The QRFH-HA-6-FL is a quad-ridge conical flared horn antenna designed to illuminate microwave reflector antennas over a frequency range from 500 MHz to 18 GHz. The feeds are dual-linear polarized for a given half-angle, subtended by the reflector or sub-reflector facing the feed, specified for each feed. They are constructed from aluminum while the coaxial center line conductor and connectors are gold-plated steel. These horn antennas have a return loss of more than 15 dB over 90% of the band and an aperture efficiency for half-angle of more than 55%. They are available in an enclosure that measures 34 x 40 cm with SMA connectors. A typical feed that has been constructed and tested with a shaped Cassegrain reflector.