The Model ATH1G18 is a wide band, high gain, microwave horn antenna that provides a minimum gain of 7dB over isotropic over the frequency range 1GHz to 18GHz. The Model ATH1G18 supplies the constant high intensity fields necessary for RFI/EMI field testing within and beyond the confines of a shielded room. The Model ATH1G18 is also designed to perform emissions measurements. The Model ATH1G18 is compact and light weight for ready mobility, yet is built tough enough for the extra demands of outdoor use and easily mounts on a tripod. The Model ATH1G18 provides the 1-18GHz response required for many often-used test specifications.