AIS installation

[Offshore Eric]

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

 

[Dellquay13]

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

AIS receive only is easy on the existing antenna using a active splitter. I have an EasyAIS splitter and a quark receiver with Wi-Fi output to a tablet. AIS on a plotter or tablet is much better than on the little vhf screen.

If your VHF is DSC and linked to GPS then there’s no real reason to replace it. If it’s pre DSc then upgrading to DSc with integral gps would be a good step. Going the full upgrade to Vhf with AIS is very expensive for little functionality, unless it can be interfaced to your nav gear.

A little stubby vhf antenna on the pushpit rail just for AIS is also popular if you want to keep your vhf as is. Reduced range on the AIS, but a spare antenna for your vhf should the primary one fail.

Other people swear by Onwa plotters with AIS built in.

 

[Refueler]

I have a passive splitter between my Onwa Plotter with built in AIS Transceiver and the VHF radio ... so both go to the same antenna at top of mast. It works excellently.

There are two forms of splitter :

Passive .. which does not have separate power input to amplify any signals rec'd.

Active ... which has power input to amplify rec'd weak distant signals.

Obviously the Active is the better form, but you pay more for it.

To give an example of the tests I made with my setup ... numbers are averaged :

1. AIS targets received via separate stern rail antenna : ~ 8
2. AIS targets received via mast head antenna without splitter : ~15+
3. AIS targets received via masthead antenna with splitter and VHF : 12+

The difference 1 to 2 + 3 is distance of reception .... the stern rail obviously being low only receives targets relatively close - but is good enough for our use ...
The difference 2 to 3 is due to losses via the splitter for distant weak signals ..... where the ACTIVE will give a boost to compensate ...

AIS unit ? I looked long and hard as to how I was going to install AIS and in the end decided to replace my ancient Lowrance with the ONWA .. the price for Plotter and AIS Transceiver combined at that time was not much more than buying a separate AIS transceiver unit. The advantage of course being that I had AIS targets on screen on the chart ... and ability to connect via NMEA to other units to display AIS ...
My ONWA supplies AIS data to my Garmin UHD .. my Navionics on Tablet and Phone and via WiFi to anyone who sails on my boat.

 

[johnalison]

I have a passive splitter between my Onwa Plotter with built in AIS Transceiver and the VHF radio ... so both go to the same antenna at top of mast. It works excellently.

There are two forms of splitter :

Passive .. which does not have separate power input to amplify any signals rec'd.

Active ... which has power input to amplify rec'd weak distant signals.

Obviously the Active is the better form, but you pay more for it.

To give an example of the tests I made with my setup ... numbers are averaged :

1. AIS targets received via separate stern rail antenna : ~ 8
2. AIS targets received via mast head antenna without splitter : ~15+
3. AIS targets received via masthead antenna with splitter and VHF : 12+

The difference 1 to 2 + 3 is distance of reception .... the stern rail obviously being low only receives targets relatively close - but is good enough for our use ...
The difference 2 to 3 is due to losses via the splitter for distant weak signals ..... where the ACTIVE will give a boost to compensate ...

AIS unit ? I looked long and hard as to how I was going to install AIS and in the end decided to replace my ancient Lowrance with the ONWA .. the price for Plotter and AIS Transceiver combined at that time was not much more than buying a separate AIS transceiver unit. The advantage of course being that I had AIS targets on screen on the chart ... and ability to connect via NMEA to other units to display AIS ...
My ONWA supplies AIS data to my Garmin UHD .. my Navionics on Tablet and Phone and via WiFi to anyone who sails on my boat.

I fitted mine about ten years ago, with a splitter. I haven’t measured the figures but they are in line with yours in that any loss of performance is not noticeable in practice.

 

[Dellquay13]

I have a passive splitter between my Onwa Plotter with built in AIS Transceiver and the VHF radio ... so both go to the same antenna at top of mast. It works excellently.

There are two forms of splitter :

Passive .. which does not have separate power input to amplify any signals rec'd.

Active ... which has power input to amplify rec'd weak distant signals.

Obviously the Active is the better form, but you pay more for it.

To give an example of the tests I made with my setup ... numbers are averaged :

1. AIS targets received via separate stern rail antenna : ~ 8
2. AIS targets received via mast head antenna without splitter : ~15+
3. AIS targets received via masthead antenna with splitter and VHF : 12+

The difference 1 to 2 + 3 is distance of reception .... the stern rail obviously being low only receives targets relatively close - but is good enough for our use ...
The difference 2 to 3 is due to losses via the splitter for distant weak signals ..... where the ACTIVE will give a boost to compensate ...

AIS unit ? I looked long and hard as to how I was going to install AIS and in the end decided to replace my ancient Lowrance with the ONWA .. the price for Plotter and AIS Transceiver combined at that time was not much more than buying a separate AIS transceiver unit. The advantage of course being that I had AIS targets on screen on the chart ... and ability to connect via NMEA to other units to display AIS ...
My ONWA supplies AIS data to my Garmin UHD .. my Navionics on Tablet and Phone and via WiFi to anyone who sails on my boat.

There is a common form of active (powered) splitter which has no gain or boost for weak signals, but it disconnects and protects the AIS receiver when the vhf is transmitting.

 

[Refueler]

There is a common form of active (powered) splitter which has no gain or boost for weak signals, but it disconnects and protects the AIS receiver when the vhf is transmitting.

All Splitters active and passive for AIS + VHF do this protection of AIS receiver .... if they did not - how long do you think AIS unit would survive ?

 

[Baggywrinkle]

There are 2 really useful functions with AIS receive only

.... first is overlay on a chart plotter. You don't say if you have a Chart Plotter or what it is .... an overlay helps see which targets are potential threats and which are not.

... second is DSC calling, which allows you to call a target directly with the VHF

If you have a transponder then other ships will be able to see your position too .... obviously.

So question to the OP ... what do you want from your AIS installation?

I built this into my last boat ...



The AIS came from the SH VHF, so didn't need a splitter .... the data was transferred to the plotter via NMEA0183 and the GPS and AIS Data was transmitted via WiFi by the Yacht Devices WiFi Router to my tablet running Navionics.

Worked very well for about a decade but only got the WiFi upgrade in 2021.

 

[Sandy]

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

If you have the cash buy a transceiver. The VHF sets with AIS screens are difficult to read. Make sure you can display the traffic on your chart plotter. It makes life easier.

If you use the same antenna you will need a splitter, but popping a second antenna on the transom would give you a second antenna should you get dis-masted.

I have a VesperMarine, now taken over by Garmin, and can 'see 50 nm' totally pointless as there are all sorts of course corrections that could happen in the three hours until CPA!

Having the transceiver is useful as:

• you can get called up by name (if only that survey guard ship understood how to do a DSC call!);
• friends and family know where you are;
• the big stuff does look at AIS B
• if they don't the MIAB has lots of evidence should you meet Davey Jones.

 

[MontyMariner]

the big stuff does look at AIS B

Where do you get that from?

 

[Sandy]

Where do you get that from?

By best example is being called up by name in Channel 16 at 0500 in a grey overcast morning in the Firth of Forth, hence the comment that if the OOW understood DSC he would have called me on a bridge to bridge channel.

I have had on watch crew call a ship when they were 'uncomfortable' with their course and CPA, only to be advised that they had already put a 1° course change in and that he should see a change on AIS in a minute or so. My conclusion was they knew we were transmitting on AIS.

In a narrow Thames channel seeing One Manhattan, 153,453 gross tonnes, putting in a 2° course change for three minutes in order to pass me safely. OK - in this example they could have been using a radar plot as this would have been far more up to date, but when something that big puts a course change in, when the channel is tight, you know they are on the ball.

 

[Refueler]

Where do you get that from?

Until about 4yrs ago - I still went on ships to oversee operations. The AIS displayed on ARPA / CAS systems as well as the text only units included Class A and B / B+ ....

The better question is : What makes you think ships AIS receivers don't monitor all three AIS classes ?

 

[Refueler]

Hi Sandy ... 50nm ? That's one hell of a distance for a line of sight unit ... I can accept that for a VHF radio transmission with high enough transmit and receive antennas ... but AIS ? at max 5W for Class A / B+ .... 2W for Class B ??
Yes it can happen with atmospheric conditions - but usually ? 20 - 30nm is good. even on a ship with its much higher masts etc - 50nm would be very good.

Just saying.

 

[johnalison]

Hi Sandy ... 50nm ? That's one hell of a distance for a line of sight unit ... I can accept that for a VHF radio transmission with high enough transmit and receive antennas ... but AIS ? at max 5W for Class A / B+ .... 2W for Class B ??
Yes it can happen with atmospheric conditions - but usually ? 20 - 30nm is good. even on a ship with its much higher masts etc - 50nm would be very good.

Just saying.

It may be an atmospheric effect but 40 miles is not uncommon from my home berth in Essex to around Kent.

 

[Refueler]

It may be an atmospheric effect but 40 miles is not uncommon from my home berth in Essex to around Kent.

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.

 

[Sandy]

Hi Sandy ... 50nm ? That's one hell of a distance for a line of sight unit ... I can accept that for a VHF radio transmission with high enough transmit and receive antennas ... but AIS ? at max 5W for Class A / B+ .... 2W for Class B ??
Yes it can happen with atmospheric conditions - but usually ? 20 - 30nm is good. even on a ship with its much higher masts etc - 50nm would be very good.

Just saying.

I know what you are saying, I have a good understanding of comms stuff, but yes quite often I see ships 50 nm away - confirmed by Marine Traffic - not that I am really bothered at that distance. I am really impressed with VespaMarine kit, just hope now they are part of Garmin they don't mess with it. I suspect VespaMarine have done a lot of work on signal to noise in their kit.

I've also seen a yacht 150 nm off Ushant heading to Southampton on Marine Traffic. I know that was atmospherics as the signal was only seen for about 20 mins. A pal was onboard and returning from the Cuba. It allowed us to get more people to get to the welcome back party.

 

[MontyMariner]

the big stuff does look at AIS B

Sorry Sandy, I had a dyslexic moment and read doesn't!
Ships certainly take note of us little fellows on AIS, but sometimes need a prompt .

 

[MontyMariner]

yes quite often I see ships 50 nm away

Yes, same here, I have my AIS antenna at the top of my mizzen. I did a range test when crossing Biscay and could see ships following the shipping lane which was 50 miles further out.

 

[Jules W]

Mine is on my transom and I regret not having put it up the mizzen. It is fine for big ships and calm seas but it struggles with smaller vessels in a big sea even in as little as 3 miles. They come and go on the display as either we or they are shaded by waves. I would definitely advise putting it as high as you can.

 

[Buck Turgidson]

Transponder with masthead arial through a splitter. I used to get huge range with my old arial but it broke in a storm and the expensive new one fitted professionally is nowhere near as good. This clip is with the old one at 2200 ish in the MED. Just look how well populated the screen is and how useful a tool it is. (spoofing and dark targets aside)
AIS

 

[Sandy]

Sorry Sandy, I had a dyslexic moment and read doesn't!
Ships certainly take note of us little fellows on AIS, but sometimes need a prompt .

No worries, I have them all the time. I put it down to age.