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Old 24-12-2019, 14:01   #1
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Xmas AIS issues

Merry xmas all.
Satan bought me an AIS.

I have it up and running using the VHF antenna for now as a test (dedicated antenna has not arrived yet)
And the adapter plug for the external GPS has also not arrived yet so it is using the internal one.

Issue I have is this.

AIS can see fixed markers that are 40nm away
It can see the ferries that are running 3 miles away
It can see a couple of cargo ships tied up in port
It can see a few anchored vessels nearby.

What it can't see are the vessels with AIS in the same anchorage
Or the dozens that are in the marina 15 miles away
Or the dozens that are in several other anchorages within 10nm of our location.

Any ideas?
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Old 24-12-2019, 14:13   #2
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Re: Xmas AIS issues

Quote:
Originally Posted by Simi 60 View Post
Merry xmas all.
Satan bought me an AIS.

I have it up and running using the VHF antenna for now as a test (dedicated antenna has not arrived yet)
And the adapter plug for the external GPS has also not arrived yet so it is using the internal one.

Issue I have is this.

AIS can see fixed markers that are 40nm away
It can see the ferries that are running 3 miles away
It can see a couple of cargo ships tied up in port
It can see a few anchored vessels nearby.

What it can't see are the vessels with AIS in the same anchorage
Or the dozens that are in the marina 15 miles away
Or the dozens that are in several other anchorages within 10nm of our location.

Any ideas?
I can see all vessels
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Old 24-12-2019, 14:24   #3
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Re: Xmas AIS issues

Not strictly related but can you see your own vessel on the AIS internet sites:

Marine Traffic

Vessel finder

Took my installation about 3 days to appear on Marine Traffic, Vessel finder was a few hours from first transmission.

and can you see other yachts nearby say 5 miles on the AIS internet websites to check if they are transmitting.

Does it use the AIS Pro2 software that many do? if so does this software report lots of green ticks in the test screen?
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Old 24-12-2019, 14:33   #4
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Re: Xmas AIS issues

You are receiving the 13m yacht Songlines:

https://www.vesselfinder.com/vessels...MMSI-503019510
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Old 24-12-2019, 14:49   #5
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Re: Xmas AIS issues

Quote:
Originally Posted by Pete7 View Post
Not strictly related but can you see your own vessel on the AIS internet sites:

Took my installation about 3 days to appear on Marine Traffic, Vessel finder was a few hours from first transmission.
Not yet



Quote:
and can you see other yachts nearby say 5 miles on the AIS internet websites to check if they are transmitting.
I have a vessel pinging away within 200 metres of me.
Saw them come in yesterday but then they vanished.
Quote:
Does it use the AIS Pro2 software that many do? if so does this software report lots of green ticks in the test screen?
No idea but I would say no.
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Old 24-12-2019, 14:53   #6
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Re: Xmas AIS issues

Quote:
Originally Posted by Pete7 View Post
You are receiving the 13m yacht Songlines:

https://www.vesselfinder.com/vessels...MMSI-503019510
Yep.

But none of these 15nm away
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Old 24-12-2019, 15:03   #7
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Re: Xmas AIS issues

They are likely transmitting at 2w, is the geography stopping the signal reaching you?

Pete
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Old 24-12-2019, 15:07   #8
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Re: Xmas AIS issues

Quote:
Originally Posted by Simi 60 View Post
Yep.

But none of these 15nm away
As Pete said, these are likely low power class B units. Think more like 5 miles on these, with exceptions.
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Old 24-12-2019, 15:16   #9
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Re: Xmas AIS issues

Also, don’t necessarily believe the 40 mile report from the AtoN. Many AtoN do not broadcast themselves, instead the information is broadcast from a base station. Australia has a lot of those, and they are also used as repeaters, so distance from the mark may or may not be distance from the antenna that broadcast it.

I find class B is about 10 miles in open water, but frequently much (much) less once land gets involved.

PS in that internet shot you can drill down to find the base station that is reporting those targets and figure out how far that is from the targets - gives you an idea of range.
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Old 24-12-2019, 15:23   #10
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Re: Xmas AIS issues

Quote:
Originally Posted by Pete7 View Post
They are likely transmitting at 2w, is the geography stopping the signal reaching you?

Pete
Clear line of sight apart from the 2m rock wall surrounding the marina.

I didn't realise they or most things transmit at a lower power, I figured if I can see something 40nm away I should see everything in between but apparently not?

Given the explanations so far perhaps it is working as advertised?
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Old 24-12-2019, 16:30   #11
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Re: Xmas AIS issues

Yes absolutely it is. ATONs are usually transmitted in other ways, and you will "see" them from a ridiculous distance as they aren't really AIS devices like a boat. Often they are entirely virtual (i.e. their signal is being transmitted from land, not from where they are).

Big ships will be transmitting at high power over class A with big aerials, and you'll see them from at least 10 if not 20 miles out. Little ones will be transmitting much shorter distances, sometimes less than 5 miles if you're near the coast. And a whole lot of boats will tend to have their AIS off entirely if they're in a marina so they won't even be transmitting.

In my local harbour I can see (on AIS) a few yachts in the marina, all the small boats in the inner harbour, all the big boats either moored or way out to sea for 15 miles or more, and all the ATONs as far as they go. It's working fine.

I can't see why you would want to clutter up your AIS system with dozens of small boats that are moored in a marina 15 miles away. How do you intend to hit them exactly?
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Old 24-12-2019, 16:39   #12
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Re: Xmas AIS issues

Are you able to pick up a big red sleigh with eight small blobs in front? 😀
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Old 24-12-2019, 16:54   #13
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Re: Xmas AIS issues

Quote:
Originally Posted by Tillsbury View Post

I can't see why you would want to clutter up your AIS system with dozens of small boats that are moored in a marina 15 miles away. How do you intend to hit them exactly?
I dont
But I did want to see them to make sure it was working in the manner that I though it would.
Then I can adjust settings to disable moored/not moving vessels.

I still haven't figured out why a vessel a couple of hundred metres away, happily pinging away on marine traffic every few minutes is not showing up.
The whole concept of AIS (Apart from govt tracking our movements) is to see boats that are close so as to avoid collision right?
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Old 24-12-2019, 17:19   #14
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Re: Xmas AIS issues

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Originally Posted by Simi 60 View Post
I still haven't figured out why a vessel a couple of hundred metres away, happily pinging away on marine traffic every few minutes is not showing up.
That specific part would concern me too. If you see them on MT and they show an update every few minutes on MT then you can be pretty sure they are transmitting.

Do you have a different antenna you can connect, even a little rubber ducky (while you wait for the new antenna)? It would appear that the unit itself is likely working since you get some targets, so antenna is where I’d start.
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Old 24-12-2019, 17:30   #15
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Re: Xmas AIS issues

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Originally Posted by Simi 60 View Post
I still haven't figured out why a vessel a couple of hundred metres away, happily pinging away on marine traffic every few minutes is not showing up.
Do you perhaps have software settings to suppress anchored or moored targets being displayed?

Many AIS units and software that displays AIS has suppression features (eg for anchored/moored AIS targets except for ATONs and those transmitting status as NUC).
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