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New Type of Class B+ AIS Transponders at METS 2018

The UK based company Digital Yacht will introduce a new range of Class B+ AIS transponders at METS 2018.


Class B+ is a new AIS standard. This is performance similar to Class A transponder but for non mandated users. This new standard is ideal for ocean sailors requiring the best possible performance and future proof satellite tracking applications, fast power boats and smaller non-mandated commercial vessels. It still inter-operates with existing Class A and Class B systems.

  • It utilises SOTDMA format transmissions which offer a 5W power output (2.5x more powerful than a regular Class B)
  • A guaranteed time slot for transmission in busy traffic areas
  • Faster update rates depending upon the speed of the vessel

There are two models. The AIT2500 is priced at £575/€745 and the AIT5000 at £875/€1050, which has a patented ZeroLoss VHF-AIS antenna splitter allowing the main VHF antenna to be shared with VHF and AIS.

Both models incorporate:

  • Full function transponder with NMEA 0183, NMEA 2000 and USB data outputs
  • A wireless interface for connecting to iPads and tablets
  • AIS SART alarm which is great for use with personal AIS MOB devices
  • Compatible with the Digital Yacht iAIS app which is Navionics enabled too, allowing AIS targets to be overlaid onto the popular Navionics iPhone and iPad charting

For more information go to www.digitalyacht.co.uk or www.digitalyacht.eu.com


Digital Yacht AIT3000 “Nucleus” Class B AIS transponder debuts at Southampton Boatshow


DY NucleusDigital Yacht have launched an interesting hybrid product. Combining Class B AIS transponder with built in antenna splitter and WiFi interface to support Apple and Android tablets and phones.

Class B AIS transponders have made a big impact on small craft navigation, but many potential users or installers are put off by the requirement for yet another VHF antenna.

The new AIT3000 “Nucleus” from Digital Yacht changes that perception as it incorporates not only a full function Class B AIS transponder but also an antenna splitter allowing the main VHF antenna on the boat to be shared with the AIS and VHF. 

Digital Yacht have coined the name Nucleus because it can also become a hub for on board navigation.


It has been designed with an interesting number of interfacing capabilities including :

  • ZeroLossTM technology for the antenna sharing
  • NMEA 0183, NMEA 2000
  • USB port
  • WiFi server so that NMEA data from other on board systems can also be multiplexed by the Nucleus and combined on the WiFi link
  • Apple IOS and Android support.
  • FM Stereo output


Digital Yacht also offer a free AIS viewing app called iAIS as well as more sophisticated charting apps like NavLink. If you’re an Android user, AISView is also compatible. 

The NMEA interface allows connection to any AIS compatible chart plotter and USB is available for MAC or PC user as well as allowing programming of the unit with your boat details.

Other features include a silence switch option allowing the unit’s transmissions to be stopped while continuing to receive AIS transmissions.  


Why is AIS important..

Almost every cruising boater knows about AIS – the Automatic Identification System. Released in the last 10 years, AIS-A became standard on large ships. Today it is a required piece of equipment on most large commercial vessels. However, AIS-A was fairly expensive and complex, so few recreational boats installed it.

AIS works through VHF radio. Packets of data are sent out providing live navigation data – position, speed, course, heading – along with other very useful information – vessel name, vessel dimensions, MMSI, age of data, etc.

Early devices for cruising boats were only receivers. They'd allow your chartplotter or PC navigation software to view the position of ships broadcasting AIS packets. For offshore, busy harbors, or twisty rivers, it gave a view of the ships that were coming in many cases when radar didn't give enough information. It also provided automatic collision detection and warnings.

In 2007 AIS-B was released with a lower-cost set of specifications to work alongside AIS-A. Still, early AIS-B transponders were over $1,000.

A transponder not only receives all AIS traffic for display but also sends out information about your boat for others with AIS including ships. Over time transponder prices dropped and capabilities increased to the point where today you can purchase a full AIS-B transponder for far less. Between these new prices, the ease of integration, and the support of AIS in almost every chartplotter and navigation software, we think that if you don't have an AIS transponder, now is the time to get one.

We've had AIS integrated into our electronics since February. It didn't take long before we saw how useful it was.

Here are some examples of how we really use it:

  • AIS targets show a ship's or boat's name. That is very useful when you want to communicate with them especially at night.
  • When a boat is coming from behind, the AIS target and track line generally gets our attention. Our 7.5 kt speed means we're passed a lot. It's very nice to see the speed and closest approach calculation as a faster boat is approaching.
  • In a specific situation involving a barge, an American Cruise Lines ship, and narrow cuts, we were able to see them miles in advance on the ICW. This allowed us to hail them by name and arrange for a safe passing location. Time to closest point of approach is one of the standard AIS displays presented allowing you to see approximately how long it will be before you meet oncoming traffic.
  • Finding friends nearby by seeing their boat name is a great social tool. It's also nice to see the names of boats you're traveling with on your display.
  • Transmission of a ship's MMSI allows for VHF DSC radio calls to boats that are unknown to you. This is quite valuable for offshore communication with ships especially at night.

When looking for an AIS-B transponder, make sure it has an integrated GPS, has low power requirements (2-5 watts), and has connectivity to the displays you need. Typical devices will have NMEA 183, NMEA 2000, or USB. A device that has all will provide the greatest use no matter what other navigation products you use now or might switch to later.

If you're using PC navigation software, a USB capability is very nice since no adapters will be needed – just plug the USB cable into the PC.

There are some AIS devices with WiFi. We think these devices are too limited and create difficult situations. They limit connectivity to a single display and often make it difficult to use other WiFi systems in your boat at the same time. There are better ways to integrate NMEA 2000 with WiFi that we'll write about in another newsletter.

Suffice it to say, NMEA 2000 on any AIS device you purchase should be a requirement because it'll give you many future options.

If you don't currently have an AIS transponder, you've probably been thinking about getting one. It's time. Get it now and use it over this next cruising season. You'll love it and wonder how you got along without it.

AIS – Complexities and Issues

There are a couple of things to keep in mind when planning an AIS installation:

  • The transponder needs a VHF antenna. There are two ways to install this.

1) Get a small, inexpensive VHF antenna and install it, or

2) use a VHF splitter which will allow you to share an existing VHF antenna with the AIS radio. A good splitter will cost a couple of hundred dollars and requires power but often makes the installation simpler. The decision for a splitter isn't simple – you probably have multiple VHF antennas already. If you don't, consider an inexpensive VHF whip antenna. We used a splitter with our secondary flybridge VHF antenna.

  • The transponder is supposed to have its own GPS. For maximum quality of signal, make sure the AIS unit is placed in a location that will have a good, reliable signal. If you must buy an AIS with an integrated GPS, make sure to get an external antenna for the GPS part and put that antenna someplace higher. The GPS for our AIS is in our pilothouse ceiling with fiberglass above it. We do not have a GPS antenna outside but the inside location works perfectly. We made sure to test the GPS signal strength before finishing the installation and were prepared to modify the location if needed.

There are also a few complaints and issues we've heard about AIS. Below are our opinions on these:

Issue 1. If everyone has AIS, it's going to get too crowded, and the AIS alarms will go off continuously.

We believe that people who experience alarms going off all the time aren't using their AIS capabilities properly. When inshore and in high traffic areas, there is little need to have alarms enabled for AIS. In most cases, you're watching the navigation system carefully and will have visual AIS warnings of approaching vessels. Most systems allow AIS targets to be removed from targeting as well. Only when you're offshore or in a non-crowded area should AIS alarms be turned on. Electronic navigation means using your electronics – you can't expect to set it once for all types of travel and forget about it.

Issue 2. I don't want others to see who I am.

We believe this is compromising your own safety. It is much safer to receive a VHF call with your boat's name rather than a lat/lon estimate.

If you do feel a need for secrecy, most AIS devices have a switch that will turn off the transmission of your data. We didn't even install the switch on our AIS because we believe it's a bad idea to turn off data transmission.

Issue 3. Ships just turn off AIS-B traffic so having a transponder is worthless.

First, we don't believe it is true that ships can turn off AIS-B traffic.

We'd love to know from ship pilots out there and we'll get the info out.

In our experience, every ship we've called said they could see our boat on AIS and our name on their displays. That's good enough for us. But we'll keep asking.

There are many other capabilities possible and coming with AIS. There are already inexpensive wearable AIS transmitters for crew. Fall overboard and the person in distress becomes an AIS target on all chartplotters in the area.

Virtual buoys are being experimented with by the Coast Guard. If there's shoaling or a missing buoy in the future, it's likely to be a radio signal with a lat/lon that will show up at the proper position on your AIS display.


By Jeff Seigel

Guest Author & Founder of ActiveCaptain



5in. All in one chart plotter + AIS receiver for less than £500!

SC500_00The Digital Yacht SC500A GPS Chart Plotter with built in AIS Receiver is really the sort of thing that the ill fated Raymarine RC400 could have evolved into.

To be fair I have used the RC400 mounted at the helm of my 32ft yacht, and despite all its faults and initial hiccups in getting it to work at all I must say that it has withstood both hell and high water and worked very well for the past 4 years. The trouble is that it doesn’t link to anything and connecting it to PC based chart plotting/planning software is useless- er, yes I do know about RNS…!

So the Digital Yacht range of 5” colour chart plotters caught my eye especially when you see some of the sophisticated things it can do.

Firstly it is a modern device unlike my poor old RC400 and benefits from all the technical hardware innovations of the past 5 years – for example there is an ultra bright display with 256 colours and a resolution of 320 x 240 pixels.

The unit also uses the C-Map cartography which means that you get all of the following features…

5in. All in one chart plotter + AIS receiver for less than £500! → Click here to continue reading →


Buy Raymarine AIS500 or buy £800 of Raymarine shares?

AIS500 I applaud Raymarine for having brought this unit out earlier this year, it is good product marketing and market positioning (pun intended:-)

But if you already have a reasonably sophisticated set up, and already have AIS, is it worth spending £800+ to upgrade to this unit?

Here is my take on the list of features for the AIS500:

Feature Comment
* Class B AIS Receive & Transmit Good – and so do all the competition at this level
* Dual Channel AIS Monitoring Ability Good – and so do all the competition at this level
* Targets displayed on chart and radar screens Clever – but I normally overlay radar on the chart plotter or display AIS targets on the chart rather than the radar which could be very confusing if not misleading due to the different methods of target acquisition
* LED Status Indicator Good – Surprising omission on so many marine electronics and very annoying when there is no status light and you are troubleshooting.
See my posting here on the RaymarineAIS250
* NMEA 0183 – Compatibility with Raymarine A, C, E and G Series Good – the great majority of Raymarine users must be on C series (or lower) still.
* Buddy Tracking via Raymarine MFD – Distinguish favourite targets (MMSIs) from others by adding to favourite list Clever – but is this really needed – oh ok could stave off boredom in some situations to switch between “favourites” and “all” targets. In between calling your buddy on the radio…
* Silent Mode – Turn off transmit function during tournaments or races if you do not wish to be seen. Good – But only if you expect to be sailing in regions where piracy is possible – not really a problem in the Solent – yet!
I did refer to this as a good thing in my posting here:-)
* Built-in NMEA multiplexor Not Good – I have a principle of using separate dedicated pieces of electronics instead of multifunction devices ion this situation. A faulty multiplexor can take down the whole backbone and all links between devices I would not want to troubleshoot that with a device that was doing so much else as well.
See my posting here on multiplexors.
* VHF Splitter – No need to buy a separate antenna. Utilize your existing VHF antenna and cable. Not good – don’t use splitters on your VHF cable!. keep the radio and its aerial as separate as possible. Yes I know that DSC has meant connecting the VHF to the NMEA circuit – but just don’t mess with the VHF aerial. This is a critical lifeline. Install a separate VHF aerial for AIS on the pushpit IMHO.
* Includes dedicated external GPS antenna (16 channels) Not good – as per comment above. Keep the GPS separate, you probably already have one, get another one for backup don’t get one built in to another multifunction device.
* Configure via PC Software
* Software upgradeable through PC and RS232
Ok – but why use serial connections and then very probably a serial to USB convertor when you can use high speed USB. Most modern laptops don’t even have serial ports
See my posting here on serial / USB convertors

I last did a quick survey of transponders (or are they transceivers) in June 2008, but I have held off updating this since I believe that we can expect another revolution in AIS for small boats in the next 6 months.

On that basis I would not buy the AIS500 now, if you already have AIS – if you don?t – then it is a very capable unit with the benefit of a back up GPS.

If you already have AIS and you want to spend £800 buy Raymarine shares, if you made 30% profit when Garmin buy them, that would be an extra £240 to spend on the next generation AIS – then again shares can go down as well as up:-)