(4kw Raymarine) is generally a lot of scintillation and targets that appear and disappear until they get pretty close. Except for the big ships, of course. But powerboats and sailboats without reflectors only appear at shorter distances. Seems to be consistent with the RCA data presented in various places. But does bring into question the utility of range alarms, and whether the increase in detection range is really significant to most users for collision avoidance-you still need to be extremely vigilant. Almost talking myself into trading passive AIS for sctive AIS.