State of the art in 2008: the NAIS-300For a long time since its introduction in 2008 the NAIS-300 was the only AIS device on the market that had a NMEA 2000 interface as well as an NMEA 0183. At the time all AIS class B transceivers only had NMEA 0183, a fact easily explained by the fact that at the time all transceivers used the same OEM board manufactured by SRT.
Even before Simrad and Lowrance became part of the same industrial group both companies were early believers and adopters of the NMEA 2000 standard, in some case years earlier than others.
The NAIS-300 was probably the first "joint" product that was going to be used by both brands in the group, and it was also based on the SRT board. In addition to that board it contained a second circuit board that contains the NMEA 2000 interface.
That the NAIS-300 was the first (and only) meant that it did have some rough edges on the NMEA 2000 interface. As the NMEA had not yet agreed on or had time to standardize the PGNs necessary for class B AIS there were only PGNs for class A. Apparently the NMEA assumed that the existing PGNs could be used for class B as well. Thus the NAIS-300 was released with a company specific PGN 130842 for use with class B. It did mean that when used with a non-Navico display you would be able to see a class B device, but you would not be able to see its name, callsign, size of ship etc. The Simrad, Lowrance and B&G plotters understand the 130842 PGN and thus show all information transmitted by class B transponders. There were some additional issues with the NAIS-300 sending out a heading for ships that do not have a compass interfaced to the GPS. All in all the NAIS-300 is better off when combined with a Navico (Simrad/Lowrance/B&G) MFD when interfaced over NMEA 2000. If you don't, or care about the minor rough edges, I recommend you use the NMEA-0183HS output instead.
Fast forward four years
Earlier this year Navico announced the new NAIS-400 and their first AIS splitter, the NSPL-400. The NAIS-400 is again sourced from SRT. The new SRT board offers NMEA 2000 so the Navico engineers didn't have to tack it on, but they do write extra software for it or let SRT do this, as it still supports the Navico specific PGN 130842. Of course it also sends out the now approved standard PGNs 129809 and 129810. The NMEA 2000 interface is almost on par with the NMEA 0183 interface. [Update 2012-01-02:] I say almost because the NMEA 2000 interface does not yet transmit the GPS DOP (precision) data, unlike the slower serial ports. The GPS position data was added in the Nov 31, 2012 software update version 2.5, but DOP is still missing.
An interesting feature of the NAIS-400 is that it has basically three serial NMEA-0183 interfaces, one of which is USB and the other two RS-422. NMEA-0183 data received on the RS-422 ports is sent out over the other ports. This means that you can use the NAIS-400 as a general 2 port multiplexer. You can change the speed of the RS-422 ports in case you want a different speed than the standard 38k4. I had no issues running the RS-422 port A directly with a RS-232 port on my Linux system, but as usual you might have to insert a level converter if you have no success.
I measured the power consumption of a NAIS-400 with all interfaces (NMEA-0183, USB and NMEA-2000) running as 0.17 A at 12.2 V. The splitter power consumption was 0.13 A at 12.2 V.
Together this is still less than the consumption of the NAIS-300 which I measured to be 0.45 A.
So by itself the '400 uses one third of the power and has more features. What's not to like? Well maybe the physical packaging which uses a circular connector and a wire tail that you splice onto your own wiring. The problem with that is that this requires extra connections that are best hidden from sight in a duct. Any my duct near the installation location is rather full.
So installation wise I prefer the older one, but that's really the only bad thing I can say about the new transceiver. Overall, highly recommended.