Choosing & Using AIS
In the 15 years since the marine AIS (Automatic Identification System) was introduced, many thousands of AIS receivers and transceivers have been sold for yacht installations. AIS is a method of tracking other vessels using a receiver or transceiver operating on the dedicated marine VHF Channels 87B (161.975MHz) and 88B (162.025MHz). Because of the considerable safety benefits offered by this technology, Class A AIS is mandatory for all SOLAS vessels over 300 tons. Class A or less powerful and less expensive Class B AIS is also mandatory on many smaller and/or more local commercial vessels, and either can be used by recreational vessels.
Receiver or transceiver?
For around $150 you can purchase a budget AIS receiver that will track AIS equipped vessels operating within VHF range (up to 30nm mostly depending on antenna height) and overlay them onto an electronic navigation chart. Some receivers offer an alternate radar-style AIS target display.
Most sailors rightly consider it important for their own vessel to be visible to others, rather than just being able to see others around them. This requires the installation of an AIS transceiver along with its own GPS and AIS antennas (or VHF antenna splitter).
By design and regulation, a Class B AIS transceiver determines its position, speed and course using its own GPS receiver. This information may then be combined with Heading and is then automatically transmitted to AIS-equipped vessels within range. Most Class B transceivers can feed the GPS data into your PC or chart plotter via an NMEA output, but the feed is usually quite filtered.
Some AIS units are supplied with an external antenna, but with some models, they are an optional extra, so when pricing a system make sure to add this item if necessary. Some units have an internal GPS antenna as well, although you’ll need to consider where the device is installed to ensure the best reception.
Some GPS antennas come with a mini-FME plug on the end; others have a full-size BNC connector. If you want to keep hole sizes to a minimum when installing or need to poke the GPS cable down a narrow conduit, then the smaller the connector the better as the manufacturers all warn against cutting the cable.
If you wish to use your existing VHF antenna for both your AIS and VHF radio you’ll need an antenna splitter. AIS receivers only require a simple passive antenna splitter, but a Class B transceiver needs a more expensive “active” splitter that isolates the two when the VHF is transmitting. If not built into the transceiver, an active splitter usually costs around $200 and also be aware that your Class B AIS will not complete its position update—normally broadcast every 30 seconds when underway—if you’re talking on the VHF at the same time.
All AIS units have at least an NMEA0183 output for direct connection to compatible AIS target plotting devices such as chart plotters and MFDs. Many now also have an NMEA2000 port for more easily connecting to such a display or a network of them. Few makers seem to supply the necessary drop cable and T-connector for N2K networking, however, so that should also be considered in the budget if required. Just these two items alone can cost $50 or so.
In the U.S., Class B AIS transponders are sold with your MMSI number, boat name and other details already programmed. But if you’re planning to fully self-install or want to change any details except the MMSI, be aware that the most common problems with PC setup programs like proAIS are setting the COM port correctly on the laptop and/or getting the USB device driver to load. You may need to manually install a driver supplied on a CD or found on the Web.
Configuration and logging software
The PC configuration software usually provided on a CD not only enables you to configure the AIS with your MMSI (outside the U.S.) and boat details but also allows you to diagnose problems, check the GPS reception, list the nearby AIS vessels and finally log the received NMEA signal.
ProAIS2 was the most common control program encountered and it’s simple to use despite containing very comprehensive features.
Choosing a Transceiver
I have reviewed a number of AIS transceivers. Here is a quick guide to some of the most popular units on the market. New units are constantly being introduced so this does not claim to be a comprehensive list.
ACR AISLink CB1
This neat little unit boasts an integral 50-channel GPS receiver with its own internal antenna, but it still has a BNC connector for an external GPS antenna if preferred. ACR doesn’t appear to supply its own-brand antenna splitter, but there are plenty of others available.
The AISLink is simple to install, as all the connectors are at the bottom of the box and there are four status LEDs on the front. The indicators remain amber until you have entered your MMSI via the proAIS2 program, after which the green light indicates that all is well and the unit is transmitting and receiving.
This is a smart and compact unit that has everything other than flash card logging. It is simple to configure and comes with a comprehensive manual and the proAIS2 software on a CD. acrartex.com
There are two models of this compact transponder—the 108W is identical to the 108, only with Wi-Fi. Both have a full-size SD card slot that enables you to record a log without being permanently attached to a PC.
The Camino is about the same size as the McMurdo and the AISLink, with antenna connectors on the top and USB, N2K and power/NMEA-0183 at the bottom. The SD slot is under a waterproof flap on the front. Also on the front are LEDs for power, error, Rx, Tx/silent, SD and Wi-Fi (108W). milltechmarine.com
This model has been around for quite a few years and is starting to look and feel dated. The BNC antenna connector requires a converter from the more standard PL259 plug usually found on a marine VHF antenna. Comar also produces an active antenna splitter (AST200) that comes with all the necessary cables.
The AIS uses proAIS software, which is supplied on a CD, along with the operating manual. comarsystems.com
Digital Yacht AIT1500/2000/3000
The entry-level AIT1500 has limited features, including internal GPS antenna only, NMEA-0183 and USB data ports, a BNC antenna connector, and four status LEDs.
The AIT2000 offers NMEA-2000 multiplexing and a 50-channel high-speed GPS receiver with external antenna. Those wishing to keep separate AIS and radio antennas can order the 2000 with a GV30 AIS/GPS combination antenna and for Wi-Fi output to phones and tablets you can add the WLN10HS Wi-Fi server. Consider the AIT3000 if you like to have VHF/AIS splitter and Wi-Fi built in. The transponders are quick and easy to install and used all the facilities of the proAIS2 software, including logging. The GPS signal on the AIT1500 wasn’t strong below decks, though, so we would recommend the 2000 or 3000 models with the external GPS antenna. digitalyacht.com
This unit is fairly large, but comes with a built-in antenna splitter, thus making it smaller overall than two separate boxes. Designed for bulkhead mounting, available ports are GPS antenna, SRM (safety-related messages), USB for PC configuration and diagnostics, power/NMEA-0183 and NMEA-2000.
Although the Garmin might seem expensive initially, it appears good value if you need the antenna splitter, external GPS antenna and NMEA-2000 compatibility. garmin.com
This was the only unit we tried that has its own display, albeit quite small (4in). The output can be connected to a compatible chart plotter via its NMEA-0183 port, which is on a 15-pin mini-D connector. A plug and cable are provided, though, as is the external GPS antenna.
Using the display you can toggle between three primary pages—Plotter (with selectable vessel detail), Target List and Danger List. The Plotter page looks similar to radar, with North/Course-up and 0.125-24nm ranges. The Target List shows all detected AIS targets and the Danger List shows vessels with a CPA of 6nm or TCPA of one hour.
Configuration is done via the display as it doesn’t have a USB port. The only way to log AIS events on a PC is to use an RS232/USB converter on the NMEA-0183 output. If you have an Icom VHF you can connect it up and make individual DSC calls directly from the MA-500TR. icomamerica.com
McMurdo SmartFind M10
Small and neat, the SmartFind M10 somehow manages to squeeze in a GPS receiver and USB, NMEA-0183 and NMEA-2000 ports, as well as an SD card slot that can be used for data logging without the need for a permanent connection to a PC. The M10W Wi-Fi version also allows connection to smartphones and tablets.
The VHF and GPS antennas supplied connect to the top, while the other ports are at the bottom and the SD card slot under a rubberised cover on the front. A row of status LEDs shows Power, Error, Rx, Tx and SD.
The unit comes with a CD containing the configuration software and an AIS viewer program that can be used when the USB lead is connected to your PC/laptop, giving you a second large display of AIS targets and the ability to log vessel movements. mcmurdomarine.com
A small, well-sealed box with VHF and GPS antenna, Power/NMEA-0183 connector and STng ports on the bottom. Under a plastic cover on the front is a mini-USB2 port and full-size SD card slot. A single LED on the front shines different colours depending on the status—green (good), amber (waiting), blue (silent) or red (error). Fine if you happen to have the manual handy!
The AIS650 has a built-in 50-channel GPS receiver and silent mode can be enabled directly by many Raymarine displays. Being Raymarine it has a SeaTalk connector rather than standard NMEA-2000, so you need an adapter cable to join a regular N2K network. We feel this should have been included, along with a USB cable, which is essential for the initial configuration.
A copy of proAIS2 is supplied on a CD, along with other documentation. The SD card slot is for software updates and data logging only. raymarine.com
Fully waterproof and compact, this AIS is designed to bulkhead mount and has connectors for the VHF and GPS antennas on the top and the data ports, including NMEA-0183, NMEA-2000, USB, together with the power at the bottom.
With a 50-channel high-speed GPS receiver built in and a GPS antenna supplied, you can be up and running in no time after downloading the proAIS2 software supplied on disk.
The NAIS-400, like many of these AIS devices, can multiplex Heading or similar data coming into its 4,800 baud NMEA-0183 port with the AIS data going out of its 38,400 High Speed 0183 port to a chartplotter or via USB to a PC.
Simrad (part of the Navico group) also produces an active antenna splitter using an identical system. simrad-yachting.com
Vesper Marine is an Auckland, New Zealand-based company completely focused on AIS, especially for sailors. Although this review did not get into the tricky business of AIS alarming, Vesper’s various WatchMate displays are very sophisticated in this regard. What we explored are Vesper’s two XB black box AIS transponders—the 6000 and the Wi-Fi-enabled 8000. The fully waterproof XBs are compact and have an internal GPS receiver and antenna, so in some installations, the external GPS antenna (supplied) might not be needed. Ports include NMEA-0183/2000, USB, GPS and VHF antenna, all of which face downwards for a neat installation. A single LED status indicator varies in colour and flashes to signify a wide range of conditions.
Both models use a high-speed, 50-channel (5Hz) GPS, and are uniquely able to stream GPS data over their N2K port that’s detailed enough that most chartplotters accept it as valid. The units also multiplex many common NMEA-0183 and N2K instrument values like depth and wind over their N2K and USB streams, as well as over Wi-Fi for the 8000. Plus the 8000 can trigger an external alarm based on an AIS MoB signal or an anchor watch set up with its associated Vesper app. No CD of software or drivers is supplied, you need to go online to download these onto your laptop before you can configure and initialise the unit. vespermarine.com
AIS transceiver specifications are highly regulated and, in fact, many the devices above use very similar electronics built by the UK specialist company SRT so the choice comes down to install details, what’s provided in the box, extra features or perhaps the advantage of having all tech calls going to one brand. An app configured anchor alarm, onboard logging to data card, easy silent mode switching, and/or NMEA-2000 output may be important to your situation. Built-in Wi-Fi is handy for sending AIS and GPS info to apps, and even more useful when the transponder also multiplexes in lots of useful instrument data.
You need to decide whether you want an antenna splitter or not. If not, then rule out those with an in-built splitter and save the money for the new antenna installation. If you do, then it’s worth looking at one with the splitter included, such as the Garmin AIS600 and DY AIT3000, or even Icom’s MA500TR, which also gives you an AIS display. (Having a small zoomed out AIS display often works well with a zoomed in nav screen that also shows AIS targets.) While all come with the GPS receiver circuitry built-in, most require an external GPS antenna. A few have an internal antenna (AIT1500, Vesper XB, AISLink), but I’d be wary of relying on it below deck.
All modern AIS transceivers offer a silent mode in which AIS transmissions can be halted. This feature is considered essential for those who cruise in areas where piracy might prove it sensible not to broadcast your position and details to nearby vessels.
Silent mode can be activated using a software switch if you have a laptop connected; some transceivers have a hardware button; many offer a pair of wires that can be connected to a remote switch; and at least Raymarine can “Silent” its AIS via an MFD or instrument display setting.
Other AIS transmitters
Recent developments in the AIS field include the introduction of AtoN (Aid to Navigation) beacons. An AtoN beacon can be Real (ie. a transmitter installed on a buoy or lighthouse etc), Virtual (simply an AIS signal transmission sent from a land station containing the position data of the ‘mark’), or Synthetic (a virtual style transmission over an actual physical AtoN). Another icon commonly seen these days (well, hopefully not too often) is an MOB icon, which is transmitted by a personal AIS distress beacon. All Class B AIS devices receive this information, but not all chartplotters know how to present it properly. An AIS MOB, for instance, may look like a vessel and in some cases AIS AtoNs are not displayed at all.
When he’s not testing electronics and sailing equipment, Duncan Kent is sailing somewhere in the English Channel