The Grundig Satellit 800 has a special feature called AM Synchronous. This is a useful feature when listening to a medium wave or shortwave station that is suffering from adjacent channel interference and/or fading. The Synchronous Detector in your Satellit can greatly reduce audio distortion that can occur due to signal fading. The Detector also permits selectable tuning in either the upper or lower sideband portion of an Amplitude Modulated signal. Since most medium wave [AM] and shortwave [SW] stations broadcasts employ a double sideband transmission mode, detection of either sideband can result in the full reception of the transmitted information. The selectable sideband tuning and detection not only aids reception permitting tuning into the the stronger (or less distorted) sideband, but also permits rejection of the sideband nearer to the interfering signals.
In the example above the gray signal represents an adjacent signal. The gray-hatched area indicates resulting interference from this adjacent signal. By selecting LSB, the desired signal can be fully recovered from the undistorted lower sideband (LSB).