Just ordered one. Will let you know how it goes.
I have been studying the interaction between simple one-channel AIS receivers and most Class B transponders, and the results are a bit concerning, if my data and observations are true.
I have been using an SDR for spectrum analysis, and a dAISY programmed for single-channel-only mode to look at some real life data.
1. I find that most (all?) single
channel receivers only switch channels when they detect an error on receive, usually due to transient noise
2. I also find that many Class B transponders transmit on only one of the authorized TX channels, most of the time. They are supposed to alternate channels for "periodic repeated" messages, but they don't all seem to do this.
Result: If I am listening on Channel 1, and your transponder is stuck on Channel 2 for a long time, I may never see you. Or it may take a very long time (multiple minutes). This problem is exacerbated by the long reporting period and subordinate network access methods of Class B transponders.
So, in short, I'm beginning to conclude that the utility of Class B for inshore work
to be compromised and sometimes dangerously misleading for collision
avoidance. This does not mean that the utility for offshore
avoidance is null. It just means that one should not rely exclusively on AIS-B for close-in navigation
But we knew that already....