Connecting VHF, AIS, GPS - NMEA0183 and NMEA2000

[jeffrobbins]

Thanks John for answering the question while I was away. Indeed, it responds to certain messages sent to it as well as interrogations originating from other stations so calling it a transponder is correct. It doesn't only transmit your dynamic position and static data as Jon assumed.

Possible little known fact... it also receives remote commands via DSC too. It has a schedule when it knows to check for them on the DSC frequency.

And sorry for the delayed reply as I'm sometimes traveling overseas on business trips and not always able to keep up.

[Jon Hacking]

Thank you John & Jeff. Good to learn something new. Although there's certainly not much documentation on when such queries might occur, or what equipment is able to make such queries. I wonder if one can opt out of such interrogation by turning off Xmit mode.

[jeffrobbins]

Originally Posted by Jon Hacking

Thank you John & Jeff. Good to learn something new. Although there's certainly not much documentation on when such queries might occur, or what equipment is able to make such queries. I wonder if one can opt out of such interrogation by turning off Xmit mode.

The documentation and details are described in the ITU-R M.1371 spec that John referenced.

You cannot opt out other than the switch the AIS off or put it in silent mode (RX only). If you are transmitting AIS then it must respond to queries and remote commands as appropriate. However, I can't see any reason why you would want to opt out. The point of this is to enhance AIS communications and integrity between vessels and shore stations and to protect the VDL. It's kinda like saying I want to have a cell phone but I don't want my phone to obey network control protocols.

[Jon Hacking]

Originally Posted by jeffrobbins

...I can't see any reason why you would want to opt out...

If you're in, say, Puget Sound, then I agree. Everyone needs to see where everyone else is & where they're going. The more the merrier.

But in SE Asia, there are some who don't have my best interests in mind. We leave our AIS on most of the time, including our last 3 transits of the Malacca Straits, but it's not the officials out there that worry me. What can the Mindinao pirates (that have been harassing NE Borneo) see or do with my AIS? Unfortunately, the bad guys ain't always dumb.

[jeffrobbins]

Originally Posted by Jon Hacking

But in SE Asia, there are some who don't have my best interests in mind. We leave our AIS on most of the time, including our last 3 transits of the Malacca Straits, but it's not the officials out there that worry me. What can the Mindinao pirates (that have been harassing NE Borneo) see or do with my AIS? Unfortunately, the bad guys ain't always dumb.

You can always switch your AIS into silent mode if you are in an area of concern. And you don't have to worry too much about what they can do to your AIS remotely though. In order to do anything, they will already know where you are and all they can really do is interfere/restrict/disable your transmissions in various ways.

[Ziggy]

[QUOTE=jeffrobbins;1983391]Sorry Jon, I misunderstood what you were looking for. As far as I know the GX2000 doesn't accept a combined GPS & AIS data stream. At least that's how it used to work and they are at different baud rates. They changed it in their newer radios. Maybe one of the owners can confirm this./QUOTE] I have a GX2000 VHF with a Vesper XB-8000 AIS transponder. The GX2000 receives both AIS and GPS from XB-8000 just fine. It's a great combination.

[Jon Hacking]

Originally Posted by Ziggy

I have a GX2000 VHF with a Vesper XB-8000 AIS transponder. The GX2000 receives both AIS and GPS from XB-8000 just fine. It's a great combination.

Thanks Ziggy! Exactly the info I was looking for. Presumably that's on the same NMEA stream, at 34,800 baud?

Do you have other thoughts (+ or -) on the GX2000 as a VHF?
How is the speaker in the mic?
Can you adjust the AIS alarms?

[Ziggy]

Originally Posted by Jon Hacking

Thanks Ziggy! Exactly the info I was looking for. Presumably that's on the same NMEA stream, at 34,800 baud?

Do you have other thoughts (+ or -) on the GX2000 as a VHF?
How is the speaker in the mic?
Can you adjust the AIS alarms?

I really like the GX2000/XB8000 combo. I use it with a cockpit mounted RAM3 mike, which has an adequate (but not great) speaker and a small LCD display. The only negative is that the AIS filters are fairly crude, so when in a place with a lot of traffic I turn off the alarm, otherwise it goes off nearly continuously. And when the alarm goes off, you have to silence it before you can change modes or channels. Not a problem when there are only a few AIS vessels in the neighborhood.