AIS System - Where to Start?

[Refueler]

The Onwa plotter cost twice what I spent on the VHF, and would have required some re-wiring for antennas etc. I'm sure I can sort out a way to hold the VHF for me where I can see it when I'm helming, and it should give me what I need for now: basic AIS visibility.

OK - but VHF and Plotter / AIS are completely different worlds and with great respect - I think your 'path' is full of errors and will end up costing you more.

 

[GHA]

These delays are always multiples of 30s, I have the impression class B "sense" if there is an ongoing transmission every 30 seconds, if they find a carrier no message is sent and they wait another 30s before sensing it again. If the length of time they try and detect the carrier is short enough, they might well find it busy several times in a row. I have no idea if it is really the case but it's the only kind of plausible explanation I could find, happy to have more/different ones

Class B sends every 30s if speed is over 2kts or something, so unlikely it will be "trying again", it's just what they do. Static data is 6 minutes istr, this shows up on the logged data.
From logging class b targets can come and go, just not seen any data yet to indicate that this is because of too many targets, who knows...

This shows one this morning disappearing for an hour, though I know the boat & it was still on marine traffic with a receiver high up the hill.

 

[Jonny A]

OK - but VHF and Plotter / AIS are completely different worlds and with great respect - I think your 'path' is full of errors and will end up costing you more.

I don't have the money to spend at the moment on a 'proper' AIS/plotter set-up, and I don't think I really need one. In a few years time I hope to do more offshore sailing so I will need one, at which time I'll spend the money. I could try to stretch to the cheapest possible plotter-based AIS solution now, but in a few years the next generation of electronics will come along and it will have been a waste.

 

[Bilgediver]

Perhaps it does (or not), in one isolated function that only a shore station can perform.

Most VHF sets can send and receive position requests, i don't think that makes then transponders.

In normal use an AIS will just be a transceiver.

From what I can see AIS class A is the all singing and dancing model as we used on ships and oil rigs. There we had to keep updating data held regarding various details and I believe this was done using a laptop to enter cargo details and ports of departure and arrival. Not unusual for this to be overlooked and see vessels heading to incorrect destinations It seems some of the data is transmitted regularly and some on receipt of a request message.

Our class B units may not have these facilities. How many yachties interact with their AIS and update port of departure and arrival etc ?

It seems there is also an Extended Class B system available and looking at the attached this class uses some of the additional features in Class A and so will act as a form of Transponder. Yes DSC also does this and not called a transponder.

The AIS sends details that can be used by shore statons to calculate tidal data but does not appear to actually send tidal data . The ship sends heading and COG and tidal data is calculated from this.

Class B Transponders

 

[Supertramp]

Actual measurements of B messages "age", both other sailboats messages and my own (two different sources, I have separate txr and receiver, the receiver tells me how old is my last sent message). More visually, in busy places one can sometimes "see" on the plotter his own real time position above the AIS icon of another B boat which is actually a few hundred meters away.
Also, there is no need to have dozens of class A, it also happens with only Bs: typical summer day these are 99% class B, I put "Mark target as lost after 3 minutes", want to bet the barred icons are class B cstdma?
Anyway, not telling anyone to believe, maybe make one's own measurements and see what happens

View attachment 146598

Good grief! I think I would put my fenders out and ready the foghorn rather than worry about refresh rates.

I fitted AIS (Vesper standalone) and it works fine as far as I can tell. But the traffic I mostly use it for is big ships on passage. Much more useful and informative than radar. I guess I could be dropping in and out on their screens. The two most useful aspects for me are having the course and speed displayed at night so I can take a short nap with some confidence about where a set of lights is going. And the anchor alarm. It works on my Navionics display by WiFi but is more cumbersome and cluttered than the standalone unit.

For the OP, you will soon decide if you need more and can then prioritise among the inevitable costs of running a boat.

 

[Refueler]

I don't have the money to spend at the moment on a 'proper' AIS/plotter set-up, and I don't think I really need one. In a few years time I hope to do more offshore sailing so I will need one, at which time I'll spend the money. I could try to stretch to the cheapest possible plotter-based AIS solution now, but in a few years the next generation of electronics will come along and it will have been a waste.

Beiieve me when I understand where you are coming from .... despite my 'career and earnings' over the many years - I have always been one to try 'reduced cost' ways .... but eventually I had spent more and achieved less than biting the bullet and buying the integrated unit.
I have a suspicion that my 'diy' skills in this field may be more than yours ... so I was sure I could create my own path to solution. I still follow various 'paths' today ... such as the NMEA / WiFi / USB network I have on board ... but today instead of having all bits and bobs wired up .... _ now have the Onwa feeding the system and able to remove all that diy wiring ...... The VHF has its own built in GPS - that was a good move in itself.

If I was to replace my present systems with Garmin / Raymarine as example - the costs would be literally doubled. As many know on these forums - I am not a 'follower' of paying out for brand names .... I carefully weigh up where my cash goes ...

My Cobra M77 GPS VHF .... Onwa KP39A Plotter / AIS Tceiver ..... NMEA2WiFi unit ..... provides a budget but excellent setup. The total cost near equal to a single unit of usual brands mentioned ...

 

[Refueler]

Blimey ... what some people post !!

Most new AIS T'ceivers for yachts today are B+ .... not the older B format. This removes a lot of the previous limitations on update intervals etc.

For a Yottie ... and I put myself forward as not only an ex Senior Bridge Watchkeeper on ships - but also as a yottie for most of my life ... the value of AIS to me and I think for most others - is the info gained regarding OTHER vessels around and their risk factor to you. The Tx'g of your AIS and shown on other vessels systems is dare I say it - secondary. Most of those receiving any signal for you are most likely running a CAS Radar plot on you anyway.

OK - what systems on ships ? Usually integrated Radar display with AIS interaction .... with AIS dedicated TX / RX often a Text display unit that OOW would need to scroll through ...... As regards Ships info - that is input at start and end of voyage. Destination primarily and ETA. The position, speed and course being auto relayed from the multiple GPS units on board.

So far with regard to Yottie AIS - I see only In Port / At Sea options to choose and then unit auto integrates Position / Course / Speed in its Tx'g.

 

[PhillM]

Check out Onwa. I’ve borght a plotter AIS transponder in one unit. In the process of installing it atm. But on the face of it I’m very happy.

 

[slawosz]

I don't have the money to spend at the moment on a 'proper' AIS/plotter set-up, and I don't think I really need one. In a few years time I hope to do more offshore sailing so I will need one, at which time I'll spend the money. I could try to stretch to the cheapest possible plotter-based AIS solution now, but in a few years the next generation of electronics will come along and it will have been a waste.

I am not sure if it will get much cheaper for AIS devices, but there is a chance there will be more on the second market. Not sure how you are getting on with technology but using Raspberry Pi and 'black box' AIS you can construct quite a cheap Chartplotter. You might like to keep in touch with Onwa distributor, and let him know you are after used unit. As other mentioned, he is very dedicated and might help you.

 

[KompetentKrew]

From what I can see AIS class A is the all singing and dancing model as we used on ships and oil rigs. There we had to keep updating data held regarding various details and I believe this was done using a laptop to enter cargo details and ports of departure and arrival. Not unusual for this to be overlooked and see vessels heading to incorrect destinations It seems some of the data is transmitted regularly and some on receipt of a request message.

Our class B units may not have these facilities. How many yachties interact with their AIS and update port of departure and arrival etc ?

This is one of the major differences between class A and class B - class B transmits only boat name, speed-over-ground and direction, whereas class A can transmit other details as well, such as destination and rate of turn.

The vessel name is entered by the owner when they install the unit, so nothing else ever needs to be manually entered on a class B or B+ unit.

The vessel name is transmitted as static data every few minutes - I hadn't remembered that speed and direction are transmitted by class B more frequently than that but, knowing @GHA, I'm sure he's right to say so.

Most new AIS T'ceivers for yachts today are B+ .... not the older B format. This removes a lot of the previous limitations on update intervals etc.

I just searched Force 4 for AIS transponders and sorted from cheapest to most expensive - 13 of the products on the first page are actual transceivers (as opposed to splitters etc) and only two of them are class B+.

The cheapest class B is the Mcmurdo Smartfind M10 at £525, then there's a selection of other class B's at price points to £825. The cheapest class B+ is the Navico V3100 at £940 (it's marked as "SOTDMA" not B+, but this is the same thing). Of the 13 products in this survey, the only other class B+ unit is the Digital Yacht AIT5000 at £1350.

Surveying elsewhere I think the cheapest em-trak class B+ I can find is £750, but I could be wrong on this. I bought one of these myself earlier in the year - I don't remember seeing the Ocean Signal ATB1 before, but it seems bit of a bargain as a Black Friday megadeal of £585 - normal price is £850. (I can find a couple of other sites offering it for £790, so this does seem to be a legit bargain).

Considering this £200+ price premium for B+ and especially the existing user base of class B units (which have always seemed ok to me) I think it's only the minority you'll encounter in the wild that are B+ - my guess would be 1 in 10?

 

[Frank Holden]

Late to the party..
Transponders? Yes that is built into the system but not used very much.
However they can function as transponders - therefore they are transponders.
Only place I have seen it it used is Mejillones, Chile. As you cross into port limits you receive a happy little welcome message from the Armada.

 

[dankilb]

Surveying elsewhere I think the cheapest em-trak class B+ I can find is £750, but I could be wrong on this. I bought one of these myself earlier in the year - I don't remember seeing the Ocean Signal ATB1 before, but it seems bit of a bargain as a Black Friday megadeal of £585 - normal price is £850. (I can find a couple of other sites offering it for £790, so this does seem to be a legit bargain).

Very helpful survey. Think it helps explain why so many come back to em-trak- whether in terms of planning to buy (me!) or making the actual decision (you!). The em-trak with splitter works out about the same as the Black Friday Ocean Signal - once you add the cost of (reputable) splitter.

I have followed the thread from the start and I’m not sure a ‘cheap’ option has clearly emerged? If no plotter/existing system, Onwa sounds promising - but if adding to an existing system (plotter with nmea) and not wanting a separate aerial, there’s not much change from £500 (for a very DIY/Alibaba solution) or £1000 (from the mainstream).

 

[slawosz]

Very helpful survey. Think it helps explain why so many come back to em-trak- whether in terms of planning to buy (me!) or making the actual decision (you!). The em-trak with splitter works out about the same as the Black Friday Ocean Signal - once you add the cost of (reputable) splitter.

I have followed the thread from the start and I’m not sure a ‘cheap’ option has clearly emerged? If no plotter/existing system, Onwa sounds promising - but if adding to an existing system (plotter with nmea) and not wanting a separate aerial, there’s not much change from £500 (for a very DIY/Alibaba solution) or £1000 (from the mainstream).

Here is complete B+ box with aerials (gps + ais): Onwa KS200A AIS 'Black Box' for £500. Chartplotter with B+ is around £550.
Out of the box compatibile with mnea 183 and requires something for mnea2000.

 

[dankilb]

Here is complete B+ box with aerials (gps + ais): Onwa KS200A AIS 'Black Box' for £500. Chartplotter with B+ is around £550.
Out of the box compatibile with mnea 183 and requires something for mnea2000.

Thanks. I think I need to get over my fixation on splitting the masthead VHF aerial! A proper (I’m guessing active type?) splitter adds a couple of hundred quid. But form this thread it sounds like plenty prefer a separate rail mount aerial and get on well with it.

 

[slawosz]

Thanks. I think I need to get over my fixation on splitting the masthead VHF aerial! A proper (I’m guessing active type?) splitter adds a couple of hundred quid. But form this thread it sounds like plenty prefer a separate rail mount aerial and get on well with it.

My rail-mounted aerial shows ships quite far away. I didn't take photos when sailing, so can't really say. Plus, AIS antennas are operating on a bit different frequency (highest range of VHF) and apparently are better calibrated - I am not an expert so I can't say how true it is.

 

[TSB240]

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Probably the cheapest way to explore ais if you have a limited budget!
Add a twig on a pole and you should be U and running for under £125!
I suspect there will be many more cheap class b units on the market as people prefer to opt for sodtma or B+.

 

[Refueler]

Check out Onwa. I’ve borght a plotter AIS transponder in one unit. In the process of installing it atm. But on the face of it I’m very happy.

I'm sure you will like it ......

 

[Refueler]

This is one of the major differences between class A and class B - class B transmits only boat name, speed-over-ground and direction, whereas class A can transmit other details as well, such as destination and rate of turn.

The vessel name is entered by the owner when they install the unit, so nothing else ever needs to be manually entered on a class B or B+ unit.

You should have a data section as well to enter the type of and dimensions etc. of the vessel

The vessel name is transmitted as static data every few minutes - I hadn't remembered that speed and direction are transmitted by class B more frequently than that but, knowing @GHA, I'm sure he's right to say so.

Not much point in just sending name !!

I just searched Force 4 for AIS transponders and sorted from cheapest to most expensive - 13 of the products on the first page are actual transceivers (as opposed to splitters etc) and only two of them are class B+.

The cheapest class B is the Mcmurdo Smartfind M10 at £525, then there's a selection of other class B's at price points to £825. The cheapest class B+ is the Navico V3100 at £940 (it's marked as "SOTDMA" not B+, but this is the same thing). Of the 13 products in this survey, the only other class B+ unit is the Digital Yacht AIT5000 at £1350.

Surveying elsewhere I think the cheapest em-trak class B+ I can find is £750, but I could be wrong on this. I bought one of these myself earlier in the year - I don't remember seeing the Ocean Signal ATB1 before, but it seems bit of a bargain as a Black Friday megadeal of £585 - normal price is £850. (I can find a couple of other sites offering it for £790, so this does seem to be a legit bargain).

Considering this £200+ price premium for B+ and especially the existing user base of class B units (which have always seemed ok to me) I think it's only the minority you'll encounter in the wild that are B+ - my guess would be 1 in 10?

Blimey - I will never understand why people would pay such prices for 'Add-on' gear .... 'bargain' ???????

Onwa all in one Plotter - all Onwa have been B+ for last year or so .... is a lot less money than what you quote .......

My comment about near all are B+ today - was about most Plotters with inbuilt AIS, regardless of brand .....

 

[Refueler]

Thanks. I think I need to get over my fixation on splitting the masthead VHF aerial! A proper (I’m guessing active type?) splitter adds a couple of hundred quid. But form this thread it sounds like plenty prefer a separate rail mount aerial and get on well with it.

I was rail mounted separate antenna ... then fitted the Onwa Splitter - which is 'passive'. I rec'd many comments that I was wasting my time and 'passive' is just not worth it.

Well I can happily say that the tests I conducted showed that the 'passive' Onwa Splitter increased my target acquisition from 2 - 3 via rail mount - to over 11 targets via the spiltter. Connecting the masthead antenna direct without splitter gave me up to 19 targets. Boat location being on home mooring approx 3km upriver ... with residential area between boat and port area .....
This proved that once clear of land / houses etc. - the spillter based reception is preferable to rail.
Of course 'Active' Spiltter would remove the degradation of Tx and Rx power .... but why should I pay 3x the price for small gain ?

 

[slawosz]

Blimey - I will never understand why people would pay such prices for 'Add-on' gear .... 'bargain' ???????

Onwa all in one Plotter - all Onwa have been B+ for last year or so .... is a lot less money than what you quote .......

My comment about near all are B+ today - was about most Plotters with inbuilt AIS, regardless of brand .....

I presume most people buy AIS once in their life, and being used to marine prices, they prefer to buy in reputable chandlery than non-name brand from one person business.