Back in 2008 I installed a very inexpensive Automatic Identification System (AIS) receiver for the SO36i I then owned and I thought others may be interested in the process.
It is now a legal requirement for all ships over 300 tons to have on board an AIS transmitter that provides quite detailed information to any other vessel that has the required receiving equipment. I purchased a Milltech SR161 AIS receiver from the Milltech website for $189 and rate it as the best value for money I have ever spent.
The output of the SR161 goes directly to the NMEA port of the Raymarine E80 chartplotter. The output of the AIS receiver is set to 38,400 baud as standard and the chartplotter must be set to accept this data rate. This is done on the E80 by accessing the “system integration” menu.
I used to send GPS data to the VHF from the output of the chartplotter NMEA port for co-ordinates for the DSC system. When the baud rate was set to 38,400 this feature no longer worked because the standard NMEA rate is 4800 baud and that is what the VHF radio expected. I now take the GPS data from the NMEA output of the Raymarine SG1 autopilot computer and it works like a charm.
At first I tried to provide the AIS data to the NMEA input of the autopilot computer as I thought it would translate the information to the Seatalk network and the chartplotter would get the AIS information from the Seatalk network. Although I read as much as I could (read the manuals from cover to cover) no information on the translation of AIS data was available until I contacted the Raymarine technical support service. I was informed the chartplotter could only get the AIS data from the NMEA port. The manuals were not very detailed but the technical support service was extremely fast and very helpful. Congratulations to Raymarine for that service.
Also available from Milltech is a system for splitting into the existing VHF antenna on the yacht. I chose not to use that system as I simply used the rubber duckie antenna supplied by Milltech with the receiver. I figure I am only worried about ships that are close enough to run our yacht down so optimum long range reception is not a priority. The rubber duckie antenna works just fine and I can “see” ships 10 Nm from us.
The installation of the AIS receiver in the aft locker on our 2 cabin SO36i is shown below. Simply add power, put on the antenna and connect the serial port to the NMEA input on your chartplotter.
Below can be seen the chartplotter display of the information that is available from the receiver. The chartplotter indicates the heading and speed of the ship, its closest possible distance from our yacht if we both maintain current course and speed and the time that will occur. If the ship is regarded as a dangerous target as defined by user preset parameters on the chartplotter, alarms sound to alert the helmsman. The red circle indicates the 2 Nm exclusion zone can be seen around our yacht on the chartplotter.
This system can work for any modern chartplotter allowing for AIS data. I think the value for money is just outstanding and is an essential safety item for any offshore yacht.