AIS, this and that #1
Whereas so many of you are interested in AIS, and so many news bits keep coming in, I’m starting a “this and that” series…
* Nobeltec has put up the best looking AIS 100 manual to date. Above is a wiring illustration, including how to pass GPS data through the AIS 100, though Nobeltec does not recommend doing so. (For them it’s largely an issue of technical support, but I also understand that the AIS 100 only passes through the GPRMC data string, which may mean that you won’t be able to see, say, how many satellites a GPS is receiving. Anyone know for sure? {The answer is yes, confirmed by GPSNavX in comments})
* Meanwhile, NASA has apparently changed the firmware in the AIS 100 so that it now automatically switches channels every 36 seconds, which seems like a good idea. Supposedly it is possible to update older units, but I don’t know how, or where you can get the update (yet).
* Navicon, a Danish company doing a lot of AIS software development, has introduced a Java-based charting program called AIS Navigator.
* True Heading, a Swedish AIS company, has developed a splitter for sharing a single antenna with an AIS receiver and a regular VHF radio. Look in Products/Accessories. They also have a new product called Blue-Pilot which uses Bluetooth to make a Class A transponder’s “pilot port” wireless. Better yet, it is supposedly able to find and correct problems in the plug installation (which are said to be common). Look in Products/AIS, where you’ll also see the Smart Radio 161 single channel receiver recommended for shore use only.
From the Nasa Marine Engine Specification..
"Data format (GPS RMC sentences from Engine to PC)
NMEA RMC sentences received on a separate input channel at 4,800 Baud (on pin 9 of the 9-pin DB-9 socket) will be copied through on the 38,400 Baud output channel whenever they are available. RMC sentences are re-transmitted only if the CRC check on the incoming data is passed, and are sent whenever they are available."
So this means if you connect your GPS into the Nasa AIS marine receiver you will only get the $GPRMC message passed through and only if it has a check-sum (most do). All other messages will be lost, such as $GPWPL or $GPGSV which are the active waypoint or satellite information. One should avoid running the GPS through the Nasa receiver if possible. Ideally a seperate port should be used for GPS (4,800) and AIS (38,400).