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AIS ... again


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OK so why is some AIS illegal in NZ and some not?

 

How can you tell which is which?

 

What's the most likely biggest danger in using one, driving into ship or getting a shitty letter from a little grey man in a polyester suit?

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The issue is the nature of the AIS system. Basically, the standards outline how the units should "share" the allocated frequencies. They should "listen" for a quiet period before transmitting. This is known in the IT world as time division multiplexing. It is critical that ALL units in the area behave as the standards define - If you have a unit that does not behave as the standards outline, it is possible for one unit to disrupt the entire AIS system within range of the faulty/non compliant system. This is a serious issue, not just theoretical! 

 

So, how can you tell? The supplier/manufacturer should be asked to supply a compliance certificate. Make sure that the certificate lists the correct make and model, and at least one of these standards (some are FCC - USA, some are European. I have been given "certificates" for different model numbers, and the wrong standards from Asian manufacturers trying to bypass the (expensive) certifications.

 

IEC 62287, IEC 60945, IEC 61108, IEC 61162, ITU-R M.1371, ITU-R M.825, ITU-R M.1084

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Oh, the biggest danger. Depends, a BIG fine from Radio Frequency Services, and/or hitting something you should have seen, but did not because your unit was jamming both your signal AND theirs, as it had not closed it's transmission correctly... :-( that is worst case of course! 

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Damn right Grant, a dodgy unit is a detriment to everyone. To be completely up front, it is very unlikely that you would get one that actually worked, that is not compliant. However, you never know - who would have thought to put melamine in milk? The certification process it to try to prevent this happening. Honest, reliable companies know they must be certified....

Unfortunately I make the very lowest margin from the Vesper Marine units, so feel free to buy from anywhere. The USA dealers get better buy prices than I do. Doing myself out of business again  :roll: !

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Ah ha, now you say that I do remember seeing a description of how AIS worked and there was limited space, hence that multiplexing thing you mention.

 

I know what you mean about dodgy asian paperwork, you want to see what some do with Certs (supposedly) on our type gear. Rampant dodginess and some is being used in NZ as I write..... by people who do know better.

 

 

Unfortunately I make the very lowest margin from the Vesper Marine units, so feel free to buy from anywhere. The USA dealers get better buy prices than I do. Doing myself out of business again  :roll: !

I know that well as well. The funny thing is I've been buying motorbike and boat bits lately and I'm finding most has been cheaper in NZ than it is buying offshore. I think some just think it's cheaper to shop offshore so don't even bother sussing locally. So I've adopted a ask the locals what they can do, including what can I do to help them possibly do better, before heading offshore. Most are more than happy to be asked and most are happy to work with me to find a way to make it work for both of us. It works. I have got a few bits from offshore but 99% of those things aren't available in NZ.

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There are some AIS units that have fixed allocation time slots - (FATDMA) so if you buy one and it says it transmits in FATDMA mode then it should only be used as an ATON transmitter - and MNZ needs to approve them.

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Having been looking hard at the options in recent days it is a minefield of information. One has to read the fine print of whether they are just receivers, or are actually sending out your position as well. Not always obvious at first glance. Yes the true send and receive units are still not cheap.

 

If you were stuck on a sea anchor in a storm, having your position beamed out to all around you would be a very good thing...

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Tim, if it says AIS class B, or Transponder, it should transmit as well as receive. As you say though, read the fine print! Most that by receivers only are now getting them in a VHF radio. To me a receiver seems to do only 1/2 the job!

 

Here is a basic outline of current pricing - ALL Transponders, Class B;

 

$500= Asian Unit, WITH CE certifications (but not -yet- FCC) NMEA0183 only.

$900=B&G/Simrad/Lowrance + $250 for GPS antenna. NMEA 0183 and NMEA 2000

$1185=Vesper Marine XB8000, WITH GPS antenna, NMEA0183,NMEA2000,USB, AND Wifi, apps for Andriod and apple, provides some conversion for NMEA 0183/2000 as well, and more coming. This is the best non-screen unit currently on the market.

 

The the units with screens, starting with greyscale screens and going up to the Vesper Watchmate vision color unit at $1859.00

 

Other brands are similar prices. IMO you cannot beat the Vesper Marine units for function, support, and quality.

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Can you get just a simple little transmitter that quietly sits in a dark corner banging out your details?

I'm not fussed about seeing what's out there but at times I'd like to make it known I'm out there.

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Doh, brain fart alert. Of course the unit needs to see a GPS or it doesn't know what to tell people.

 

What sort of power consumption do you think is a safe number to work on IT?

Just doing all of that, close as, to make sure what I think I need to generate is enough.

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The units have internal GPS units normally. Just an antenna is external on most models. Power use on most models averages about 4w.  Not much power, and a great backup for your primary GPS unit!

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