AIS installation

[MontyMariner]

it struggles with smaller vessels in a big sea even in as little as 3 miles.

3 miles is more than adequate unless they (or you) are doing 30 knots!

 

[gaylord694]

Hello, I'd like to install AIS on my Sadler 29 before my planned passage over the North Sea next summer. I have a VHF radio on the boat and my question is this: is it possible to buy an AIS receiver and share the same VHF aerial via a splitter in the cable? Or, as a friend has on his boat, is it better to
buy a fancier radio that has AIS built in? Thanks, E

Hello, I'd like to install AIS on my Sadler 29 before my planned passage over the North Sea next summer. I have a VHF radio on the boat and my question is this: is it possible to buy an AIS receiver and share the same VHF aerial via a splitter in the cable? Or, as a friend has on his boat, is it better to
buy a fancier radio that has AIS built in? Thanks, Eric

Hi Eric install an Em-trak 952..... I've a Metz AIS masthead antenna and you really can't go wrong ......There customer service is first class , Bluetooth connection and you can install onto a tablet of your choice ... . As the saying goes buy cheap ,buy twice and I certainly think when it's one of the most important components on the boat to keep you safe there's no compromises to take

 

[john_morris_uk]

3 miles is more than adequate unless they (or you) are doing 30 knots!

I’d be really unhappy if my AIS only gave me targets 3 miles away. Ships often start taking an interest in targets at six miles away or more and I like to see what they’re doing.

And for those who mistakenly believe ships don’t track AIS B, my experience is that they most certainly do.

I still maintain that AIS is a brilliant tool. It’s convincing a new generation of boat owners that most every ship is not about to run them down but that when they’re the give way vessel, they’ve invariably tweaked their course a fraction to open up the CPA. Something that took a long time to become apparent when using a hand bearing compass.

PS to the OP. My preference is AIS class B using a powered splitter at the masthead. You gain far more in range than you lose in any slight losses in the splitter. And FWIW we use the Raymarine units that talk to each other.

 

[Refueler]

My preference is AIS class B using a powered splitter at the masthead. You gain far more in range than you lose in any slight losses in the splitter.

As a Yottie - you have no choice but use Class B / B+ if you want AIS transceiver - you are forbidden to use Class A.

As regards powered ..... Active .... splitter ... its powered specifically to counter losses ... to improve AIS signal transmit / reception ...

 

[gaylord694]

As a Yottie - you have no choice but use Class B / B+ if you want AIS transceiver - you are forbidden to use Class A.

As regards powered ..... Active .... splitter ... its powered specifically to counter losses ... to improve AIS signal transmit / reception ...

Is it a law as I thought you just had to be over 300 tonnes..... It would be nice to know

 

[john_morris_uk]

As a Yottie - you have no choice but use Class B / B+ if you want AIS transceiver - you are forbidden to use Class A.

As regards powered ..... Active .... splitter ... its powered specifically to counter losses ... to improve AIS signal transmit / reception ...

Are you sure about that? Over 300 tonnes etc it's mandatory but I am not sure that small craft are actually forbidden from using Class A. it's unusual as its a) expensive b) a PITA as you are supposed to feed in details of your passage with your cargo etc. However I know of several 'larger' yachts who run Class A for better or worse.

 

[gaylord694]

I know of several small yachts under 40ft which use class A. Like I said I don't think it's illegal, just major overkill

 

[Refueler]

Are you sure about that? Over 300 tonnes etc it's mandatory but I am not sure that small craft are actually forbidden from using Class A. it's unusual as its a) expensive b) a PITA as you are supposed to feed in details of your passage with your cargo etc. However I know of several 'larger' yachts who run Class A for better or worse.

Class A is designed and intended for Commercial .. and can be used on small craft - but that would usually indicate they are for 'hire ... carrying goods / people' ...
I cannot find any mention 'forbidding' it - so I agree my wording may have been an error ... but my question would then be why would a craft that does not fall into such commercial category go to expense of Class A ? I can partly understand when only Class A and Class B were the fromat ... Class B was lower power ... did not slot in as A does etc. - but that has been solved with the Class B+ which uses same slot access as Class A and similar power ...

 

[RogerJolly]

I thought an active splitter was mandatory, over passive.

This on the grounds that you need to guard against the AIS transmissions going back up the radio rf output and blowing it up, so some active switching is necessary.

Is that not right?

 

[Refueler]

Ok .. I will return back to OP's question of what to do ...

Given today the widespread use and benefit of Chart Plotters ... and that AIS is integrated into the plotter with various manufacturers - something that I find hard to understand why mainstream more expensive do not do ... but anyway.

For the price of a good VHF set without AIS ... you can buy a Plotter with integral AIS transceiver with Class B+ ... or even cheaper if you go for end of line Class B sets ... the plotters come with free charting that I have yet to find fault with and I use many different forms of charting including full commercial. You can insert Navionics / CMap (depends what set which charts) ...
A multiplexor such as the NMEA4WiFi can take all info from that plotter and send out via USB ... NMEA .... WiFi all data to guests phones / other plotters / units ...
A splitter to have AIS use the same antenna as the VHF ...

My setup in use today is now end of line but illustrates well :

Onwa KP39A -
K-Chart 2.0, K-Chart 3.0, C-Map Max, Navionics + charts. · Automatic route log for 8,000 points, ability to track the vessel's route in both directions.

NMEA2WiFi - accepts all NMEA data from the Onwa and distributes out to >

Garmin UHD 92 via NMEA cable - I did not separate out GPS - but that's easy to do if desired. All AIS data is shown
8" Android tablet running Navionics Boating App ... all AIS targets displayed .. all via WiFi
Samsung A34 smart phone - same as tablet. All via WiFi
PC based charting via USB - displays all data incl AIS
and to any guests who may be on board and have charting etc on their phones.

The cost ? about 400 for the plotter ... 50 for the Multiplexor ... I was asked to test the Onwa Splitter but that is about 100 if you buy ... total I installed : 550 quid ... then add another 50 quid for the whole Baltic Navionics for Boating App.
The tablet and PC were already in use ... my VHF was swapped out for a SH DSC unit I had already to replace the ancient set ...

Why would I want to pay out for VHF with AIS - then sort out other units etc. ???

 

[Refueler]

I thought an active splitter was mandatory, over passive.

This on the grounds that you need to guard against the AIS transmissions going back up the radio rf output and blowing it up, so some active switching is necessary.

Is that not right?

I don't know where you get your idea from ....

OK ... there are Passive splitters that are only designed for low power on both signals - they are just plain RF splitters ... I have one that was intended for other use ... it should never be used for 25W VHF / 5W AIS service ...

Here is RF splitter - which sits in the band - but should never be used for VHF - AIS :

Here is the internals :

Other side basically resistors and diodes ....

But a Passive splitter designed for VHF / AIS use does protect the two units from each other ... the only factor it does not do - is boost the signals out / in. I have the Onwa passive splitter :

KA-Splitter - ONWA Marine Electronics Co. Ltd.

Onwa slongside the plain RF splitter :

Internals :

As you can see - different altogether ...

Powered Splitters are powered to BOOST and counter losses in switching / transmission .....
The advantage of Active (powered) vs Passive (non powered) is probably in range of 10 - 20% .... because no matter what it does - it is limited to the max allowed output of the VHf and AIS ... in theory the Active splitter is designed to give you what a dedicated antenna without splitter would give you at same height etc.

 

[gaylord694]

Class A is designed and intended for Commercial .. and can be used on small craft - but that would usually indicate they are for 'hire ... carrying goods / people' ...
I cannot find any mention 'forbidding' it - so I agree my wording may have been an error ... but my question would then be why would a craft that does not fall into such commercial category go to expense of Class A ? I can partly understand when only Class A and Class B were the fromat ... Class B was lower power ... did not slot in as A does etc. - but that has been solved with the Class B+ which uses same slot access as Class A and similar power ...

There's a certain individual I know who has it so he can boast what he's got and how better it is than anyone elses..... If you have a black cat he's got a blacker one !

 

[Refueler]

There's a certain individual I know who has it so he can boast what he's got and how better it is than anyone elses..... If you have a black cat he's got a blacker one !

I know a few people like that !! I just shrug shoulders .. and move on ...

Maybe tell him about Class B+ ??

 

[Pye_End]

Hello, I'd like to install AIS on my Sadler 29 before my planned passage over the North Sea next summer. I have a VHF radio on the boat and my question is this: is it possible to buy an AIS receiver and share the same VHF aerial via a splitter in the cable? Or, as a friend has on his boat, is it better to
buy a fancier radio that has AIS built in? Thanks, Eric

I used a little cheap rubber antenna on the pushpit on first NASA receiver install, and got 3+ miles. Chanaged for a Metz on the pushpit and get way in excess of 7miles (I'll check the range when next up). The range is more than enough to need, and is only really there for interest - although the longer range is handy offshore, singlehanded, as it is comforting when you desire to go to sleep.

The advantage of a separate, decent, VHF antenna for the job is that it is a spare in case the masthead one fails, or the rig comes down. It can be connected up to both my handheld and the main set if necessary.

Having had an antenna fall apart in a gale I can confirm that masthead antenna failure can happen, inevitably in the most irritating of circumstances.

 

[Refueler]

I have both masthead and pushpit mounted VHF antenna's on my 25ft'r ... a hang over from when I had AIS Rx to the rail antenna. Later before I bought the 38ft'r ... I upgraded to splitter to masthead with the installation of the Onwa.

The rail antenna on a calm day without significant swell - I could get about 7 - 10nm targets depending on their antenna height of course. But as soon as seas started .. that range soon dropped and in any significant swell - the AIS was often blank ...
The Onwa then transferred to the 38ft'r leaving the rail antenna behind.

The 25 having now been repaired ... its stbd bilge keel. She will be used on the river and unlikely to venture to sea again. The antenna will be removed from rail and moved to my 24ft MoBo ...
Haven't decided which radio to fit on the mobo yet ... no need for AIS on it as it will not venture out that much to sea .. except when calm for a bit of fishing.

 

[Blue Seas]

Rather than start a new thread - can I ask an AIS question. Does anybody know (or would care to guess) the difference in range (given identical met conditions) of transmitting @ 2W versus 5W versus 12W i.e. Classes B, B+ and A ?

 

[GHA]

Rather than start a new thread - can I ask an AIS question. Does anybody know (or would care to guess) the difference in range (given identical met conditions) of transmitting @ 2W versus 5W versus 12W i.e. Classes B, B+ and A ?

For technical things like that these days you`ll probably find asking an AI is just better all round, https://www.perplexity.ai will give the answer and links to all the sources it used to create the reply. Seems to help logging in & giving it some context. And doesn't bicker

"the difference in range (given identical met conditions) of transmitting marine AIS @ 2W versus 5W versus 12W i.e. Classes B, B+ and A ?"

Answer
The range differences between marine AIS (Automatic Identification System) Classes B, B+, and A largely stem from their transmission power and technology. Here's a detailed comparison of the three classes based on their transmitting power and expected range under identical meteorological conditions.

Transmission Power and Range​

Class A​

• Power Output: 12.5 Watts
• Range: Typically up to 20-30 nautical miles, depending on conditions and antenna height. Class A transponders are designed for larger vessels and transmit more frequently, which enhances their visibility.

Class B​

• Power Output: 2 Watts
• Range: Approximately 8-10 nautical miles. This limited range is due to the lower power output and the fact that Class B transponders transmit less frequently (every 30 seconds when underway) and must yield time slots to Class A transmissions in busy waters
  1
  2
  3
  .

Class B+ (also known as Class B SOTDMA)​

• Power Output: 5 Watts
• Range: Generally extends to about 12-15 nautical miles. The increased power not only enhances the transmission range but also allows for more frequent updates based on vessel speed, improving situational awareness in congested areas
  2
  4
  5
  .

Summary of Differences​

AIS Class	Power Output	Typical Range	Transmission Frequency
Class A	12.5 Watts	20-30 nautical miles	Frequent, varies with speed
Class B	2 Watts	8-10 nautical miles	Every 30 seconds
Class B+	5 Watts	12-15 nautical miles	Varies with speed, more frequent than Class B

Key Features Impacting Range​

1. Transmission Technology:
   • Class A uses Self Organised Time Division Multiple Access (SOTDMA), which allows for efficient slot management in busy areas.
   • Class B transponders use Carrier Sense Time Division Multiple Access (CSTDMA), which can delay transmissions if a Class A signal is present.
   • Class B+ adopts SOTDMA, giving it priority similar to Class A, allowing for more reliable transmissions in congested waters
     1
     3
     .
2. Update Rates:
   • Class A transponders adjust their update rates based on speed, providing frequent updates for fast-moving vessels.
   • Class B transponders have a fixed update rate which can lead to significant gaps in position reporting for faster vessels.
   • Class B+ improves upon this by adjusting update rates based on speed, allowing for better tracking of fast-moving vessels
     2
     4
     .

In conclusion, the choice between AIS Classes should consider the vessel type, operational area, and specific needs for visibility and communication. For smaller recreational boats operating close to shore, a Class B may suffice; however, for vessels venturing further offshore or operating at higher speeds, investing in a Class B+ or even a Class A transponder may be warranted for enhanced safety and visibility.
Share
Rewrite

https://www.cactusnav.com/files/ClassB_SOTDMA_AIS_White_Paper.pdf
AIS B+ explained: How to see and be seen on the water - Motor Boat & Yachting
What is AIS Class B+ and do I need it for my boat? - Practical Boat Owner
Les nouveaux transpondeurs AIS classe B+ expliqués – Navigation Mac
https://digitalyachtamerica.com/product/ait5000/
https://oceantimemarine.com/en/class-a-and-class-b-automatic-identification-system-ais/
https://www.cruisersforum.com/forums/f13/class-b-ais-units-269595.html
https://avesmarine.com/blog/ais-explanation/

Also, with a raspberry pi onboard graphing the max distance to targets range wil constantly vary with conditions a bit, or a lot when tropospheric ducting kicks in & it can go to hundreds of miles in a few minutes.

 

[Blue Seas]

For technical things like that these days you`ll probably find asking an AI is just better all round, https://www.perplexity.ai will give the answer and links to all the sources it used to create the reply. Seems to help logging in & giving it some context. And doesn't bicker

"the difference in range (given identical met conditions) of transmitting marine AIS @ 2W versus 5W versus 12W i.e. Classes B, B+ and A ?"

https://www.cactusnav.com/files/ClassB_SOTDMA_AIS_White_Paper.pdf
AIS B+ explained: How to see and be seen on the water - Motor Boat & Yachting
What is AIS Class B+ and do I need it for my boat? - Practical Boat Owner
Les nouveaux transpondeurs AIS classe B+ expliqués – Navigation Mac
https://digitalyachtamerica.com/product/ait5000/
Class A And Class B Automatic Identification System (AIS) – Ocean Time Marine
https://www.cruisersforum.com/forums/f13/class-b-ais-units-269595.html
https://avesmarine.com/blog/ais-explanation/

Also, with a raspberry pi onboard graphing the max distance to targets range wil constantly vary with conditions a bit, or a lot when tropospheric ducting kicks in & it can go to hundreds of miles in a few minutes.

Who would have thought it - AIAIS - bit like EIEIO

 

[Sandy]

Elevation ..... how high is your house compared to a boats mast ?

We use AIS to track our vessels not only for voyage but also when doing Ship to Ship transfers ... my guys sitting on one ship calling the other ... "Have you picked up anchor yet - how long before you are here ?" ... often reply is not same as what we see on AIS !! And its rare that we pick up other ship at 50nm ... and that's ships mast heights ... with Class A ... with dedicated antenna's etc.

Thinking about this a bit. I wonder if the quality of the antenna is part of the reason some people have distant targets. I have a VHF Metz running through a splitter.

 

[Refueler]

Thinking about this a bit. I wonder if the quality of the antenna is part of the reason some people have distant targets. I have a VHF Metz running through a splitter.

I would say that the cable used would likely be the greater influence ... along with connectors.

With 25W out of a VHF many people don't worry about the cable and generally use the 'easy to work with' variety. But AIS is at max only 5W ... this then can be affected by what cable used.

I have a no-name antenna that used to be at masthead of my 25 .... then the bracket got damaged on harbour wall when mast was down ... basically I forgot about the 4m of overhang out aft when coming off the town wall ...
At the time ... there was a Forum member who sold Metz antennas and everyone and their dog was claiming great performance ... so I bought one and fitted it. I did not have AIS then ... so I can only post based on VHF use ...
I did not feel I had any more range with it over the no-name unit.
But what I did have was failure of the whip to loaded base of the Metz ... where it had a collet fitting to hold the whip :

I fixed that and its held ... still good today.

The no-name became the pushpit rail antenna ... its base loaded as well but fixed whip.. and cable.