Please select your home edition
Edition
Mackay Boats

AIS-One Cruiser's Experience- Part 2, Installation

by Neil Langford on 14 Oct 2008
Display showing our boat and ships .. .
Pictured above is the screen as it works on the AIS (Automatic Identification System). The system is now the world-wide accepted active primary safety system for vessels at sea. The black arrow at right of the photo, captured from our PC screen, is our yacht Crystal Blues. The red arrows (targets) are ships we want to avoid. Clicking on a target reveals the data box seen at bottom left - lots of information on the ship in question.

I met a cruising sailor last night who said that my first AIS story was very technical - oops, I guess it is a technical subject. Not sure that I can eliminate the technicalities, but I will try to explain them. First though, an essential technology primer .... I strongly recommend you spend time roaming the excellent PANBO website, specially the AIS pages. Also, here are links for two very informative and useful documents, covering co-axial connectors and co-axial cabling. OK, on with the story ....

We purchased our Class B AIS transponder from Oceantalk in Singapore - in fact we bought four of them, as several other boats wanted to install the system. The unit is a Comar CSB.200, manufactured in the United Kingdom. It was supplied by Oceantalk with a Shakespeare VHF whip antenna and a Sanav GPS antenna.

All Class B AIS transponders require a dedicated GPS receiver and a dedicated VHF antenna. No arguments please - if you want this powerful safety system, you have to install the extra antennae. No, you cannot share signals from existing systems, however the AIS derived GPS position information is available to you as a separate NMEA signal, for chart plotting purposes. You'd better plan carefully for antenna locations, bracket positions and cable runs.

The GPS antenna is a simple patch antenna with a low noise amplifier that sends the received signals (as RF) direct to the AIS system for timing analysis - in other words, the external receiver is just an amplified antenna, and all the complex decoding and mathematical computations to derive your vessel position occur inside the AIS transponder. This is a specific requirement of the IMO AIS regulatory framework - it basically ensures that no one can feed fake vessel positions into the system. That is good to know ...

On the VHF side, AIS Class B uses just 2 watts of radiated power to send its reports outwards (the big ships get 12 watts). It is easy to receive signals from big-ship class A systems, however you better pay attention when installing your VHF cables, connectors and antenna. You want to ensure that all of your 2 watts is actually radiated into the ether. Robin Kidd from

Oceantalk stressed this point - make sure your VHF cabling and connection work is good. Installation requires the following :

- Physically mount the AIS box. A U-bracket is supplied, but we used industrial strength adhesive Velcro to mount it on a vertical bulkhead (see photo).
- Run the cables for VHF and GPS antennae
- Install and connect both antennae
- Run cable for DC power with a fuse in line
- Run the data cable to the chart plotter/display system
- Terminate everything and then commission the system

Of course your chart plotter must be compatible with AIS messages in NMEA format to display the targets and information. If it isn't, you can use this very neat AIS display from Vesper Marine, the AIS Watchmate, or a more serious display (with charts) made by Comar, the CSD.200.

Back to the installation. If you power the box from a shared DC circuit breaker (ours is on our navigation instruments circuit) you should include a 5amp fuse in the power feed. Be careful with the VHF antenna cabling - OK, its just RG.58, but you've only got 2 watts to radiate, so make sure you use high quality connectors and fittings.

The GPS receiver supplied by Oceantalk is the RV-76, made by San Hose Technology in Taiwan. It includes a nice 10 metre pre-terminated cable. Its very thin, and easy to run through the boat, but it turns out to be RG.174, which has very high losses (attenuation) at these frequencies (1.5ghz). If you use the supplied cable as-is, with its existing terminations, it will work just fine. However if you need to cut, join, extend or splice (as we did), then you'll have to use a more suitable cable (RG.223). After attempting to extend the supplied cable, and getting no satellite signal, we changed to a Bedea RG.223 with Telegartner crimp connectors - voila, tons of signal. We purchased the cable and connectors from Coastal Electronics in Singapore, though similar cable is made by Belden and others. Make sure you use the correct crimping tool (see photo).

On the VHF side, the Comar AIS box will actually measure and report the SWR (reflected energy ratio) on your VHF transmission line during commissioning - you'll soon know if your VHF cabling and connectors are good or not. Click on the photo below at right to see typical values.

With all that hard work done the rest was easy - plug the box into our PC using the supplied cable and configure the COM port on the PC (baud rate etc) . Then load the Comar software (supplied) and configure the unit. At this point you'll be asked to input your vessel identifier, which is the unique 'MMSI number' issued by your National Marine Authority. If you don't have an MMSI number you'd better apply for one now, because you cannot transmit using AIS without one. A Comar Class B transponder will stay in 'receive only' mode until you give it your MMSI number. The real trick is that this number can only be entered ONCE by the user - mess it up and you have to send the box back to the dealer for resetting.

I've just learned that Class B systems are FINALLY approved for use in the USA (story here), but that they are not allowing users to configure the MMSI identifiers. I bet that will be fun to administer.... seems the installers or retailers will have to configure the box before handover. The Comar configuration software is simple to use, neat and logical.

So, use only good cables and connectors, get yourself an MMSI number and enjoy the results. Our next story on AIS will conclude the series with our user experiences.


To read more about the adventures and exploits of Neil and Ley on Crystal Blues, go to their website

Zhik Yachting 660x82Ancasta Ker 33 660x82Protector - 660 x 82

Related Articles

America's Cup - Oracle picks up some bow protection for docking
Bangin' the Corner team talk Jimmy and the boys on Oracle Team USA through the process of getting some bow protection The Bangin' the Corner team talk Jimmy and the boys on Oracle Team USA through the process of getting some bow protection for their new AC50, before they dock after a long day on the Great Sound, and don't dock like Ben did.
Posted on 25 Mar
Bureau Vallée 2 back in the water in Brittany
The former Banque Populaire VIII aboard which Armel Le Cléac’h won the last Vendée Globe was put back in the water The former Banque Populaire VIII aboard which Armel Le Cléac’h won the last Vendée Globe was put back in the water on Friday in Lorient (Brittany), with her new decoration in the colours of Bureau Vallée.
Posted on 25 Mar
America's Cup - Bermuda practice racing videos March 24, 2017
MyislandhomeBDA is videoing the Practice racing and training with the five teams in Bermuda MyislandhomeBDA is videoing the Practice racing and training with the five teams who are based in the venue for the 2017 America's Cup. Here's the set from March 24,2017
Posted on 25 Mar
America's Cup - Coutts hits back at critics over Protocol change
Russell Coutts, has responded to criticism over the recent changes to the 35th America's Cup Protocol Five times America's Cup winner and CEO of the America's Cup Events Authority, Russell Coutts, has responded to criticism over the recent changes to the 35th America's Cup Protocol, allowing testing and racing between Challengers and the Defender in Bermuda ahead of the start of the Qualifiers.
Posted on 24 Mar
America's Cup - Groupama Team France's AC50 sailing in Bermuda - Video
Groupama Team France has had her first sail in Bermuda with the AC50 looking impressive in the video shot by the team. Groupama Team France has had her first sail in Bermuda with the AC50 looking impressive in the video shot by the team.
Posted on 24 Mar
America's Cup - Images of Emirates Team NZ flypast Devonport
Image gallery shot as Emirates Team New Zealand returned in the late afternoon from another four hour race session Image gallery shot as Emirates Team New Zealand returned in the late afternoon from another four hour race training session on the Waitemata harbour. Our cameras were on Devonport Wharf to catch the sequence - and for the first time a wide angle lens had to be used.
Posted on 23 Mar
America's Cup – Get to know Iain Murray and the ACRM
He has enjoyed a long and illustrious career since he first started sailing at the age of nine in his native Sydney. Throughout its 166 year history the rivalries between owners, skippers, crews, yacht clubs, fans and nations have been some of the most intriguing facets of the competition for the world’s oldest sporting trophy.
Posted on 23 Mar
America's Cup - Images of Emirates Team NZ two-up on the Waitemata
Emirates Team NZ were sailing on the Waitemata yesterday with just a couple of weeks left Emirates Team NZ were sailing on the Waitemata yesterday with just a couple of weeks left before they head for Bermuda and the 35th America's Cup. The cycle-grinders were two per side for the trip down the harbour making the transitions from gybe to gybe very interesting - and almost imperceptible.
Posted on 23 Mar
America's Cup - Late Protocol change further stacks deck against Kiwis
Five America's Cup teams have dealt themselves a new hand with a new Protocol Change published three days ago. Five America's Cup teams have dealt themselves a new hand with a new Protocol Change published three days ago. On the face of it, the change - to allow 23 days training against each other repairs an omission by the Commissioner for the America's Cup. But it is the timing of the move that is surprising
Posted on 22 Mar
Vestas 11th Hour Racing launch Volvo Ocean Race campaign
Vestas are returning for a second edition, after launching their 2017-18 campaign in partnership with 11th Hour Racing Vestas 11th Hour Racing will be led by the American duo of Charlie Enright and Mark Towill. The team are the fourth to announce for the upcoming edition, which begins on 22 October, and they will use the race to promote a sustainability message around the world.
Posted on 21 Mar