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Interested in using one of our AIS Receivers or Transponders with a Chart Plotter? This Tech Note provides an overview of how to do it.

By Doug Miller, Milltech Marine Inc.

AIS Receivers can be used with chart plotters that support connections from AIS receivers. If you have bought a Comar AIS-2-NMEA or AIS-MULTI AIS Receiver product or an ACR Nauticast-B or Comar CSB 200 Class B AIS Transponder, you can ignore most of this page and simply follow the directions that come the products and connect the NMEA output wires from the AIS system to the NMEA input wires in the chart plotter. In general, if you are planning on using an AIS receiver with a chart plotter that uses true NMEA 0183 input and output, you should buy an AIS receiver that has true NMEA 0183 output capability. This feature is included in the Comar AIS-2-NMEA and Comar AIS-MULTI AIS receiver products. In addition the ACR and Comar Class B AIS transponders support true NMEA output signals and can be used with chart plotters that support input from AIS systems. If you are connecting the ACR Nauticast-B transponder to a NMEA chart plotter, then connect the Nauticast-B ORANGE RS422 TX A wire to the NMEA positive input wire on the chart plotter and the BLACK RS422 TX B wire to the NMEA negative input wire on the chart plotter.
Click here for ACR's Compatibility Statement for the Nauticast-B product.

NOTE: The Smart Radio AIS Receivers use an RS232 serial port to exchange data with devices. This works well for devices such as computers, however the Smart Radio products often do not work well or are can be damaged when used with a chart plotter. Therefore do not use Smart Radio products with chart plotter systems. In addition, some chart plotters use NMEA RS422 electrical signaling which is not compatible with the RS232 signals that the Smart Radio units use.  NMEA RS422 chart plotters include all Raymarine chart plotters and the Garmin 4000 and 5000 series chart plotters. If you have one of these systems, then please consider using the Comar AIS-2-NMEA or AIS-MULTI AIS Receiver. Again, do not use Smart Radio AIS receivers with chart plotters.

AIS support is a fairly new feature with chart plotters so this will only work if you have a chart plotter that is typically less than 2-3 years old. However, most of the popular current chart plotter models now support AIS. This includes:

  • Raymarine C Series. E and G Series
  • Garmin 3000, 4000 and 5000 models
  • Standard Horizon CP chart plotters

As well, many other models from other vendors also work with AIS. Check with your chart plotter vendor to ensure that AIS is supported.

What is required to connect an AIS Receiver to my chart plotter?

On the AIS Receiver end, you need:

  • A Comar AIS-2-NMEA or Comar AIS-MULTI AIS Receiver or an AIS Transponder such as the ACR Nauticast-B or Comar CSB 200.
  • A dedicated connection to a new or existing VHF antenna with our "SO239 to BNC Connector" or use our AIS antenna which includes a BNC connector or install one of our VHF Antenna Splitters or the Comar AIS-MULTI to use your existing VHF antenna,
  • A connection to 12 volt DC power for the AIS Receiver and the optional VHF Antenna Splitter,
  • If you are using an AIS Transponder or a Comar AIS-2-NMEA or AIS-MULTI Receiver, the NMEA cables are included and will be used to connect to the chart plotter.

On the chart plotter end, you will need:

  • A cable supplied by the chart plotter manufacturer for connecting optional NMEA or RS232 devices,
  • Your chart plotter installation manual (in order to determine which wires to connect to),
  • A method for connecting the output wires from the AIS Receiver to the input wires on the chart plotter (e.g. a patch panel or terminal block).

If you are also connecting to a computer, you will need:

  • For AIS receiving, use a Comar AIS-MULTI which includes both a NMEA output for connection to a chart plotter and a USB output for connection to a computer.
  • For AIS transponders such as the ACR Nauticast-B and the Comar CSB 200, there are connections for both NMEA output to a chart plotter and RS232 serial output for a computer. If your computer does not have a serial port, then you will need a Keyspan USB Serial Adapter.
How do I connect the AIS Receiver or transponder to the chart plotter

Before attempting to connect your AIS device to a chart plotter, please ensure that power is turned off to all devices. We mean it! Any attempt to wire your AIS device to another device with the power on to either device will result in damage to your AIS device and will void your warranty.

Only two wires should be connected between the AIS device and the chart plotter. Normally chart plotters have one or more NMEA or RS232 input / output ports for connecting peripherals such as AIS receivers. Chart plotters use a system for input ports based on one of the following two standards:

  • Some chart plotters use a single signal wire for each inbound port and share a common ground for all input and output ports. For the Comar and ACR products, the NMEA +ve goes to an available chart plotter input signal wire and the NMEA -ve is connected to the common ground wire. For example, Garmin 3000 models and the Standard Horizon CP180 use this system.
  • The other method used by some chart plotters uses a pair of wires for each NMEA input port with one wire being a positive signal wire and other wire being a negative signal wire. The negative signal is isolated from the ground system on the boat. These systems are typically using NMEA/RS422 electrical signal voltages and not RS232 signal voltages, therefore do not use a Smart Radio AIS Receiver with these types of chart plotters. For the Comar and ACR products, the NMEA +ve goes to an available chart plotter input positive signal wire and the NMEA -ve is connected to the input negative signal wire for the same port. If you are connecting the ACR Nauticast-B transponder to a NMEA chart plotter, then connect the Nauticast-B ORANGE RS422 TX A wire to the NMEA positive input wire on the chart plotter and the BLACK RS422 TX B wire to the NMEA negative input wire on the chart plotter. For example, Garmin 4000 and 5000 chart plotters and Raymarine C, E and G Series models use this system. For best results use an AIS device that supports true NMEA RS422 signals (e.g. our transponders or the Comar AIS-2-NMEA or AIS-MULTI AIS Receivers) if you are planning on using AIS on a NMEA-only chart plotter. Do not use Smart Radio AIS Receivers with these types of chart plotters.

Consult the installation documentation for your chart plotter and AIS device before attempting to connect your AIS device to a chart plotter. Incorrect installation can result in damage to both your AIS device and the chart plotter.

NOTE: The input wire for the AIS Receiver that is typically connected to pin 3 must not be connected to any wire on the chart plotter. As well, the output wires from the NMEA ports on the chart plotter must not be connected to the AIS Receiver. Once again, before attempting to connect your AIS receiver to a chart plotter, please ensure that power is turned off to all devices. Any attempt to wire your AIS receiver to another device with the power on to either device will result in damage to your AIS receiver and will void your warranty.

Once the wires have been connected correctly and power has been turned on to both devices, you will need to set the baud rate on the chart plotter to the correct speed. By default, most chart plotters use 4800 baud for each port however the baud rate for the AIS Receiver is set to 38400 baud by default. To resolve this, you need to ensure that the chart plotter baud rate for the port you are using is set to 38400 baud or "high speed". See your chart plotter documentation for instructions on how to do this. As an alternative, you can change the baud rate on the AIS Receiver to 4800 baud. See our product documentation for details on how to do this. Finally, you may need to turn on or configure the display of AIS targets using your chart plotter set up menus. Again, see your chart plotter documentation for instructions on how to do this.

Garmin 4000 and 5000 model notes

The Garmin 4000 and 5000 series models use a paired signal wire system for the input ports for connecting NMEA devices. Smart Radio AIS Receivers are not supported for use with Garmin 4000 and 5000 chart plotters. This problem is due to the signal voltages used the Garmin device. The Comar AIS-2-NMEA, AIS-MULTI and the AIS transponders products do not have this issue and should work without modification with all Garmin models.

Raymarine C and E Series notes

The Raymarine C and E Series products also use a paired wire system for connecting an input NMEA device, so the above instructions for connecting to systems using paired signal wires will work fine. The following diagram from Raymarine's installation documentation shows the pin-outs for the NMEA Input Cable.

Raymarine NMEA connections

We do not support using any Smart Radio AIS Receivers with Raymarine chart plotters since these chart plotters use true NMEA RS422 signaling. For best results use one of the Comar AIS products (AIS-2-NMEA or AIS-MULTI) or one of our AIS transponders and simply connect the two NMEA output wires from the AIS device to the white NMEA Input (+ve) wire and the green NMEA Input (-ve) common wire on the Raymarine NMEA 0183 cable. If you are connecting the ACR Nauticast-B transponder to a Raymarine C or E series chart plotter, then connect the ORANGE RS422 TX A wire on the Nauticast-B to the WHITE NMEA input positive wire on the chart plotter and the BLACK RS422 TX B wire to the GREEN NMEA input negative common wire on the chart plotter. Note: the Raymarine NMEA 0183 Cable is required to connect an AIS receiver to the Raymarine chart plotters. This cable plugs into the back of the chart plotter and is supplied by Raymarine. The cable has bare leads on the end for mating with NMEA devices such as AIS receivers.

Summary

These are the basic steps. Once you have your AIS device connected to your chart plotter, you should see icons for both your own position and for AIS transponder-equipped vessels that are near you. However, some customers have noted that even if the systems are wired correctly, the chart plotter will not show the AIS system as being active. This is due to the way some chart plotters recognize an AIS receiver. In order for it to "see" the receiver, valid AIS data must be coming into the input port on the chart plotter at the correct baud rate. So if the baud rate is not set to the same value for both devices or if there are no AIS targets nearby, then the chart plotter may indicate that AIS is not active. To resolve this, ensure that the baud rate is set correctly and you are in an area that has AIS targets. Most chart plotters include the ability to "zoom" into the target to view the full information about the vessel such as the vessel name, call sign, destination etc.

For more information on this subject, see our FAQ page, the online AIS Troubleshooter and the product documentation that comes with the AIS Receiver and your chart plotter. If you have additional questions, send email to: info@milltechmarine.com.

 
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