Computational and experimental methods for evaluating the radiation and coupling characteristics of wide-beam antennas are presented. The application of these methods to a practical antenna is illustrated by a combined theoretical and experimental investigation of a circular waveguide aperture antenna flush mounted in a large metallic ground plane. The design and development of the coaxial antenna, a wide-beam radiator suitable for incorporation into a wide scanning array antenna, is also presented. This antenna is the aperture equivalent of three mutually perpendicular dipoles, and has the capability of transmitting or receiving signals of arbitrary polarization over wide scan angles.