Intermittent AIS

[Bodach]

My AIS is transmitting the boat’s position intermittently. However I am receiving the positions of other vessels on AIS constantly on the chart plotter.

Can anyone suggest how I go about tracing the fault?

 

[cpedw]

Isn't that how AIS works? How intermittent is your intermittent?
If there are many other AIS sets nearby, your turn only comes round occasionally. And if you're class B even less frequently.

 

[FWB]

https://www.cactusnav.com/files/ClassB_SOTDMA_AIS_White_Paper.pdf

 

[wonkywinch]

How are you viewing your own signal? I thought I had a similar issue recently setting up a new to us boat. I could see other boats immediately but it took ages for it to transmit anything and at least a day before it showed up on Marine Traffic etc.

 

[Helidan]

My first thought was which AIS class are you operating? I assume class B.

 

[Bathdave]

I had this problem for a couple of years before I finally solved the issue …

I was seeing other ships close by (but not long distances) because the strength of the signal was picked up by the device itself not the ariel, sometimes I was transmitting and sometimes I wasn’t

turned out my stereo cd player/radio shared the aeriel with my VHF and my AiS but my signsal splitter was not picking up the stereo cd ..so if I used it it killed the ability of the splitter to send or receive AIs

took a long time, couple of trips up the last to check connections, lots of AIS diagnostics and head scratching

the moral of the story …take time to work out how everything interconnects and works

 

[DJE]

the moral of the story …take time to work out how everything interconnects and works

Or use a seperate AIS antenna.

 

[MontyMariner]

What model/make of AIS.
My em-trak indicates fault codes.

 

[Dunx]

Just sorting mine at the moment. No output but receiving and displaying other vessel info. The yard who lifted the boat this winter turned my antenna mount on the transom pole flat to reduce height in the travelhoist. It has cut the cable in doing so.

 

[shortjohnsilver]

Had this a couple of years ago. Ais displayed on plotter showing targets. However, other boats sailing within three or four miles could not see me, this was a bit disconcerting to discover having crossed a number of busy shipping channels!
Also, found that although I could clearly hear VHF transmissions, when I transmitted, no one could hear me! A much bigger concern as should I shout for help, no one would have heard.
Up and down mast several times, aerial changed, splitter checked and situation remained. Eventually swapped out the VHF cable entirely and all good. It seemed that the VHF cable had deteriorated partially allowing receipt but failing on transmitting.
Change your cable.

 

[johnalison]

Or use a seperate AIS antenna.

I checked mine yesterday. The performance with a splitter was not as good as it sometimes is. I was only receiving ship signals from about 35 miles over land.

 

[MontyMariner]

Still no reply from OP as to what AIS unit is fitted - AIS engine or integrated with his VHF radio.

 

[Bodach]

Apologies for the late response, have been out sailing. And thanks for all the responses.

Narrowed the problem down to either the GPS antenna OR the masthead aerial. Ruled out the latter by switching out to one of our spare aerials and thus concluded problem was with the GPS antenna. Bought a replacement on Amazon for £25, delivered to the boat. Instant fix, leaving only the palaver of routing the cable from the new antenna to the AIS unit.