The failure of her Class B AIS
transponder to show up on the ships in Sydney
Harbor is disturbing. I know that I will see the ships before they see my lower power Class B transponder, but I have assumed that they will see me when we get a little closer.
A week or so ago I was entering the Chesapeake Bay
early in the morning, when I got a call on Ch 16-"Sailboat at Lat-Long, speed, course, this is US warship 3, 6 miles on your starboard beam." Out of the haze was coming an aircraft carrier, and when I responded to his call he said he was going to follow me toward the bay. I asked him if he saw me on his AIS
, and he said that he had my MMSI, but not my name. This is similar to the findings of the Australian safety
review board, and indicates some shortcomings of the Class B system.
I have had pretty good luck with the Class B transponder in less crowded waters, like watching the Trinidad-Tobago ferry
charge towards me at 37 knots, and make a course change to miss me at about 7-8 miles. I assumed he got the AIS information first, and confirmed it on radar
, but now I'm not so sure. I have picked up other Class B units at about 8-10 miles with a pushpit antenna
, and 12-15 with the masthead antenna
. I have been using the masthead antenna offshore
, to increase the AIS detection range, but I was overwhelmed with 81 targets off Miami
, and switched back to the lower antenna to reduce the system to the closest 50 targets.
I have called a few ships when the AIS predicts a close CPA, and they have all reported seeing me on the AIS. After reading the report, I think that I will be calling more ships to see if they are picking up the Class B transponder and getting my name and vessel type.
I am using the Vesper Watchmate for collision
avoidance, and once you set up its rules on CPA and TCPA for alarms, you have to manually mute each vessel that meets these rules. It is interesting that Jessica had taken a radar
course (but still couldn't see a ship target 1 mile away), but there are no courses on AIS use. I'm sure she is now an expert on both systems.