This article describes a circularly polarized feed horn designed to feed shallow, prime-focus or offset-fed parabolic reflectors. Both circular polarization senses are available at two individual coaxial ports. The design provides good circularity, a very clean radiation pattern with excellent sidelobe suppression, outstanding isolation between ports, and needs no adjustments. An L-band example is presented, including both simulation and experimental results. The complete set of dimensions, not previously found in the literature for septum polarizers in circular waveguide, is provided for the practical engineer who desires to duplicate or scale this feed horn to other frequencies.