VHF Antenna Options for AIS

Splitter v Antennas

One of the most common questions we are asked by our AIS customers, is “what antenna should I use for my AIS ?”, so we thought we would post a short article to provide an answer.

Basically there are two options; fit a second dedicated VHF antenna a suitable distance from the vessels main VHF antenna or use the main antenna for both VHF and AIS by fitting a special device called a “Splitter”.

Generally our recommendation for yacht owners who want to fit an AIS, is to use a “Zero Loss” splitter like our SPL2000. By utilising the main VHF antenna at the top of the mast, you will definitely get maximum transmit range, plus the ease of installation often makes it a cheaper option than paying for a second antenna to be installed.

However, for power boaters who do not benefit from the height advantage of using the main antenna at the top of the mast and for AIS receiver owners where the splitter can often cost more than the AIS receiver itself, it is often desirable to fit a second VHF antenna, particularly if you intend to save money by doing the antenna installation yourself.

We have already covered the issue of AIS antenna separation in another post, so we will not repeat this information again, but we will just touch on the issue of “AIS Tuned” antennas versus normal VHF antennas.

AIS operates on two dedicated channels within the marine VHF frequency range – 156.0 to 162.025 MHz. The two AIS channels are at the top end of this range namely; 161.975 and 162.025 MHz (channels 87B and 88B). Most VHF antennas are designed to give maximum gain across the whole VHF frequency range centred on Channel 16 (156.8 MHz).

Pretty much all of the antenna manufacturers now produce “AIS Tuned” antennas, which have their centre frequency shifted from Channel 16 to 162Mhz (exactly half way between the two AIS frequencies). If you are going to mount your AIS antenna on the stern rail of a yacht or radar arch of a power boat, then using an “AIS tuned” antenna to get an extra bit of gain to compensate for the antenna being effectively at deck level, is a good idea.

AIS Tuned Antenna Graph

The graph above shows how the tuning of the antenna to 162MHz gives it an extra boost in VSWR (gain) across the two AIS frequencies.

Which ever option you choose, having AIS on your boat will without doubt make your sailing experiences safer and less stressful in poor visibility or when crossing busy shipping lanes. Even a simple receiver with a small whip antenna at deck level will keep you informed of what ships are around you and which ones you need to keep an eye on.

Connecting our new AISnode receiver to a Simrad Network

Simrad NSE NMEA2000 + AISnode


Our new AISnode receiver for NMEA2000 networks will work with any AIS compatible chart plotter connected to an NMEA2000 network.

In a previous post we showed how the AISnode could connect to a Raymarine network and in this post we are focusing on Simrad NMEA2000 networks. Simrad adopted their own proprietary connector system for NMEA2000 (SimNet) and so connection of our AISnode will require a SimNet to NMEA2000 adaptor cable (Simrad P/No 24006199).

Once you have the SimNet to NMEA2000 adaptor cable, connect this to the standard NMEA2000 cable that is included with our AISnode and then find a spare SimNet connection on the network to plug the adaptor cable in to. The AISnode will then take its power from the SimNet network and send all received AIS data on to the network.

All of Simrad’s NSS, NSE and NSO chart plotters support AIS and as long as the chart plotter(s) have the latest firmware (free download from the Simrad website) then you will see all of the different types of AIS targets, including the new AIS Man Over Board systems and AIS AtonNs (nav-aids).

It should be noted that all of the latest B&G Zeus Chart Plotters also use SimNet network connectors and so our AISnode will work with these chart plotters in the same way.

For more information on our AISnode, please click here.

Connecting our new AISnode receiver to a Garmin Network

Garmin NMEA2000 + AISNode

Our new AISnode receiver for NMEA2000 networks will work with any AIS compatible chart plotter connected to an NMEA2000 network.

In a previous post we showed how the AISnode could connect to a Raymarine network and in this post we are focusing on Garmin NMEA2000 networks. Garmin adopted the standard NMEA2000 connector system, rather than use their own proprietary connectors and so connection of our AISnode to a Garmin network is even easier, without the need of any special adaptor cables.

Simply find or add a spare “T Piece” connector and the integral NMEA2000 cable of our AISnode will plug straight in, taking its power from the network and sending all received AIS data on to the network.

Garmin’s NMEA2000 AIS implementation is very good and as long as the chart plotter(s) have the latest firmware (free download from the Garmin website) then you will see all of the different types of AIS targets, including the new AIS Man Over Board systems and AIS AtonNs (nav-aids).

For more information on our AISnode, please click here.

Full User Manual now available for new transponders

Transponders 2015

With the recent release of our new AIT1500 and AIT3000 Class B Transponders, we now have three Class B Transponder models in our 2015 product range.

Traditionally, we supply our Class B transponders with a printed Quick Start Guide that provides basic information on installation and operation and for many people this is all the information they need. However, for dealers and customers that want to have more details of using, configuring, installing and fault finding our transponders we have now released a combined Full User Manual for the three units.

To download a copy of the AIT1500/2000/3000 Full User Manual V1.00, please click here.

New AISnode is the perfect NMEA2000 AIS Receiver

AISNode to Raymarine SeaTalkNG Network

Digital Yacht’s new AISnode is the perfect low cost AIS Receiver for the latest generation of small chart plotters that just have an NMEA2000 interface. The diagram above shows how our AISnode would connect to Raymarine’s popular entry level A65 Multi-Function Display (MFD), the first of this new breed of NMEA2000 only chart plotters.

Raymarine’s version of the industry standard NMEA2000 interface, called SeaTalkNG, is fully compatible with NMEA2000, but features their own connectors and additional proprietary PGN messages. To connect our AISnode unit to the Raymarine Network, it is necessary to purchase a SeaTalkNG to DeviceNet (NMEA2000) cable from Raymarine.

Connecting our AISnode to an NMEA2000 network could not be easier as it takes power from the network and puts data on to the network via its NMEA2000 cable (0.75m) which is terminated in a standard NMEA2000 male connector. To connect AISnode to the Raymarine network you will need to purchase the Female version of the Raymarine adaptor cable which is their Part Number A06045 and costs around £20.

AISnode is being officially launched at the Miami Boat Show next week but for more information click here.

You can also download a Dealer pack from HERE

USCG Class A AIS Mandate Now Approved

If you own or operate a commercial vessel in US waters (ports, rivers, lakes, and seas) you are likely to be affected by this new rule. The United States Coast Guard is publishing a new rule which will require most commercial vessels operating in US waters to fit and operate a USCG certified AIS transceiver. On 23rd December 2014, President Obama signed the final rule documentation relevant to the new USCG AIS Rule. We expect it to be formally published in the coming weeks whereupon those vessels affected shall have a limited window of 7 months to install an AIS Class A transceiver to be operating legally.  Currently only vessels over 300GRT on an international voyage are required to have an AIS Class A transponder.  It is likely this ruling will impact on 40,000 vessels.

AIS Basics

An AIS transponder send your boat’s identity, position, course and speed to other vessels equipped with an AIS unit. This data can then be interfaced to a chart plotter display to present an overlay of targets with their heading information.   It greatly aids navigation and helps with collision avoidance.  Signals are transmitted over two dedicated VHF frequencies so typical range from a Class A unit is 20-30NM depending upon antenna height.  All commercial ships over 300GRT are mandated to carry a Class A AIS transponder and the new USCG ruling will also mean other commercial vessels in the US will require a Class A unit.  Class A units have a display to show an overlay of targets and also connect to the vessels electronic chart plotter.  Voyage data can be entered into the Class A display.

Other users including yachtsmen can opt for the cheaper Class B type units like the Digital Yacht AIT1500/AIT2000/AIT3000.  Class B units are fully integrated into the AIS system but have a lower 2W transmit power and only send their data every 30 seconds.  They also require a chart plotter to display target data

What equipment is required?

A USCG approved Class A transponder like Digital Deep Sea’s CLA1000 meets the requirement of the mandate.  Its built tough, is extremely reliable, fully approved and competitively priced as well as supported through a technical dealer network.

The CLA1000 requires two antennas – a GPS antenna (included) and connection to a dedicated VHF antenna.  It may be your vessel already has a spare VHF antenna but if not a good quality (3dBi) VHF antenna should be fitted and ideally a version which is tuned to AIS frequencies (162MHz) which are slightly higher than the normal 156MHz range used for voice traffic.  Digital Deep Sea can help specify the right antenna for your vessel and even have a bundle package available

CLA1000 Bundle HR

The picture above also shows a couple of useful accessories like our HSC100 fast compass sensor which can be connected to the CLA1000 to provide Rate-of-Turn and vessel heading data for the AIS transmissions.  Also show is our Pilot Plug cable allowing connection of a PC or MAC to the CLA1000

What’s in the box?

This video is a little old, but we’ve been in the AIS business for a while which helps us support you better.  Here’s a video showing what’s included with the CLA1000

I know I have to get one but are there any advantages of installing an AIS?

Nobody likes a mandate with deadlines for installation but AIS genuinely improves navigation, safety and will make vessels more efficient for the future.  Unlike radar, AIS positively identifies a target with MMSI, callsign and name allowing communications to be quickly established.  The CLA1000 can also decode ATON (AIS aids to navigation) – these synthetic markers show on an AIS display but may not physically exist allowing dynamic management of the waterways.  AIS Personal SARTs are also available for MOB applications.  Additionally the AIS network can transmit information such as weather to mariners in real time.

iPad, MAC and PC Navigation

The CLA1000 is fitted with a pilot plug connector on the front of the display.  This allows GPS and AIS data to be connected to other devices either wirelessly (to an iPad or tablet using our WLN10HS NMEA to WiFi Server or PilotLink) or via a cable to a PC or MAC.  Digital Yacht has a great range of apps like NavLink US – a full featured charting and navigation program with detailed NOAA charts and a great AIS overlay including vessel scaling

Screen Shot 2014-10-23 at 08.43.55



How do I get more information?

You can get further information on the CLA1000 from HERE

List price on the CLA1000 is $2799 but there’s amazing deals and offers for all commercial operators either through your local dealer or direct from us.  Contact us direct on 978 277 1234 to learn more and get instant savings today.

New AIS Man Over Board Device from Ocean Signal

At this year’s London Boat Show we were interested to see a brand new AIS Man Over board device from UK manufacturer Ocean Signal. The MOB1 is Ocean Signal’s first AIS MOB device, but its specifications, small size and unique integrated DSC function (triggers a DSC Alarm on the boat’s VHF) put it firmly ahead of the McMurdo and Kannad devices.

Ocean Signal MOB1

AIS MOB devices are designed, either to be fitted to self inflating life jackets for automatic operation or carried and manually operated by each member of the crew, should they fall over board. On the assumption that the best vessel to save the MOB is the vessel that he/she fell from, AIS MOB devices transmit a special AIS message that can be picked up by all AIS equipped vessels within 4-5 miles of the MOB.

With a suitable AIS enabled chart plotting device, the position of the MOB is clearly and accurately plotted on the electronic chart, making it very easy to locate and steer back to the “poor unfortunate”. As the MOBs position is constantly being transmitted and received in real time, the fear and uncertainty of trying to predict where the MOB has now drifted to, is completely removed even in rough seas with strong tides.

All Digital Yacht AIS receivers and transponders are compatible with AIS MOB devices, correctly receiving and passing on the special AIS MOB messages to other displays and devices on the boat. For any vessel that does not have an AIS MOB compatible chart plotter or who simply want the security of having an independent AIS MOB alarm system, Digital Yacht’s AIS Life Guard product is ideal.

AIS LifeGuard

AIS LifeGuard

Connected to the NMEA0183 output or the boat’s AIS receiver or transponder, Life Guard will immediately sound its internal 97dB alarm when it detects an AIS MOB signal and also drive an external alarm, relay or klaxon. What is more, LifeGuard can also detect the AIS MOB test message, sounding a short internal beep, ideal for testing the AIS MOB devices before leaving port.


For more information on the Ocean Signal MOB1 device please click here or to find out more about our AIS Life Guard product please click here.