Theoretical gain of flat microwave reflectors

Flat sheets are sometimes used as microwave reflectors at the top of towers. Calculations are presented showing how these reflectors may produce a system gain rather than a loss, however this gain exists in a qualified sense, as the antenna at the ground level is taken as the gain standard. The reflectors exhibit no gain when the gain standard is an antenna having the same area as the reflector. Reflectors exhibit several characteristics which complicate their use in practice.