NMEA 2000

NMEA 2000 is fundamentally different than any other kind of wiring on your boat.

Electrically, it is what is called a BUS.  This means that all devices that communicate over NMEA 2000 cables are using the same wire pair for data, and another wire pair for power.

Any wire has resistance.  Wiring distances matter in any installation, but especially in these networks.

There are four basic elements in these networks.  For clarity, we will start in the middle of the network.  This middle segment, which is like the super highway of the network, is called the backbone.  Backbones can be quite long.  100 feet / 30 meters is not problem.  There is also an integrated shield over top of each pair, and over the entire cable to try to reduce noise.

A properly designed and constructed power cable is the second element of the network.  Power cables can be installed anywhere along the backbone.  And, only the power cable should connect the entire systems shield to ground.  Multiple grounding connections create signal noise .

At either end of the highway, there are signs to tell the electrical signals that the road ends.  These are the terminators.  While small and simple, they are essential to maintaining signal health. The data signals that travel along the backbone are less than two volts.  So, without terminators, these signals degrade significantly.  There must always be two terminators in each boat, at the extreme ends of the backbone.  Terminators are the third element of the network.

The last element in the network are Tees and spur cables, one of each, for each device that is communicating to/from the network.  These connections should not be longer than 10 feet / 3m until they reach the backbone.