  A finite-difference time-domain (FDTD) numerical analysis is used to
demonstrate that a toroidal solenoid, coaxial with an electric dipole, is a
remarkable non-radiating configuration. It can be used to measure the
dielectric permittivity of any ambient matter. It becomes a directional
radiator at an interface between two dielectric media, depositing energy in the
material with the highest polarizability.
