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Re: Radar reflector proof of concept pic
The Davis reflectors (either metallized foam or aluminum) are comprised of 3 mutually orthogonal, intersecting planes. This creates a "corner cube' reflector. It really shouldn't matter what the heel angle is with these reflectors, as long as the intersecting planes are very close to precisely orthogonal and the projected area remains the same. (Due to the spherical overall shape of these devices the projected area doesn't change with viewing angle.) If the reflective sheets are not in plane and precisely orthogonal you will not get a precise retroreflection--that is, exactly backwards to the interrogating radar.
You can get a sense of how directional the retroreflection is by observing a driveway reflector with a flashlight. (Your typical driveway reflector is comprised of a whole lot of corner cube reflectors.) Start with the flashlight at hip level and bring it up to your temple, where your eye and the flashlight are very close, and you should see a dramatic difference in the reflection. Try this directly in front of the reflector and off to the side and the only difference you'll see should be due to the reduction in the projected area of the reflector (the "cosine law").
Yes, I know there are folks who have tested them and said the "catch rain" position works best, but I don't recall the reason there should be any significant difference due to the angle of presentation.