Its a real nuisance that the Raymarine C120 has only one NMEA port and that once you have set this to receive AIS data at 38,400 bd it cannot then talk/listen to NMEA 0183 data at 4,800 bd.
Having struggled with various configurations I eventually discovered the excellent Brookhouse multiplexer from New Zealand and got one shipped over to England. This is a great bit of kit and after a few false starts I have managed to connect it up very successfully to the Raymarine E85001 interface box – that I had already bought – but now realise is redundant.
The Brookhouse can take in Seatalk and NMEA0183 (old) and NMEA2000 (new and used by AIS) as well as output NMEA0183 or NMEA2000 (eg to the Raymarine C120) and also has a dedicated USB bus to connect to a laptop.
This is how to connect the NASA AIS Engine to the Raymarine C120
For diagrams from the supplier in New Zealand click here