Abstract: A small aperture horn antenna comprising an outer conical shell and interiorly of which are formed at least first and second conically flared, dielectric-coated stages of differing flare angles which are coupled to one another via an intermediate cylindrical stage. The dielectric coating is applied to form a uniformly smooth horn interior surface. Mountable to the antenna input aperture are various reflective and homogeneous dielectric refractive focusing lenses and to the output is a low noise waveguide converter. A remotely controlled, axial mount assembly enclosed in a gas-filled, roof mountable radome is also disclosed. Alternatively, the same antenna geometry may be used to transmit a directive electromagnetic wave.