Sennheiser AD 9000 Directional Active Intelligent Receiving Antenna for Digital 9000 Series Systems (A1-A8: 470 to 638 MHz)The Sennheiser AD 9000 is a directional, active, and intelligent receiving antenna for the Digital 9000 Series EM 9046 receiver. It features the AB 9000 booster, which is directly mounted on the surface of the antenna. The AD 9000 features eight highly selective bandpass filters. Each filter passes frequencies within a 24 MHz frequency window and rejects frequencies outside that range, directly blocking unwanted signals before the first active