Ya did really good...
Just one point... to effectively refract i.e., focus radio waves the
antenna can be as small as one half wavelength in dimension...
If I had a chalk board on here where I could scribble and wave my hands it
would become clear - taint clear unless I talk with my hands - It's the
time/phase delay due to C that allows a half wavelength structure to
effectively refract,
i.e. the arrows all add up to the shortest path - see R. Feinman, et. al.

Larger is better, however... Look at the dish at Arecibo for example..
http://www.rainforestsafari.com/observe.html
It is an efficient focuser of very weak, short wave length, radio waves
because it is many wavelengths across, gathering numerous wave fronts in
phase, and focusing them on the sampling probe...

Similarily, a camera lens that works efficiently at lower light levels will
be larger in diameter for a given focal length than one that doesn't work as
efficiently... i.e., an f:2.8 lens versus an f:1.4 lens..

denny
"Katherine" wrote
To noticably refract radio waves, I think you'd need something with a
thickness at least on the order of the wavelength of the waves. VHF
radio has wavelengths on the order of several meters.

Hope i did all that math right,

--Kath