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Old 26-07-2012, 10:31   #1
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AIS position reports but (almost) no Static reports?

I got a bit of a mystery with AIS static data here, not sure if this is common? Someone has run into this before?

I installed an AIS Class B transceiver on a boat that's in a marina 200m from where I work. It has a ~6' whip antenna and 2 spliced co-ax cables connecting it, I soldered the connections myself, for better or for worse. 20 minutes after powering it up, I get position reports from about 50 vessels but static reports (ship name etc.) from about 3-5 vessels. I'm missing a huge amount of static reports. At work, a few hundred meters away, our AIS receiver picks up about 100 vessels, all with static data too.

I was thinking maybe because I was in a marina surrounded by radio obstacles that maybe the position reports were coming through because they were smaller, single-packet messages and less prone to inerfereance destroying them. The static data messages come in multiple packets so maybe there's a higher chance of one of them getting corrupted. I took the boat out into the middle of the commercial harbour, within 2 miles of at least 50 vessels with AIS. Again, 20 minutes later, very few vessel names appearing.

But what's weird is I can pick up AIS position reports from ferries 18 miles away but no names from tankers 200 yards away.

So I thought maybe something was crazy with my DIY co-ax splices so I took a 2nd antenna out there with an off-the-shelf cable. Same thing.

What's going on? Has anybody had this happen?

Thanks for any tips or insight!
ngermain is offline   Reply With Quote
Old 26-07-2012, 17:31   #2
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Re: AIS position reports but (almost) no Static reports?

You may just need to wait a little longer. Static data is xmitted every 6 minutes. With that many vessels near you, it may take a while for the packets to get thru.

fairbank56 is offline   Reply With Quote
Old 26-07-2012, 18:07   #3
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Re: AIS position reports but (almost) no Static reports?

It may also be overload. I have seen receivers that got overcrowded and then they selected the data based on proximity.

BTW ask the manufacturer, perhaps there is/will be a software update that will sort out your issue.

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