For the best AM/FM stereo reception nothing works better than a vertically mounted antenna mast. Realizing that application is impractical on some trucks their improved 12 volt amplified antenna is the next best thing. Mounts on the inside top of windshield or rear window for best performance. Its completely non-directional and requires no grounding or drilling. Note: Radio signals cannot penetrate metal. Do not attempt to hide this unit under the dash.