Complex sentence: Many things can act as a demodulator, if they pass the radio waves on nonlinearly: for example, near a powerful radio station, it has been known for the metal sides of a van to demodulate the radio signal as sound.
Split into simpler sentences: Many things can act as a demodulator, if they pass the radio waves on nonlinearly. For example, near a powerful radio station, it has been known for the metal sides of a van to demodulate the radio signal as sound.