Cheap/Easy AIS transponder

[Sos]

Originally Posted by Emmalina

The Matsutec is a great product and it is a plotter but without maps !

The Onwa is a plotter and it comes with free charts!


Connected mine to the Zeus 2 at the helm so we can see targets there as well.

[s/v Jedi]

Originally Posted by IslandHopper

I thought that was fairly well know these days, a quick look at MarineTraffic will clear that up.

I should add that AIS Transponders have not been designed with the aim of transmitting to Satellites, they are still a terrestrial transponder, satellites have been launched with receivers aimed at picking up the AIS signals.

Yes, but when they added msg27, the number of position updates received by satellites that were designed to listen for that msg on those channels multiplied by a large number, like 5x as many IIRC.

There is a book Satellite AIS for Dummies that I can recommend. I got it for free from ExactEarth, which is a good source of info.

All that said, my position is still available via satellite even though I have an old class-B CS box from Vesper.

[longjonsilver]

Originally Posted by s/v Jedi

There is a book Satellite AIS for Dummies that I can recommend. I got it for free from ExactEarth, which is a good source of info.

i am having trouble finding it. Can you give us a link?

thanks

[longjonsilver]

Nevermind, i found it. Here it is:

Satellite AIS For Dummies

jon

[BillKny]

Originally Posted by s/v Jedi

Contrary to what you guys think, class-A as well as class-B SOTDMA AIS transponders do send messages to satellites. These are the so-called msg27 transmissions, designed for long range AIS and are broadcast every 3 minutes on VHF channels 75 and 76. These two channels have frequencies centered around channel 16, which also means that they need a wideband antenna that is suitable for AIS as well as VHF, like the Vesper antenna.

Jedi,

Of COURSE they all send radio tranmissions that just happen to reach satellites, and there are a few satellites that can receive and decode the mess and (ultimately) post it to places like Marine Traffic.

However, none of the AIS transmitters were designed to do this including the SOTDMA models. It is just a side benefit of the sea-level technology that is poached by the satellite sellers of data.

I have never seen a Class B vessel shown offshore on Marine Traffic (or other AIS consolidation website). Certainly my boat never shows up on Marine Traffic when out of range of shore stations. I know it is coming technology, but as far as I know, it is not here--yet.

The whole AIS system is a nightmare of confused data when it's collected from a satellite because ships that are over each other's radio horizon can not directly coordinate on timing of AIS transmisssions.

Down on earth, this can be a problem with even three ships, two of which are out of range of each other. This was the real reason for SOTDMA, to give a system where ships that are out of range of each other can still avoid stepping on each other's digital transmissions. This makes the satellite problem a BIT easier, but still hard...

If you can show me someplace in the AIS specification where the communication with satellite receivers is discussed and built in to the design, I'll happily eat crow...

[muttnik]

Originally Posted by BillKny

If you can show me someplace in the AIS specification where the communication with satellite receivers is discussed and built in to the design, I'll happily eat crow...

I wasn't aware of this until this thread (thanks s/v Jedi) but:

https://www.itu.int/dms_pub/itu-r/op...2009-PDF-E.pdf

Is there such a substance as tofucrow? I'd be happy to try that...

[AedanC]

Originally Posted by BillKny

I have never seen a Class B vessel shown offshore on Marine Traffic (or other AIS consolidation website). Certainly my boat never shows up on Marine Traffic when out of range of shore stations. I know it is coming technology, but as far as I know, it is not here--yet.

Using MarineTraffic and satellite positions I have successfully followed a friend with class B from Tenerife to Ireland in 2019. He has a class B transceiver. His position updated 4-8 times per day.

Aedan

[Statistical]

Originally Posted by muttnik

I wasn't aware of this until this thread (thanks s/v Jedi) but:

https://www.itu.int/dms_pub/itu-r/op...2009-PDF-E.pdf

Is there such a substance as tofucrow? I'd be happy to try that...

I think there is a miscommunication. YES AIS signals can be received by satellites and significant improvements have been made to increase the reliability and coverage of those sat receptions in the last decade or so.

However AIS was never built with satellite reception in place. It was 100% intend as a local traffic management and collision avoidance system. Development began in 1990 and the first experimental satellite payloads to see if sat reception was viable didn't happen for well over a decade later.

[IslandHopper]

Originally Posted by s/v Jedi

Yes, but when they added msg27, the number of position updates received by satellites that were designed to listen for that msg on those channels multiplied by a large number, like 5x as many IIRC.

There is a book Satellite AIS for Dummies that I can recommend. I got it for free from ExactEarth, which is a good source of info.

All that said, my position is still available via satellite even though I have an old class-B CS box from Vesper.

Yep, what i should have said was, there is nothing designed in the AIS units capability in transmitting to a satellite, or a satellites ability in detecting AIS signals, that benefits the user on there vessel when it comes to collision avoidance etc, it is still a terrestrial designed unit and all the information presented to the user is such.

[s/v Jedi]

Well, maybe you read the ITU specification on Satellite AIS first before commenting that it doesn’t exist or download the free book I linked to earlier.

Msg 27 is not transmitted on the normal AIS channels and it is designed for satellites. No matter how many times you repeat it is not

[IslandHopper]

Originally Posted by s/v Jedi

Well, maybe you read the ITU specification on Satellite AIS first before commenting that it doesn’t exist or download the free book I linked to earlier.

Msg 27 is not transmitted on the normal AIS channels and it is designed for satellites. No matter how many times you repeat it is not

You are obviously having trouble understanding what i posted mate! i am well aware of Msg 27 and what it does, I've never stated otherwise, i have already pointed out that Sats have been tracking AIS for some time, the shipping company i work for have been tracking there own fleet for years as do most shipping companies, i didn't disagree with your statement that Msg 27 has increased the satellites ability to track more AIS targets cause i know it to be true!

What i am saying is it makes bugger all difference to the AIS user, especially the recreational user! whats so hard to understand about that?

....and no i haven't read anything you have linked to, i don't have to, we get notified about stuff like this when as and when it happens, i'm sure i could dig through the ships library and find way more on the subject.

[George_SD]

Cheapest AIS transponder that I can think of is the iCOM M94D

$300 handheld AIS+VHF with DSC

https://www.westmarine.com/buy/icom-...3?recordNum=17

[Simi 60]

Originally Posted by George_SD

Cheapest AIS transponder that I can think of is the iCOM M94D

$300 handheld AIS+VHF with DSC

https://www.westmarine.com/buy/icom-...3?recordNum=17

Transceiver
Not transponder.

[Simi 60]

I got a Matsutec HA102 a couple of years ago
Easy to install
Easy to program

About $300



https://www.aliexpress.com/i/32607679896.html

[muttnik]

Originally Posted by Statistical

I think there is a miscommunication. YES AIS signals can be received by satellites and significant improvements have been made to increase the reliability and coverage of those sat receptions in the last decade or so.

I think we're all aware that AIS was designed for operation within VHF range on the earth's surface. Those who have dug a little deeper and wondered how satellite AIS reception works will also be aware of how that original protocol design causes issues for satellite reception because of the massively increased area over which satellites are receiving.

What I *hadn't* read up on until this thread was what the ITU had proposed to go some way to mitigating those issues, ie the addendum to the AIS spec specifically to facilitate satellite reception of AIS data, the proposal for which was the link I posted.

What I'm still unclear on is adoption of that recommendation. It certainly seems there are now satellites which can receive message 27 on channel 75/76:
https://artes.esa.int/news/new-satel...tracking-ships
https://www.sciencedirect.com/scienc...94576516305938
..but how widely adopted this is in current AIS transceivers I have no idea (if anyone knows....)

So here's the summary of what I understand and if anyone wants to point out where I'm in error, let me know :-):
* AIS wasn't designed for satellite reception
* It can be received by satellites (without that pesky spherical earth getting in the way), but overlaps caused by wide reception area and propagation delay are problematic
* The protocol has been augmented with a new facility expressly designed to mitigate some of the observed problems with satellite reception (what s/v Jedi posted about)
* Satellites able receive message 27 on the "new" channels are in orbit
* I'm personally unaware of how widely this tech is deployed in transceivers or if the ITU recommendation that it be limited to class A was adhered to (I'm guessing yes)
* Satellites still also receive the old, problematic way (and class B satellite reception exists)