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Old 20-07-2020, 10:58   #1
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AIS only showing class A names

My AIS transponder, Raymarine 500, is only showing names of class A vessels on the B&G Zeus2 12 inch. Class B vessels are shown but only the MMSI numbers, not name, length etc. This a a very crowded area with lots of both class A and B vessels. The Transponder and plotter are connected via a combination of Raymarine NG and Micro C N2K. Anyone experienced the same and hopefully found a solution?
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Old 20-07-2020, 11:18   #2
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Re: AIS only showing class A names

How long has the system been running ... the static information (name etc) is only sent every 6 minutes, so if you miss one you will have to wait a while before it gets sent again.

There's a couple of reasons I can think of that you might be missing the class B signals ...

There is limited bandwidth to the AIS system, so in a very crowded area, class A signals get priority, making it harder for class B signals to get through. There is nothing to stop class B units "fighting" for the same transmission timeslot, so in a very busy area they may be interfering with each other. Class B signals operate in the gaps left behind by the class A signals, but if a class B unit isn't receiving distant class A signals that you are receiving, then it may try to transmit at the same time thinking that there is a gap there.

The new class B+ units solve most of these problems ... but as long as you are receiving the position reports, then you've got what is most important ... but remember that in crowded conditions, although these are updated every 30 seconds, these too could be minutes old.


Edit: another possibility ... if the Plotter has limited memory for storing ships names, in a crowded area, it may prioritise the class A data when it runs out of memory.
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Old 20-07-2020, 12:47   #3
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Re: AIS only showing class A names

Thank you, I am aware of the limitations of class B, the system has been running for several hours. Not a single class B target is showing names etc. Class A looks flawless however. The Zeus 2 is a rather recent plotter which should have plenty memory available I would assume, my old Raymarine E120 suffered from this issue before a SW update was released, this was several years ago. It might be a N2K problem but I donít know how to check...
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Old 20-07-2020, 13:46   #4
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Re: AIS only showing class A names

Curious ... You are getting plenty of AIS messages to the plotter via N2K, so it's not a hardware problem in the N2K network ... the network is working.

I have a zeus2 and AIS receiver using NMEA0183, and it works fine. So once the AIS messages are decoded the plotter should handle them correctly. If you can connect via 0183 and it works, then there may be a software problem with AIS message #24 (class B names) not being properly handled by the N2K encoding/decoding. If the problem persists using 0183, then it is unlikely to be an N2K issue.
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The Zeus 2 is a rather recent plotter which should have plenty memory available I would assume
You would hope so, but you know what they say about assumptions.


good luck.
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Old 21-07-2020, 09:27   #5
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Re: AIS only showing class A names

Quote:
Originally Posted by STAYER View Post
My AIS transponder, Raymarine 500, is only showing names of class A vessels on the B&G Zeus2 12 inch. Class B vessels are shown but only the MMSI numbers, not name, length etc. This a a very crowded area with lots of both class A and B vessels. The Transponder and plotter are connected via a combination of Raymarine NG and Micro C N2K. Anyone experienced the same and hopefully found a solution?

Yes, I saw that but only in a place where there were a huge number of class A around, in fact it was in the Panama Canal area and I don't think it happened anywhere else.

I suspect there is a memory limitation in the receiver, probably not in the Zeus MFD. My AIS receiver is a SH GX2002 VHF unit that feeds into a Zeus Touch 12".
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Old 21-07-2020, 18:09   #6
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Re: AIS only showing class A names

I only sail in the Pacific & SE Asia, so I canít say anything about where u are. I have a top of the line Vesper XB8000 and many times it only shows the position data, CPA, etc and MMSI number. Doesnít matter if itís crowded or only 1 vessel. Maybe not all ships are set up to show names? It doesnít really matter to me as long as I have the navigation data. Here in SE Asia tugboats are the worst: NO AIS, not standard lights & no lights on tow. Go with the flow! Evan on JAVA
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Old 21-07-2020, 19:08   #7
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Re: AIS only showing class A names

No lights on the tow......yikes barbaric
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Old 02-08-2020, 13:25   #8
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Re: AIS only showing class A names

After quite a bit of research the net result is that the Raymarine AIS 500 has a limited memory capacity. I changed it for an AIS 700 and all works fine.
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Old 02-08-2020, 14:50   #9
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Re: AIS only showing class A names

I don’t know the unit. Does it have filters? Filtering may free space.
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