You can equip your boat to receive the same AIS signals that are used to create the ship tracking page on BoatingSF.com. To do so, you generally need two pieces of equipment:
If you want your boat to be visible to others with AIS receivers, you need an AIS transponder. Very few non-commercial boats are equipped with transponders today. Transponders come in two types: Class A, which is required on all commercial ships of more than 300 gross tons and on all passenger vessels, and Class B, which is designed for use on boats that are not required to have AIS and thus can use a slightly less-capable transponder. Manufacturers of Class A units, which typically cost several thousand dollars, include Simrad, ACR, JCR, McMurdo, and Furuno. Class B transponders, which are designed for non-commercial vessels, are now available from a variety of manufacturers for less than $1,000.
A much less expensive alternative is a receive-only AIS unit. This allows you to view all AIS transmissions, but not to transmit your own position. One of the least expensive is the SR161 receiver, with an RS-232 interface, which is distributed in the U.S. by Milltech Marine and is currently priced at $189. This low-cost device, manufactured in China by Smart Radio Holdings Ltd., receives on only one channel at a time (there are two channels used for AIS transmissions). It switches automatically from one channel to the other when needed, but this is not quite as robust as a true two-channel unit. For about $400, you can get a more advanced two-channel unit with a USB interface.
You'll also need a standard VHF antenna for the AIS receiver. You can't directly share the antenna used by your VHF transceiver because when you transmit it would blow out your AIS receiver. There are automatic antenna switches available, but you're better off just installing a second antenna.
AIS receivers provide an RS-232, USB, or NMEA output, which presents the AIS information using a standard NMEA protocol. Some recent-model chartplotters are able to decode these signals and display the AIS information on the chart, but older models are not. If you use a notebook PC on board, there's lots of options to view the AIS information. Here's a few of them:
For more information on AIS, see our How AIS Works page.