Avoiding interfering with radar unit

You may be able to try it, put something metal in front of the antenna and have someone sit in the car, with the car turned on, it may give some kind of alarm or something if it's blocked. If so then you could just move your pole around and see where it can be located. Seems like the beam width of this antenna must be quite narrow to keep from seeing cars in the adjacent lane so you can probably get pretty close.

 

I recommend looking at the tow hook threaded hole in the front bumper as your front support. It's off to one side so wouldn't interfere with the radar. It should be nice and strong as well, as it's designed to pull the vehicle with.

 

Knowing the radius won't help, you would need to know the radiation pattern. I don't think they would even know what that was and that information is probably not available outside the design team anyway. I didn't realize it only works with the car moving but that does make sense. Which means you need to come up with a way of trying it. I like David Beale's idea of using the tow hook threaded hole, why not rig up a pole that can be secured to one or both and go out and try it? The owner's manual says you will get a warning message and the cruise control indicator will flash if the antenna is blocked (pg 513). I would bet that it will work fine if you can mount the pole(s) to the tow hook holes, they look plenty far enough off center and shouldn't interfere. Maybe a pole bolted to each one with a cross piece on top?