Originally Posted by Bash
Good point, Paul.
As our resident communications
guru, what do you use on your boat?
I'm junior-guru status at best, and I'm not really a cruiser, but here's my setup (and some comments):
Currently I have a ACR NauticastB Class-B transponder. The dedicated antenna
is mounted on my upper spreader, and the dedicated GPS antenna
is on the stern rail, next to my chartplotter's GPS
and the Iridium
satphone antennas. I have a "stealth switch" that disables the transmitter, although I never use it. The ACR transponder draws about 0.3A @ 12V.
The transponder feeds my NMEA-0183 Shipmodul mux, which combines data from my other NMEA
instrumentation and feeds it all the Furuno Navnet
3D chartplotters, and my ship's computer. The AIS also feeds my Standard Horizon "Matrix" 2000 VHF
currently gets it's GPS input from the chartplotter
, which isn't optimal since I often shut off the chartplotters for power-saving when at sea. The VHF *requires* GPS input on a different port than the AIS, and the GPS has to be at 4800 BPS. It's a stupid design, but the Matrix doesn't recognize the GPS data embedded in the high-speed AIS transponder output. The latest Matrix version may have fixed this oversight. Anyway, when I have the chartplotter
off, the Matrix AIS function is disabled (as is some of the DSC
functionality) because it isn't getting GPS data. I think I can reconfigure my NMEA
mux to make the system work properly, but haven't gotten around to it. Once I get this sorted out, it should be a very low-power AIS solution.
When at sea, I actually use my NavMonPc
program for AIS (and other) monitoring. I run it on a low-power "netbook" or similar, which burns less power than the chartplotters and has (in my humble opinion) a much superior AIS feature-set. I use Expedition for charting and weather
routing on the computer.
I use the chartplotter when I need radar
, or am close to land.
This system is an upgrade from two previous AIS configurations. I started out with a SR-161 single-channel receiver, with a stern-rail-mount antenna. This fed NavMonPc. I actually first tried out the NASA AIS receiver, but was unhappy with that unit. Later, I upgraded to the dual-channel SR-162 receiver. The dual-channel unit was definitely quicker to receive the static ship information, but there was little practical difference in basic dynamic (position, course, speed) acquisition.
In practice, I find AIS to be helpful. It lets me see ships (usually) well beyond my visual horizon, and prepare for any near approach. I do use a hand-bearing compass
to verify our relative courses. I have had ships alter course because they saw my Class-B signal, and have had them hail me by name because they wanted to chat (this is on the high seas, not in the shipping
channels). Of course knowing the ship's name makes it much easier to get their attention when calling in VHF.
The Matrix VHF is a good unit, but I find the user interface to be a little difficult. I have to confess that I haven't yet learned how to use most of the fancy features.
I think for a fairly stand-alone, low power, AIS solution, the Standard Horizon Matrix radio and a Class-B transponder (and possibly a dedicated GPS for the radio) is a good bet. The Vesper transponder also looks very good, and I believe it has a superior user interface.
I also think that you get perhaps 90% of AIS benefit with just a receiver. A transponder does have some advantages, which is one reason I have one.