CLA1000 Fault Finding Guide

CLA1000 Bundle HR

Despite our popular CLA1000 Class A transponder being predominately fitted to commercial ships by experienced electronic installers, an increasing number are being fitted to pleasure craft and are often installed by the boat’s owner or an installer who has never fitted a Class A transponder before.

Installation is pretty straight forward, but there are a number of steps and procedures to follow:-

  • Mechanical Installation
  • Power Connections
  • GPS antenna installation
  • VHF Antenna installation
  • Interfacing*
  • Configuration via the supplied configAIS program

*Many CLA1000 units are interfaced to our HSC100, USB to NMEA Adaptor cable, Pilot Plug or PilotLink units.

Things do not always go to plan and with this in mind, we have released a Fault Finding Guide to help users, new to Class A transponders, work out what is wrong. To download a copy of our AIS Class A Transponder Fault Finding Guide, click here.


The Non-Idiot’s Guide to AIS

Non Idiots

We had an enquiry today from a US Dealer about why some chart plotters do not display all of the 26 different AIS Messages that are transmitted by Ships, AtoNs, AIS MOB systems and other AIS equipment. This is quite a complex issue as there are three variables at play….

1) The AIS transponder or Receiver

Most AIS receivers and transponders support all AIS messages, however it is true that early Class A and some receiver only units do not support all AIS messages. It is always best for the owner of older AIS units to check that they have the latest firmware in their units and to even contact the manufacturer to see if their unit supports the more recent AIS messages like AtoNs and AIS SARTs (MOB) systems.

The good news for Digital Yacht customers is that every AIS unit we have ever sold supports all of the 26 AIS messages currently defined.

2) The Chart Plotter or Software Application

Even if the AIS transponder or receiver is compatible with all 26 messages, it does not necessarily mean that the chart plotter or software application (running on PC, iPad, etc.) knows how to read and display the AIS messages.

When AIS was first released, many manufacturers and software developers just did a partial AIS implementation, only supporting what they considered to be the most important AIS messages. Also due to delays in the definition of Class B transponder messages, some of the manufacturers only supported the display of Class B targets but not the reading of the Class B static data (boat name, boat type, etc.). Even large manufacturers like Raymarine, Navico and Garmin took a few years to release new firmware for their plotters to improve the number of AIS messages that they supported.

3) NMEA2000 PGNs for AIS

Due to delays in the NMEA committee defining PGNs for AIS, some plotters only support some of the 26 AIS messages when connected via NMEA2000, even if they support all 26 messages via NMEA0183. This Panbo article provides more info on this issue.

To help the dealer better understand some of these finer points of the AIS system, we sent him a copy of our Non-Idiot’s Guide to AIS that we produced for the British Marine Electronics Association.  The 26 AIS messages are detailed on page 12 of this document and the NMEA2000 PGNs are on page 13.

This presentation is a few years old now but is still a useful reference for anyone wanting to learn a bit more about AIS technology. To download a copy click here.

New SmarterTrack Lite V1.04


Today we have released an update to our popular, free SmarterTrack LITE software. Version 1.04 has improved cursor Lat/Lon display in the Status Bar at the bottom of the screen and support for the AIS transponder VDO message which allows SmarterTrack LITE to take the boat’s position from the AIS transponder even if it is not outputting traditional NMEA0183 GPS messages like GGL, GGA or RMC.

A number of people have wanted to use SmarterTrack LITE with the Pilot Plug connection of a Class A AIS Transponder and the new version now supports this allowing you to plot the boat’s position and all of the AIS targets around the boat, via one of our Pilot Plug adaptor cables or wirelessly using our PilotLink product.

Other popular applications for SmarterTrack LITE are; testing a USB or Wireless enabled AIS unit on a Windows PC or for monitoring the local AIS traffic that our AISNet product is sending to Marine Traffic, AIS Live or any of the other internet AIS services. To download a copy of the latest V1.04 please click here.

Getting maximum Wi-Fi range on our PilotLink

PilotLink on Car Mount

Our PilotLink wireless NMEA server for connecting a Class A transponder to an iPad or other wireless device is proving very popular with commercial pilots and ship owners. PilotLink is the only wireless product in our range to feature an internal Wi-Fi antenna but its small ceramic chip antenna is very good and should have a range of 50m or more depending upon environmental conditions.

However, recently one of the Pilots who helped us in the original product testing reported that on some larger vessels, he was only seeing a 20m range. He also reported that if he held the PilotLink vertically and stuck it to the front window of the ship’s bridge that the range would suddenly increase and he could get reception from one side of the bridge to the other.

On checking the antenna data-sheet we confirmed that the antenna gave maximum gain when the Pilot Link was held vertically and also that if the PilotLink was laid flat on a metal surface, which is common when using it on a ship’s bridge, that the Wi-Fi range would be further reduced.


Pilot Link Signal Pattern

The drawing above attempts to illustrate how the Wi-Fi signals emanate from the center of the PilotLink – imagine a large doughnut approximately 100m in diameter with the PilotLink in the middle !

So after reviewing the Pilot’s feedback, backed up by the antenna datasheets, we recommend that anyone needing maximum Wi-Fi range from our PilotLink unit, should mount the PilotLink vertically, as far away from any large metallic objects as possible.

Whilst considering this issue, it occurred to us that a very good solution would be to use one of the many designs of mobile phone holders for cars. Although PilotLink is slightly thicker than your average mobile phone, most of these holders cope with a variety of different sizes and, as you can see from the photo at the start of this article, our PilotLink is held very securely by the spare holder we found in the office.

Mounting of the phone holder is easy, with the suction cup temporarily fixing to the front window of the bridge and, once adjusted for the PilotLink, it is held firmly in place. With these phone holders available from many online resellers and prices starting at just a few pounds, it is even worth considering one for smaller vessels, as a neat way to secure your PilotLink in rough conditions.

ISAF Offshore Special Regs now mandate an AIS Splitter


An important change to AIS installations has now come in to effect for Mono and Multi-Hull Category 0, 1 and 2 offshore racing yachts. The new 2014-2015 International Sailing Federation (ISAF) Offshore Special Regulations (click here to download), that became effective as of 1st January 2014, include an important note that all AIS antennas (VHF not GPS) must now be fitted to the top of the mast.

Due to space and antenna separation issues (see previous post on this subject), it is not possible to have both a VHF and an AIS antenna mounted at the top of the mast, so in order to meet these new regulations, a yacht will need to fit a suitable antenna splitter. It is important that this splitter is suitable for use with an AIS Transponder and we would recommend one of the latest generation of “Zero Loss” splitters that do not attenuate the VHF Radio or AIS reception.

Our SPL2000 splitter is an ideal solution and can even be used with a Class A transponder, which Category 0 Mono and Multi-Hulls are required to fit. Installation is very straight forward (all of the cables are included) and the unit should be mounted close to the VHF radio and transponder.  

Once installed, the SPL2000 will automatically feed the received radio signals to both the VHF radio and the AIS. As soon as either the radio or AIS starts to transmits, the SPL2000 instantly disconnects the other device that is not transmitting. Priority is given to VHF calls and two LED indicators on the front of the unit show when either device is transmitting.

The benefit of using a splitter, and probably the reason for this change to the regulations, is that you get maximum AIS transmit and receive range. This is obviously important when racing offshore, and with the latest “Zero Loss” technology there is now no attenuation of the received signals, which traditionally has been the biggest dis-advantage of using a splitter.

Below is a wiring diagram showing how a splitter is connected to a typical AIS Class B transponder system.

Introduction to Marine AIS White Paper

AIS CPA Alarm Indicators

Although AIS has now been in use around the world for over 10 years, it is surprisingly difficult for anyone interested in AIS to piece together information about this important technology. Wikipedia has a pretty good article on AIS, but we felt it would be useful to take some of the training material we have used over the last few years and publish a White Paper on this interesting subject. If you are thinking about purchasing an AIS or are simply wanting to learn more about what AIS is and why it is an important aid to safe navigation, please click here to download a free copy of our Introduction to AIS White Paper.

Is my AIS Transponder Transmitting ?

Stylised AIS in Action

With lots of AIS Class B Transponders being installed this season, a common question that we are often asked is “How do I tell if my AIS Transponder is transmitting ?”

This is a very valid question and if you have spent a few hours installing the transponder then knowing that it is working OK is very important. Using the proAIS configuration software (supplied with the unit) allows you to see if the GPS position is OK, monitor the AIS reception of other vessels and also ensure that there are no errors or alarms but if you are new to AIS, there is always that nagging doubt as to whether other vessels are seeing you.

The reality is, that as long as the Green Power LED is constantly lit and no other LEDs are illuminated, then the transponder is working correctly and transmitting your position. It usually takes about a minute for the transponder to power up, get a GPS fix and start transmitting. From that point on wards, it is constantly performing a series of internal tests and the Green LED indicates that all of the tests are OK and the unit is operating as normal. It is almost unheard of for the Green LED to be on and the unit not to be transmitting correctly.

The best test of a Class B transponder is to ask someone else in your marina, who has AIS, to check that you are being received on their system. If your vessel is stationary, then a transponder will only transmit every 3 minutes and this increases to every 30 seconds when your speed over the ground (SOG) is greater than 2 knots, so do allow some time for them to detect you. Also when they first receive your transmission, the only data they will see is your position, speed, course and MMSI number, it can take up to 6 minutes for your “Static Data” (boat name, call sign, vessel type, dimensions, etc.) to be received. This is normal and is the way the AIS system regulates the amount of data being transmitted.

The other increasingly common method of testing an AIS transponder is to look on one of the online “live” AIS websites and the most popular of the free services is

However, it is important for you to be aware of the limitations of these online sites and not assume that you will always be picked up by them. Each of the different online services are only as good as their network of AIS receiving stations, that in many cases are operated by enthusiasts/volunteers. In some areas the coverage is great but there are definitely “holes” in coverage.

One of the good features of the Marine Traffic service, is that you can display the locations of the receiving stations and see if they are currently online or offline. From the Marine Traffic home page, zoom in to your location on the map and then on the left hand side of the screen, where there are a series of tick boxes to display different layers of data, click the “More” option which displays some more options. Select the one called “Stations” and then you will see a series of Antenna type icons on the map; green if they are online (receiving data) or red if they are offline.

In the image below (click to enlarge), you can see the popular port of Ijmuiden in The Netherlands. Note the locations of two receiving stations in this area; one at Zwanenburg to the South East and one at Zaanbrug (Wormerveer) to the North East. Both stations are inland and >6 miles away so even though Class A vessels are being received no Class B vessels are shown in Ijmuiden.

Marine Traffic Ijmuiden

A Class B transponder transmits at 2 Watts (about a third of the power of a hand held VHF) so even in perfect line of sight conditions, the best range you can expect is about 8NM. It is important to check if the station is within 5-8NM of your location and also if there are any other Class B vessels displayed near you. If you are more than 5-8NM from the receiving station or there is not good clear line of sight between the station and your location, then the chances are that the station is not picking up your transmission or any other class B transmissions from vessels in your marina.

It should be noted that Commercial vessels and some larger pleasure craft have Class A Transponders that transmit at 12.5 Watts and have a much greater transmit range 20-25NM, so these vessels maybe displayed near your location, even if your Class B transmission is not received.

Finally, it can take an hour or so for a new AIS (MMSI number) to be recognised and stored in the database of these online services so if you are confident that you are in range of an online receiving station, leave your transponder on for a few hours to give the online service time to detect and record you in their database.


Marine Traffic have updated the design of their website since this article was written (click here to see article about this) and the method of turning on the Receiving Stations is slightly different. Now, on the left hand side of the screen, click on the “Layers” icon in the new toolbar and then tick/untick the “Stations” layer.

New MarineTraffic Menu