Thales aka Holland Signaal build a radar that can spot sparrows (not Jack) in a tree at 10 km. The problem is not the spotting, its derterming what your spotting. When the Americans came to show their ultra you-can't- see-me-on-radar-plane they cancelled their visit due to the fact that the radar that i mentioned earlier was just outside the gates of the airfield.
So they can see your UAV, and now they can get them down with some force (;-). Its just like space invaders in realtume, if you like to play with the military. I'm more the turn and walk/fly away type.