AIS - Can I Recieve Permanently but Choose to Switch On / Off Transmitting ?

[goboatingnow]

Contary to popular internet myth big ships can NOT filter out class b ais. There are some issues with static data on class b put the basic info is there. Ships state
Can set active/ inactive ranges etc but not " filter out" anything

Dave

[Jon Hacking]

Originally Posted by SoggyPaws

So HAS anyone actually bought and used the AMEC Camino-101?? Thinking about making a purchase in the next month and wondering what we're not getting with that unit that we get from other similar (Class B, no display) units.

OK, here are our initial reactions to playing with the Camino-101 Class B AIS.

Overall impression: It’s a nice piece of kit. It seems to do what it’s supposed to, quietly & efficiently. Thumbs up!

The good: We bought ours from Milltech Marine for $495. Doug was very helpful. Installation was straightforward. It’s several times bigger than my old SR161 AIS receiver (2x footprint, 2-3x as high) but it fit in the same space. It comes with all cabling you’ll need, even a 4’ serial cable as well as a separate NMEA cable (which we don’t use - we plug all serial/NMEA devices into a KeySpan 4-port serial/USB converter). It uses a proper PL239 VHF connector instead of the BNC on my SR161. It draws almost no power so we just leave it on. It only transmits a burst every 3 minutes if we’re moving at less than 2 knots, so most of the time it’s just a receiver. Changing the baud rate & the GPS antenna location was easy with the included Configuration program. We haven’t used the included AIS Viewer program much as we want to use the AIS with our navigation programs (MaxSea & OpenCPN). It works well with both nav-programs once we turned the baud rate down to 38.4. The viewer seems to have a concept of “friendly” boats, which presumably are ones that the Viewer doesn’t worry about.

The bad: A friend’s different class B AIS picked up ships a bit further away than my Camino-101. OK, his antenna is 30’ high & mine is only 10’ high. That may be the whole issue but I can’t tell. My Camino seems pretty good out to maybe 40 miles, which seems sensitive enough to me, & I often pick up ships much further away (but there are AIS repeaters here so it's difficult for me to judge receiver sensitivity). Also, the software switch to turn off the transmitter (making it just a receiver) is in the Viewer program, not the Config program. This switch (& some others?) are also not documented in the manual, which seems to refer to an earlier incarnation of both the Viewer & the Config programs. OK, I don’t intend to use either program much. Finally, getting called by Brunei Port Control while we were still a few miles away (& planning to wait until tomorrow morning to clear in) made me realize that we’re always visible to the authorities now.

The ugly: The Configuration program is apparently not written for Vista or Win7 (although I ran it under Win7 & it did what I needed to do). It runs OK but when shutting the Config program down, it wants to save some information in an INI file, where the program is stored. Microsoft has said this is a no-no, that only the OS can change the Program Files folders, & that this sort of info should be placed in a mirror folder under C:\ProgramData. So you try to shut the Config program down, it tries to write the INI file, fails, puts up a dialog box saying it failed - & doesn’t shut down! You have to either run it as Supervisor or nuke the program with Task Manager. Again, I probably won’t need to run the Config program ever again so it’s not that big a deal.

[David M]

Originally Posted by impi

I cannot seem to get any clear answers to this question, and was wondering if there was an AIS unit that gives one the flexibilty of choosing to switch off transmission of signal whilst still recieving? (eg. in waters where hostile craft are - would like to recieve AIS but not transmit my signal)

Yes, the Furuno FA-150 AIS transceiver can do this. I have one onboard.

You can call Furuno at 888 834-9330 to confirm this. Ask for tech support.

[SoggyPaws]

Jon, thanks very much for your thoughtful review.

On disabling transmit mode: Some transceivers have a hardware switch on the outside of the box that will disable transmit. Others have a software switch that you need to run a configuration program for. I am not positive, but I think all of them have a way to stop transmitting while still receiving--and more likely this capability will be in a newer unit than an older one.

I THINK there is actually a capability in the specs for Port Control in a harbor to be able to turn off transmit by broadcasting a code--maybe only for Class B? (not sure where I read this, so don't quote me on this part).

MilltechMarine.com has user's guides and stuff for the units they sell, checking the guide (or email Milltech) would be the best way to confirm for a particular unit.

[goboatingnow]

I THINK there is actually a capability in the specs for Port Control in a harbor to be able to turn off transmit by broadcasting a code--maybe only for Class B? (not sure where I read this, so don't quote me on this par

NO they cant, they can switch channels , control slot priority etc to ensure that close in ships get priority etc, but the specification does not allow ANYONE to supress AIS transmission, except the ship itself.

IN the early days of Class B myths where progagated that CLass B data could be suppressed on turned off by ships etc, nothiong could be further from the thruth.
Dave

[SoggyPaws]

Thanks for the correction (I should have looked this up before I posted)!