I'm a current DoD contractor employee at Griffiss, and it's a real trip to see just how much cool stuff is/was being done at the base when it was still active. There is still cool research being done but nothing at this scope for a while now. It makes me kind of sad to see all of this activity being sent away from NY to Cali, Nevada, New Mexico, Texas, etc. Not a whole lot of large-scale testing/development going on up here nowadays. Getting stories from the old timers is always fun, though.
There (was) also ATLAS-I or "Trestle" ( https://en.wikipedia.org/wiki/ATLAS-I ) at Kirtland Air Force Base near Albuquerque, New Mexico to park airplanes onto for EMP testing. The largest non-nuclear electromagnetic pulse generator in the world.
I used to work at AFRL as an intern and a contractor, there were pictures of these platforms in a bunch of the buildings. I also played in a golf league in Newport NY. You could see the platform from a few of the holes.
> Instead of flying the aircraft over test antennae, the airframes (usually minus their tails) are suspended upside-down, under or near the instrumentation.
Why not make a hole in the ground and put the antennae under the airplane that way?
I was intending to put the test equipment in the hole.
Since "flying over test antennae" was an option, it shouldn't be a problem that there's solid ground (the bottom of the hole) underneath the test equipment.
I think the real answer is that they need more angles than keeping the aircraft flat and level and putting the antennae below it would provide. The aircraft have to be suspended anyway, so they can be rotated and have different profiles measured.