Shape can only overcome so much. The angle of incidence is still an important factor. Have you ever heard of flying under the radar?
Directivity plays a part. All you need at low frequencies is a hardy dipole that can handle 300 watts. A spectrum analyzer, 2 signal generators, triangular wave function generator, pulse generator, and a few mixers. And a parametric amplifier. You do swept AM, FM, pulse and power combined. Fill up the envelope on the spectrum analyzer then connect it to the PA and antenna. It takes 10 minutes to set that up on a bench. I jammed a radio station signal like that when an idiot was listening to particularly shitty stuff near me and very loud. And I likely jammed it for a few miles around.