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Old 21 November 2018, 07:36   #71
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Originally Posted by Xk59D View Post
You called that correctly, nice.

So given I couldn't see part of your trip and it went to 30 min updates there is a coverage gap in that loch, probably both lochs actually? If the receiver is at KIP, as we speculated, that would maybe tie in as you were probably about 10 miles from KIP when you and breeze stopped updating.

Did you show up on it when you were testing it at home?

Next question is how class A gets on there in middle of an ocean.
Satellite. I have a similar setup on our sailing yacht, only using mobile data - when within range of some form of 2G/3G/4G coverage, I can upload AIS positions for us and everything we are receiving.

The large commercial vessels do the same via their sat comms.
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Old 21 November 2018, 08:15   #72
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Satellite. I have a similar setup on our sailing yacht, only using mobile data - when within range of some form of 2G/3G/4G coverage, I can upload AIS positions for us and everything we are receiving.

The large commercial vessels do the same via their sat comms.
We had assumed/speculated it would have to be sat based comms.

So does your yacht have Class A I assume? Does it have SIM card in it or is it sent via on-board WiFi/234g setup?
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Old 21 November 2018, 08:22   #73
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No, sadly only class B on our sailing yacht.

There are some more modern AIS units with direct upload ability (via built in cellular/wifi connections) , but I just have a standard (must be something like 8 years old now) DigitalYacht AIS transponder interfaced to both a computer and the onboard plotters/instruments, and if I can get some form of network to the computer (typically a cellular-based router with a 3 SIM in it), then I can upload the AIS data whenever I have a connection.

I have a similar setup at home, but a super cheap NASA class-B receiver with an aerial mounted on the chimney connected to a knackered old computer that sits in a cupboard transmitting over the wifi network.
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Old 21 November 2018, 12:09   #74
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Thanks for info, all this came about because I was watching last tango and breezeblock vanish from one of the online AIS things up loch long. Their entire trip into loch goil wasn't there delaying getting the kettle on until they arrived back in range
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Old 21 November 2018, 13:02   #75
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Yes, there can be a massive difference in the coverage of receiving stations for online services like MarineTraffic - because this is often random people sticking aerials in their houses/gardens and uploading the data, as opposed to some official Coastguard type arrangement, some receiving stations are much better than others.

It's certainly noticeable along the south coast, where some aerials are stuck on RNLI/Coastguard/NCI antennas at ~150m height, and others in personal property at maybe only a few metres high.

Personally I just use a standard marine VHF aerial mounted on the house, but some people design their own monster antennas that do seem to be quite an improvement.

AIS class B transmitters only use low power (2W) as well, so very easy to drop off MarineTraffic, especially if in an area of lower coverage, and on a RIB with a fairly low mounted aerial.
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Old 21 November 2018, 15:40   #76
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I've been following this thread and also considering an ais transponder or an x band. We sail as well as rib. mark one eye ball is obviously the best but if someone goes missing on the ais for 1/2 hour i'd be really worried if the visibility is poo. We are sailing around ireland next year and i'm looking for kit I can rely on in poo weather and i'm now having my doubt about ais. Specially if you can turn it off, typically if your fishing,there are loads of fishing vessels off the irish coast...thoughts?? Nik
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Old 21 November 2018, 15:56   #77
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You wont go missing on AIS, you will maybe go missing on the online AIS sites, very different thing.

I don't know the regs for turning it off.
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Old 21 November 2018, 16:27   #78
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Agreed - for it's "intended" usage of direct vessel to vessel reporting, at close range there should be no issue with AIS, assuming it's turned on. Range for vessel to vessel depends on the aerials/aerial heights of both vessels, and the transmitting power (class A or B), so might not be more than a couple of miles in a bad case.

Online AIS tracking is completely different to the "intended" usage, and yes, you can go "missing" if you go out of range of a receiver that is uploading it's data to the internet. That doesn't affect what your receiver on your boat will see though in it's receiving radius.

Obviously 1.) AIS is only compulsory fit for certain vessels, so not everything will have it fitted anyway, and 2.) There is a "silence" button on it which turns off the transmit feature, or the unit may go faulty. I've seen Navy and Border Force ships come and go on AIS, but who knows how many other vessels choose not to transmit for various reasons!

Personally I wouldn't be without an AIS transceiver on our sailing yacht - makes cross Channel and coastal passages so much easier, to be able to easily see most of the commercial traffic and much of the leisure traffic, and also know we are broadcasting our position to many others. We do also use radar and passive and active radar reflectors though if visibility is really that bad, to try and ensure nothing is missed.

At the end of the day, however much fancy kit you buy and install, agree with your original comment - a good lookout is vital!
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