Intermittent AIS issue ...any ideas on how to solve ?

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Bathdave

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I have an AIS transponder which goes through a signal splitter on my radio to the mast top aerial

it was working fine and getting everything I needed/expected when we crossed the channel to Cornwall in august and while we we there. I’ve had it for 3 years

on our crossing back, I noticed that i was not picking up the AIS transmissions from commercial ships until I was about 5 miles away, when I already had good ‘ eyes on’. On the outward crossing they had first appeared on my screen much further away, outside visual contact

I was puzzled ...

as we were approaching jersey at 3am I ideally flicked on my phone and marine traffic, I realised it was still showing me in Falmouth, and it was also showing 4 boats in the vicinity which were not visible by eye or on my screen..they eventually appeared on screen when I was 2-3 miles ..I radio checked the coast guard who could hear me but not see any AIS signal

a couple of weeks later I went for a spin around the bay and marine traffic picked me up

an electrical engineer friend came to have a look a month , we checked all the connections, I did a radio check and AIS ‘can you see me call‘ to the coast guard and got a ‘loud and clear’ response

took the boat out at the weekend, got the usual a ‘boat name leaving port of st Helier’ email from Marine Traffic, but after about 15 mins, there were no updates to MT. I called the coast guard, again no problem with radio reception but no AIS

i can see AIS images of other boats

so I seem to have an intermittent issue where AIS transmission stops, and my AIS receiving is weakened but not lost altogether

no sign my radio is malfunctioning, so my initial thought of aerial problem doesn't sound right the connectors are all push fit. Shortly before the issue started a rigger had been up the mast.

any bright ideas on what may be causing this ? im minded to think the signal splitter may be the problem but I’m a bit flummoxed
 
Marine Traffic depends on land based antenna.

May I suggest you go sailing in company and conduct some test on vessel to vessel transmissions.
 
thanks for your prompt response ...i was always within 1km of the shore on my trip this week, and 200 m from the coastguard office here in jersey when I checked with them, so I don’t believe that vessel to vessel is going to give a different result

i have always had a email ‘xxx is leaving port xxxx’ as I exit or arrive, before this started
 
You mention a splitter. What else shares the splitter? To rule out problems with the splitter try running the antennal cable direct from the AIS to the antenna. If the problem persists and affects both transmit and receive check the antenna connections between the AIS and splitter. You mention push connectors which concerns me as you should be using the correct bayonet or PL antenna connectors ensuring the centre inductor is soldered correctly and not just pushed into the fitting.
 
Bathdave said:
thanks for your prompt response ...i was always within 1km of the shore on my trip this week, and 200 m from the coastguard office here in jersey when I checked with them, so I don’t believe that vessel to vessel is going to give a different result

i have always had a email ‘xxx is leaving port xxxx’ as I exit or arrive, before this started
Click to expand...
VHF is basically line of sight. there might be something in the way. Hence the suggestion to do a vessel to vessel test. Both go out and sail away from each other until you can't see each other.

I've picked up big ships from 50 nm, I've actually seen a signal from 150 nm offshore on Marine Traffic, but am sure that was some strange stuff with the ionosphere.
 
Lots of issues when using internet based websites. It's all been said in previous posts. I'd be more concerned with the fact you didn't pick up other vessels while at sea until they were 2-3 miles away. Too close for comfort in poor visibility. Get/borrow a spare antennae (a proper one is best, not an emergency antenna) and connect it direct to the transponder. Hoist it up the mast or backstay on a convenient hoist line, spare halyard or other line. Then see how it works. Do some tests, go sailing. see how far off you're seeing things and make some radio calls to see if they see you. Then you'll know if its the transponder or the antenna/splitter system. Without test equipment, the process of substitution/elimination is the best route to find the problem.
Ignore the marine traffic and other websites. Its grossly unreliable and only as good as your location with regard to the shorestation. It can be a convenient method of seeing your boat when sat at home but not not to be relied on in any way in my experience.
P.S. You did say that all connections had been checked on the antenna system. Intermittent faults are sometimes, often caused by poor or loose connections. That would be my first check but you've already done it.
 
I'd go along with greeny - substitute with a separate antenna - its the first thing I would suspect having had in the past problem caused with a poor connection.
 
You haven't said what status lights are showing on the AIS unit. That can reveal an antenna or GPS problem.

Or hook up a laptop with the setup software and take a look at the diagnostics page. Try that with and without splitter as suggested by others.

Also second the idea of checking the centre cores are soldered into the pins if appropriate. Ideally remove them completely and refit if there's any doubt.
 
I assume that as it worked previously that it is the correct type of active splitter which is fitted? It must be one specified for AIS. I guess that an incorrect type of splitter, active or passive, might work for a while until a certain combination of AIS and VHF signals cause one of the components to fail.

Just a thought.

Richard
 
You say yourself that you have had your connectors checked and suspect the splitter. Easy to check this out just bypass the splitter and directly connect your AIS and monitor result.

Personally I prefer a dedicated pole mounted Ais antenna. We typically get up to 25miles receive and transmit with ours mounted at the same height as our radar scanner.

It can also be used as a high power emergency antenna by direct connection to the VHF with 25watt range and height significantly better results than a 5w handheld at deck level.

Are you sure your mast head antenna is in good condition? You can often get a call to the CG even with a pretty low power transmit. Try making a call to an alternative station without the benefit of a well positioned antenna or make use of a swr meter. Remember your AIS transmit power is less than a 10th of your vhf so any fault in your cable or MH Antenna will be affecting your ability to transmit.

As an aside I had recently left our transponder disconnected from the antenna. I was still receiving signals from local boats up to 2 miles away. I lost track of the red budgie sar at 5 miles! This prompted me to find the disconnect as I can usually track him for in excess of 30!
 
check that you have the correct type of splitter suitable for a transponder type AIS. Also, I had a friend with the same problem which turned out to be corrosion of the co-ax cable at the deck fitting. His VHF was OK but the AIS transponder had a very limited range.
 
What radio are you using? I have a standard Horizon which has AIS receive built in, as it already time shares the antenna, SH were strongly against me using any splitter for a transponder.
 
PaulRainbow said:
Might be useful t know what AIS and VHF we're talking about here. otherwise it's just guessing.
Click to expand...

I think we are all guessing here Paul as the OP has not replied to any questions since early December when it was suggested he tried connecting the antenna directly to the AIS for a check .
 
Don’t you just hate intermittent electric problems

never got to bottom of issue but it faded into background as seemed to be transmitting fine when I used the boat, and or requested a AIS check as well as a radio check from our friendly and helpful jersey coastguard

it was working and transmitting and I could see us when we set off for a day trip on Sunday, indeed I did an AIS with CG and I could see us on marine traffic as we left.

it stopped just as we got back after 12 hours out and has doggedly refused to send out a signal since ...we were in the harbour entrance but still underway when it stopped sending a signal

I have checked AIS unit and signal splitter and both appear to be operating ok (based on little indicator lights)

I AM getting AiS inputs from other boats onto the chart plotter, but possibly not at full range.

I have connected AIS directly to aeriel bypassing splitter and getting nothing on the transmission front

I am increasingly thinking an aerial issue, but my radio checks with CG are fine

my next step is to borrow an emrgency VHF aerial and attach it and see if that makes any difference.

any other bright ideas ?
 
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