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Old 15-07-2015, 03:20   #1
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Vanishing AIS target

Ok, just now pissed off with an AIS target that disturbed my relaxation by entering my safety zone. The target will appear on my MFD for perhaps 30 seconds and then disappear for 2 or 3 minutes. As a result it kept setting off my alarm.

It appears as type "unknown", no name, call sign or anything else that is programmed normally into a transponder, other than MMSI..

It has me wondering if the yacht is using an AIS TX that is designed for crab pot, It makes sense that a battery operated transmitter designed for a stationary object would shut down its transmitter to save battery.

Whilst for me in good daylight visibility it is just an annoyance, I could see that on the bridge of a ship in poor visibility that they might assume it is a stationary crab pot. if they are not going to run over its current position, they might either turn off the alarm or even the class B RX.

So saving money in safety might be a bad mistake.




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Old 15-07-2015, 03:33   #2
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Re: Vanishing AIS target

Do a MMSI search, this should help narrow it down.. https://en.wikipedia.org/wiki/Mariti...rvice_Identity
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Old 15-07-2015, 05:46   #3
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Re: Vanishing AIS target

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Originally Posted by El Pinguino View Post
Do a MMSI search, this should help narrow it down.. https://en.wikipedia.org/wiki/Mariti...rvice_Identity
Thanks El Pinguino-interesting info.

I was not aware that stuff,other than vessels,SAR,etc will be xmitting on AIS.

Won't be long & AIS screens will be cluttered with everything that floats,from crab/lobster pots to eejits with HH radios,etc,etc.

/ Len
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Old 15-07-2015, 06:11   #4
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Re: Vanishing AIS target

I googled the MMSI number and found the sailing boat in question which is registered a sailing boat. The thing is that AIS transmitters designed for fishing buoys can be programmed with a yachts MMSI and used on board. Assuming that the boat I encountered was using one of these devices then they are not fit to be repurposed onboard a yacht which should be discouraged


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Old 15-07-2015, 06:26   #5
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Re: Vanishing AIS target

I know long liners use this stuff Commercial Fishing Supplies | Radio Buoys and Beacons and even some that are on HF frequencies but I haven't heard of them using AIS on pot markers.... doesn't make a lot of sense... crab bandits would have a field day.

It would be nice if they fitted AIS to ODAS buoys... they scare me
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Old 15-07-2015, 06:39   #6
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Re: Vanishing AIS target

Whilst I understand on class A the transmit interval can be programmed, I don't know if B allows it.

I'm guessing that that yacht did not have Class A because he was sending less info than class B normally sends. So I'm inclined to think they went cheap with something like this.

http://m.aliexpress.com/item/3230163...bilesitedetail




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Old 15-07-2015, 06:48   #7
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Re: Vanishing AIS target

Interesting... but when I went here Online Shop high quality ais buoy for fishing net tracker position marine lucky fish finder good helper to find back the net 2015 hot sale|Aliexpress Mobile and saw what people also viewed and bought I thought that may be a fancy sort of electronic homing dildo... now that is scary...
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Old 15-07-2015, 06:54   #8
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Re: Vanishing AIS target

Golly... Marine GPS/AIS Fishing Net tracker, View high quality buoys, Huayang Product Details from Shenzhen Shenhuayang Electronic Technology Co., Ltd. on Alibaba.com

But it doesn't look as if they can be programmed ... a very strange bit of kit

How far away was the one that was vexing you? Maybe both just mounted low....

Dunno....
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Old 15-07-2015, 07:10   #9
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Re: Vanishing AIS target

I know someone from another forum who bought one which is how I know about it.

He could program it and had the option of outputting the battery voltage in the ships name. On marinetraffic his vessel type is "unknown" which is what made me start to think this boat is using the same.


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Old 15-07-2015, 07:11   #10
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Re: Vanishing AIS target

Quote:
Originally Posted by El Pinguino View Post
Interesting... but when I went here Online Shop high quality ais buoy for fishing net tracker position marine lucky fish finder good helper to find back the net 2015 hot sale|Aliexpress Mobile and saw what people also viewed and bought I thought that may be a fancy sort of electronic homing dildo... now that is scary...
Clearly you have a warped mind 😃

👍🏻


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Old 15-07-2015, 07:36   #11
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Re: Vanishing AIS target

Could be the other AIS is losing its GPS fix, and thus can't/won't broadcast position? The USCG has an eight year old notice about certain "non-approved" (read what you want as to place of manufacture) AIS units that are unable to process signals from newer GPS satellites (from PRN 32), resulting in intermittent AIS position reports.
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