How long has FMCW been used for "speed boxes"? And when "Out of Tune" is mentioned, does that mean completely out of the K band spectrum?

I have an old Uniden 2100W that used to pick up all of these up. Recently I have come across some new ones that it doesn't see. I would have guessed the Uniden was not as picky about specific police radar frequencies as newer detectors. Or could it be the FM throws off the detector because of the unexpected modulation.

Until I read this forum, my first thought was a Ka sign. I know my RD will pick up 34.7, and photar. I am not sure about the other Ka frequencies, but so far in MN and ND, its picked up Ka. Then again I may also have been lucky a few times.