Amplitude Modulation (AM) The height of a wave, known as the amplitude, can be
measured in volts (electrical pressure). This is illustrated in Figure 2-19 with a typical sine
wave. In amplitude modulation (AM), the height of the wave is changed in accordance with
the height of another analog signal, called the modulating signal. In the case of an AM radio
station, the modulating signal is the voice of the announcer or the music, which is also an analog
signal. The carrier wave’s frequency and phase remain constant.