Join Date: May 2007
Location: Santa Cruz
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Just arrived in Puerto Rico after 8 days coming down from Norfolk. The new SR 161 AIS receiver came in very handy offshore. For example, one night it showed a ship coming head on about 8 miles away with a predicted CPA (closest point of approach) of 0.05 miles. It also gave the name of the ship, who responded when I called them on the VHF. They hadn't seen me yet, but agreed to pass port to port. We both altered course to starboard about 10 degrees ( I could see them make their course change on the AIS readout) and passed safely with a mile between us.
Pre AIS, it would have been more stressful for both of us, as I would have been calling them as ' northbound ship at 32-21 north by 68-07 West' (which they tend not to answer), trying to judge their CPA based on radar and range lights, and probably changing my course by 40 degrees trying to get some separation. On their part, a target well inside their rules for the CPA would finally pop up on their radar at about 5 miles out, confused with sea clutter, and my lights might not become visible until about 2-3 miles out, causing some last minute concerns and major course changes on their part.
It was also great to check the AIS as a squall was hitting--when visual and radar contacts were going to be blanked out it was very comforting to know that there were no big ships to worry about for an hour.
The SR161 draws about 0.25 amps at 12 volts, and was hooked to a laptop running the (free) SeaClear II program. The laptop draws less than 0.5 amps in sleep mode and about 2.5 amps while running, so checking the AIS every 20 minutes draws much less power than radar.
The class B AIS transponders will give ships the ability to see us at much greater ranges and a name to call on the VHF to sort out close encounters. There may be some issues in equipping all pleasure boats with AIS in busy harbors, as the screen can get cluttered with targets. However, I think that some changes in the display software would help to distinguish ships from boats. Offshore, I think everyone will be happier and safer with AIS and I plan to install a class B unit soon after they become available.