Question

Why over modulation is undesirable in Amplitude Modulation(AM)?

Answer 1

Amplitude Modulation:

1. Amplitude Modulation is a straightforward means of sending a signal, such as sound, from one end to the other.
2. A sound is a vibrational source of energy. It moves through the air in the form of waves. This wave is transversal in character.
3. Amplitude and frequency are the two most significant aspects of a wave. The carrier wave's amplitude is modified in accordance with the signal's strength in amplitude modulation.

Over modulation: The signal is considered to be over modulated when the modulation is so significant that the carrier wave clips (distorts in AM) or the frequency varies to such a degree that it goes further than the limit that the receiver can pick it up or overlays other carrier frequencies (in FM).

1. It is nearly always seen as a malfunction. The signal is "off the scale" in layman's words. The modulated carrier emits false emissions, and the restored modulating signal is distorted as a result of over modulation. This indicates that the output waveform's envelope is distorted.
2. Although over modulation is often regarded as acceptable, it should never be used in practice since a distorted waveform envelope would result in a deformed receiving medium output signal.
3. The carrier signal's amplitude is modulated in proportion to the message signal in amplitude modulation. The modulation factor is the ratio of the modulating signal's peak amplitude to the carrier signal's peak amplitude. When this ratio exceeds the value of one it causes over modulation. When the amplitude of the modulating signal exceeds that of the carrier wave, the modulation index exceeds one, resulting in information loss. As a result, in amplitude modulation, over modulation is undesirable.