But even just having the name of the vessel to hail on 16 has been in my personal experience been the difference between getting a response or being ignored.

[David M]

Originally Posted by sgtPluck

I can only speak about type B, but have found it to be a very useful tool and I don't see much need for me in 'upgrading' to A.
My system cost very little as it came built-in with my Standard Horizon radio, (around $300) and it sends the data to my chartplotter as well as having a display on the VHF.
In practice I've set the alarm on the VHF itself, and found it is more than adequate at picking up shipping from a safe distance and alerting me. You can also initiate a DSC call to a target on the VHF, which they might be more likely to respond to than hailing on 16. But even just having the name of the vessel to hail on 16 has been in my personal experience been the difference between getting a response or being ignored.

For hailing commercial vessel try 13 first.

[Paul Elliott]

We should probably clarify the differences between AIS "A", "B", and receive-only units.

Class-A transponders transmit at 12W, send more information, send it more often, and have a higher priority when the AIS radio channels become crowded. Class-A is mandated on larger vessels, and voluntary on smaller ones. Class-A transponders are more expensive and consume somewhat more power.

Class-B transponders transmit at 2W, send less detailed information about your boat, and send it less often. Class-B is voluntary. It is less expensive than Class-A, and consumes less power (my ACR Class-B transponder draws about 0.3A @ 12V).

Receive-only has somehow been popularly referred to as "Class-B". I've seen this usage in several magazine articles, but this is not the proper term. For example, the Standard Horizon "Matrix" series of VHF radios may include an AIS receiver. This is "receive-only", not "Class-B".

Receive-only is the least expensive, and lowest-power system. Other than a few obsolete receivers (such as the original NASA receiver), receive-only units will receive and decode both Class-A and Class-B signals.

There are single-channel and dual-channel receivers. Since the AIS transponders alternate their transmissions between two VHF channels, the dual-channel receivers will more quickly pick up the less-often sent vessel "static" data (name, callsign, status, dimensions, cargo, etc). The single-channel receivers are less expensive and still work reasonably well for collision-avoidance.

Anyway, I am happy with my Class-B transponder. I am usually seen by other vessels at or beyond visual range, and I can see other Class-B equipped boats at similar ranges. I do not believe that Class-B "filtering" is common -- it's not really an issue.

Class-A does have some messaging capability that is lacking in Class-B, but this feature is seldom used and I don't think it is much of a benefit.

One very nice feature of the Standard Horizon (and some other integrated units) is that they enable easy VHF DSC calling, using the vessel information received via AIS.

[Dockhead]

Originally Posted by estarzinger

It sounds like you understand and are fine with the major potential drawbacks, and value the potential benefits of A.

Personally I am the opposite. I think B works very well and I don't see much extra value in the 'benefits' of A, while I don't want the drawbacks.

Drawbacks: the extra cost, power consumption, and need to fill out extra data fields.

Benefits: slightly longer range than B - but not as much as you think and honestly the range of B is more than satisfactory, a possibility in very crowded waters that your signal will find a slot when a B does not, a possibility that ships will take your signal more seriously - but probably not all that an big effect.

Very logical and persuasive. I might go with Class "B" yet.

[nigel1]

Originally Posted by Dockhead

I talked to some commercial mariners about this. They say that most of their AIS sets don't have a specific filter for Class "B" signals, but they can set filters for size and speed, and that they do filter small and slow targets in very crowded conditions, besides filtering out targets with more than x CPA. I can well imagine that in the Solent, for example, where there can be thousands of boats out, and a large commercial vessel simply cannot track all of the possible targets. Besides that, Class "B" signals will get kicked off the system if the

Dockhead,
Sitting in front of me is an innocuous Furuno UAIS FA-150 Transponder,. The display is about 3 inch, and its crap to use, but its the heart of the ships AIS system. It is intergrated to two 27 inch ECDIS displays and two 27 inch radar displays.
No where on the Furuno 150 AIS is there any function to filter out any target. The only option is to set a CPA and TCPA, and if the alarm is set to sound, it will sound when a target meets the TCPA and CPA alarm.

Filtering is carried out on the ECDIS and the Radars. I cannot speak for other commercial mariners, but there is no way that I can filter out a target based on size and speed. Both the ECDIS and Radars have a tick box in the AIS setup window "Filter Class B". That's all we can filter.
Even then, the CLass B target will be a "sleeping target", will have a small icon. If that sleeping target encroaches the CPA and TCPA limits set on the ECDIS and Radar, then it becomes active.
One really annoying thing I have found about AIS in my job, I like the OOW's to have the AIS TCPA/CPA alarm set, and thats really annoying when the thing I'm towing, or another tug on the same tow has AIS, and we have found that there is no way we can filter them out, even the manufacturers of the system tell me it cannot be done. So I'm not sure if its at all possible to filter based on size and speed.'

In answer to the original question, I'd go for Class B and spend the rest on something really useful.

[noelex 77]

Originally Posted by nigel1

In answer to the original question, I'd go for Class B and spend the rest on something really useful.

Something like this looks like it could make a very positive contribution to safety.
A personal AIS MOB beacon.

SafeLink R10

[Thumbs Up]

Harbor with my class B AIS. Very helpful. The commercial guys can see me and I can see them. Had no surprises of them creeping up from behind.

I too am considering buying a transponder (class A). The commercial boats CAN NOT see you with the class B AIS. You can see their info but they cannot see yours! My friend reported that with his transponder, if a ship was in his vicinity they never failed to contact him on VHF. With a Class B, you can see them, who they are, their course etc. but they still can't see you!

[noelex 77]

Originally Posted by Thumbs Up

I too am considering buying a transponder (class A). The commercial boats CAN NOT see you with the class B AIS. You can see their info but they cannot see yours! My friend reported that with his transponder, if a ship was in his vicinity they never failed to contact him on VHF. With a Class B, you can see them, who they are, their course etc. but they still can't see you!

There are both class A and class B transponders. I may be misunderstanding your post, but I think you talking about the differences between class B receivers and Class B transponders.
The technology is moving quickly.

A couple of years ago most cruising yachts were fitting class B receivers. Now class B transponders are the most popular option (and the one I will probably fit), but class A transponders for yachts are now becoming an intriguing option.

[Thumbs Up]

OK, I see, my mixup. Class B's are also transponders, I was confusing them with receive only. Anyway, the fact that all commercial vessels worldwide are required to have AIS makes this the most important tool for avoiding collisions that we have. We should all get AIS!

[ranger58sb]

Originally Posted by Thumbs Up

I too am considering buying a transponder (class A). The commercial boats CAN NOT see you with the class B AIS. You can see their info but they cannot see yours! My friend reported that with his transponder, if a ship was in his vicinity they never failed to contact him on VHF. With a Class B, you can see them, who they are, their course etc. but they still can't see you!

We have a Furuno FA-50 Class B transceiver installed, and I've had commercial ships call me.

-Chris

[jeremiason]

Originally Posted by sgtPluck

I can only speak about type B, but have found it to be a very useful tool and I don't see much need for me in 'upgrading' to A.
My system cost very little as it came built-in with my Standard Horizon radio, (around $300) and it sends the data to my chartplotter as well as having a display on the VHF.
In practice I've set the alarm on the VHF itself, and found it is more than adequate at picking up shipping from a safe distance and alerting me. You can also initiate a DSC call to a target on the VHF, which they might be more likely to respond to than hailing on 16. But even just having the name of the vessel to hail on 16 has been in my personal experience been the difference between getting a response or being ignored.

International Radio Laws require a vessel equipped with GMDSS (DSC for the big guys) have either a radio officer or a passive alarm indicating that they are receiving a DSC call. Since most commercial ships are now required to have GMDSS, they may not be monitoring Channel 16 by listening, instead using the DSC alarm.

Also in areas controlled by a Vessel Traffic Service, most commercial vesels will be monitoring VTS and Channel 13, instead of Channel 16.

People made this mistake all the time in San Francisco Bay, trying to hail commercial traffic that wasn't listening to Channel 16.

As far as the OP's question....

I used Class A AIS units in San Francisco on a number of commercial vessels I captained. They are great unit, but display more information than you need for a recreational vessel and require manual imput.

So if you you think you can afford it; Think you need to know things like rudder turning angel, ship dimensions, GPS anntenna location on the vessel; and finally don't mind everytime you move to have look up the maritime code to manually imput your destination into the AIS so you can tell everyone where you are going... Then buy it.

My advice is stick with the Class B and use the additional money for other toys

[nigel1]

Originally Posted by noelex 77

Something like this looks like it could make a very positive contribution to safety.
A personal AIS MOB beacon.

SafeLink R10

Have two similar units on the tug, purchased after one of the crew got his foot fouled in an anchor buoy rope and was dragged over the stern. This was in the Baltic in January with vis down to about 50 meters.

Not had to use them in anger, but tested often from the rescue boat. When activated, we can pick up the signal from about 3 miles, and will sound an alarm on the AIS/Radar and ECDIS, with the Distress AIS clearly indicated. Found that the position does jump around abit, but its close enough to get back to someone in the water

[noelex 77]

Originally Posted by ranger42c

We have a Furuno FA-50 Class B transceiver installed, and I've had commercial ships call me.

-Chris

I have not yet fitted AIS, but in talking to other cruising boats it seems one of the major advantages of AIS is calling a ship by name.
Away from English speaking countries the number of ships that will answer a VHF hail, without a ship name, seems close to zero.
The last response I had to to VHF call was from a warship over 12 months ago and that was only because they wanted to speak to me. (The military jet that flew at masthead height and scared the bejesus out of me at 2am was the clue)

[barnakiel]

I think A is great. I can see A units from at least twice the distance!

If I were buying an active unit (and if we could afford A which I believe are pretty expensive) I would buy one.

b.