Installing the NMEA2000 network backbone

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 This has been replaced by NMEA2000 in all newer equipment, which is a lot like the common ethernet standard that’s used in modern LANs.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:

NMEA2000

 

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!

AIS1

AIS2

 

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.

 

Matt

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