The Model ATH33G50 is a wide band, high gain, high power microwave horn antenna. With a minimum gain of 20dB over isotropic, the Model ATH33G50 supplies the high intensity fields necessary for RFI/EMI field testing within and beyond the confines of a shielded room. The Model ATH33G50 is extremely compact and light weight for ready mobility, yet is built tough enough for the extra demands of outdoor use and easily mounts on a rigid waveguide by the waveguide flange. Part of a family of microwave frequency antennas, the Model ATH33G50 provides the 33-50GHz response required for many often used test specifications. The Model ATH33G50 standard gain pyramidal horn antenna is electroformed to give precise dimensions and reproducible electrical characteristics. The Model ATH33G50 is used to measure gain for other antennas by comparing the signal level of a test antenna to the signal level of a test antenna to the standard gain horn and adding the difference to the calibrated gain of the standard gain horn at the test frequency. The Model ATH33G50 is also used as a reference source in dual-channel antenna test receivers and can be used as a pickup horn for radiation monitoring.