The Model ATH200M1G-1 high-gain horn antenna exhibits increasing gain with increasing frequency (up to 18dB at 1000MHz). With this useful performance characteristic the antenna helps compensate for losses that occur elsewhere in an RF test system - losses which generally increase with frequency. The Model ATH200M1G-1 is well suited for either shielded room or free space testing. Optimum performance is achieved when it is used with our new Model 3000W1000 and 4000W1000 broadband amplifier for RF susceptibility testing. Field strengths generated by the Model ATH200M1G-1 will be identical to those shown by the curves for the Model AT4000 but continuing up to the 10,000 watt level. In shielded rooms, reflections and room losses may reduce the available field. AR suggests a design safety factor of 100% in the selection of power amplifiers.