This week we have been helping one of our dealers; Marine Electronic Installations (MEI) in Portsmouth, to find a solution to an interesting NMEA2000 problem with the latest range of Raymarine a, c and e Series Multi-Function Displays.
Most of these MFDs feature an internal GPS, a SeaTalkNG (NMEA2000) interface and an NMEA0183 interface. Under normal circumstances, if you connect one of our AIT2000 or AIT3000 transponders to a Raymarine MFD via SeaTalkNG (NMEA2000) the MFD will use its own internal GPS as the position source and receive the AIS target information from the transponder.
What MEI discovered, was that when a Raymarine SeaTalk 1 to SeaTalkNG converter (E22158) is fitted to the network, that the MFD stops using its internal GPS and tries to use a GPS source on the SeaTalkNG network. As our transponders are outputting the Rapid Update GPS PGNs on the NMEA2000 network, the Raymarine sees this as a GPS source and tries to use it but then reports an “AIS Position lost” alarm because the GNSS PGN that provides GPS status information is not being received.
This seems to be a unique problem to Raymarine and not one, so far, reported on other systems. For instance the latest Garmin plotters always default to using their own GPS and ignore the GPS data from the AIS transponder. Also it only occurs when this SeaTalk 1 to SeaTalkNG converter is in the system, although this is quite a popular accessory and used when boats have older ST50/ST50+/ST60/ST60+ instruments or autopilots with a SeatTalk 1 interface.
We have found two ways to fix this problem;
1) Connect the AIS Transponder to the Raymarine MFD via NMEA0183, which is fine for units that have an NMEA0183 input (all units except a6X and a7X )
2) Send a special configuration command to the AIT2000/AIT3000 transponder via the proAIS2 software that turns off the NMEA2000 GPS data
For more information on this configuration command please email firstname.lastname@example.org