alliance for continuing medical education A radio signal is usually very weak and should not travel long distances on its own. A method to handle this challenge is to use a strategy called Amplitude Modulation or AM. The technique imposes an additional signal on the already existing carrier wave that transmits the info. The amplitude in the second signal varies (increases or decreases) correspondingly on the amplitude in the first wave. These variations in amplitude or strength are employed through the receiver in order to reproduce audio and visual information (different sounds and images).