With the switch to the RS35 radio, I got rid of the only NMEA0183 device in my boat and could start to install a NMEA2000 network.
WARNING: NERD SPEAK FOLLOWS
NMEA0183 is a serial based communication standard that all boat equipment used to use to talk to each other. This has been replaced by NMEA2000 in all newer equipment, which is a lot like the common ethernet standard that’s used in modern LANs.
NMEA2000 has a lot of advantages compared to the older standard:
– Can run off a backbone style system – no need to daisy chain point-to-point as in the NMEA0183 system
– Though NMEA0183 is a standard – there is no certification process! Which means that different manufacturers implemented it in different ways. This required a lot of fiddling, and often sometimes stuff just wouldn’t talk to another manufacturers stuff.
– NMEA0183 doesn’t have much ‘bandwidth’ – being able to send only 12 messages a second.
– NMEA2000 is pretty much ‘plug and play’ since it includes a physical layer – NMEA0183 doesn’t.
So with that technobabble out of the way, it was time to start my N2k network.
First, a bought a starter kit, which included two terminators, 2 t connectors and a power cable. Old networking gurus will remember the old ‘ring network’ LAN standard, and this reminded me a lot of that!
NMEA2000 is set up with a ‘backbone’ cable, with instruments connecting off that with ‘t pieces’ and a terminator at each end of the backbone cable. In addition, at some point on the backbone cable, there needs to be a power cable connected to a 12v source.
So my initial network looks like this:
Now physically, it doesn’t actually look like that – the T pieces are all joined together, meaning I only needed two drop cables and 1 power cable.
I hooked up the power cable to a spare breaker, called ‘electronics’.
Once that was all done I tested – and not only did my radio pick up the GPS, but then my plotter also picked up AIS targets!
For those who don’t know what it is, AIS is a system that broadcasts a vessels position, intentions and callsign/name over a VHF radio, using a vessels MMSI number that uniquely identifies the vessel. These show up on my chartplotter as a triangle (see above). One of my upgrades is going to be to fit an AIS transponder so that I will broadcast my own signal.