Originally Posted by liberty16
I see that the Si-Tex AIS has an alarm function to alert you if something enters "a preset range ring", but does the NASA AIS also have that?
Nasa actually makes the "AIS Radar" unit that Si-Tex sells, and Nasa also sells this unit under their own name as well. This is a stand-alone AIS receiver (single-channel, frequency-switching), and processor/display, all in a nice small package. You need to connect a NMEA GPS
input to this unit. I've read that it works reasonably well, but is a bit rough around the edges. It does not process Class-B AIS, which at the moment isn't a big issue (in the USA, anyway).
Nasa also makes the "AIS Engine", which is a receiver only, and is intended to be connected to an AIS-ready chartplotter
or computer. The SR161 is a similar unit (single-channel, frequency-switching), and the SR162 is a dual-channel unit. I think the SR161/162 are better, and I have all three. The Nasa AIS Engine
does not handle Class-B, but if you want to open up the unit and do some digging around there is a third-party aftermarket replacement chip available that is supposed to provide Class-B support.