Well, I just bought the cobra XRS 9345 (yes I was on a budget. lol) and it seems to be sensitive enough to pick up stupid things like doors etc. But I saw a police officer approaching me on the highway (no obstructions). Looked at my detector... nothing. 100ft... nothing. 10 ft BEEP, Ka band at minimal strength. Is that the detector being stupid or is there a Ka radar function that has low power? IDK. I just bought it today and im going insane. lol.