However, Class B transponders only broadcast at 2 watts, versus Class A's 12 watts. In my Class B experience so far (there was also a 500-mile passage in 2007, outside U.S. waters), I've been pleased that ships usually first see me at six to ten miles, but some users don't feel that's good enough offshore. And B vessels only send out their position message every 30 seconds, at best, while A vessels update theirs at a rate similar to radar scanning-24 times a minute. Thus an A target moves fairly smoothly across a plotting screen, much like a radar blip, while a B target, especially one that's maneuvering, can stutter about. While I haven't yet plotted enough B targets to develop an opinion, there are those that feel the plotting confusion will push some vessels toward filtering out Class B targets, which is a possible option on some plotters (though I'm not sure it should be, or will be forever).