New plotter
Multifunction displays have developed as rapidly as mobile phones, and many no longer offer a legacy NMEA 0183 input. Garmin’s displays will accept an N0183 signal via the audio port, using a special cable (£35); B&G’S Zeus displays have a similar work-around using an optional video/data cable. The rest, including Raymarine’s Axiom displays, B&G’S Vulcan and Furuno’s Time Zero Touch range do not accept N0183 inputs at all.
In this case, you’ll need to buy a small black box converter that takes your old instrument data in at one end and converts it to N2K. You’ll wire up this ‘gateway’ to the old instrument on one side and plug it in to the N2K network at the other. Don’t be put off by the prospect of a ‘network’ on board. All we’re talking about is a small backbone (simply a single central cable with readymade T-terminals and sections of multicore cable with pre-moulded plugs) into which each of your N2K devices are plugged. It’s a bit like setting up a hose to water plants in your border - you won’t even need a screwdriver to assemble it.
Most marine electronics brands offer their own NMEA gateway. B&G calls its one the AT10 (£110); Raymarine’s is made by Actisense, called the NGW-1-STNG (£165); and Furuno’s is the NMEA2K2. There are also plenty of third-party ones, including Digital Yacht’s flexible ikonvert (£138).
If there’s only one N0183 instrument to connect up, then it’s simple. But when you have several, the task can be harder. Remember that in a NMEA 0183 system, you can’t just wire all the instruments together, because they don’t coordinate their data signals – it is the equivalent of trying to listen to several radio stations at once. ‘When joining together older NMEA 0183 systems to new NMEA 2000 systems, the most important step is to work out the best place to take the NMEA 0183 data from,’ says Paul Sumpner of Digital Yacht.
In the best-case scenario, the instruments will all belong to the same manufacturer’s range and can already speak to each other via a bus system, like Raymarine’s Seatalk, Furuno’s Navnet and B&G’S Network. It means you can take an N0183 output from just one of the instruments and get data from all of the instruments. When I installed a new Raymarine MFD on my Sadler 34, I got wind, depth, speed and temperature all in one fell swoop by using a Seatalk to N0183 converter cable from Digital Yacht (£150). You could also use Raymarine’s own Seatalk to Seatalkng converter, which costs £120 and plugs into your N2K network.
It could equally be an older plotter, GPS unit or an AIS receiver/transponder that is already acting as a multiplexer by gathering signals from several sources. But if you have depth and speed transducers coupled with B&G wind and third-party AIS, then there are only two choices, according to Sumpner. ‘You can either fit a multiplexer to combine the NMEA 0183 data or fit multiple NMEA 0183 to NMEA 2000 converters.’
A multiplexer such as Actisense’s NDC-4 (£225) can accept N0183 data from up to five sources, which it stores and sequences to a single output. Quark Elec produces one that will convert the data to N2K protocol and feed that into the network (QK-A034, £180). However, some warn against the multiplexer solution. ‘They can be tricky to install and configure, plus you end up with one NMEA 2000 device that is putting lots of data on to the NMEA 2000 network,’ explains Sumpner. ‘The current preferred solution is to fit multiple NMEA 0183 to NMEA 2000 converters and have one for the AIS, one for instruments, one for GPS, and so on. This way the NMEA 2000 network structure is more defined and devices can choose which data source to use, rather than be forced to use everything from the multiplexer.’