What is a disadvantage of amplitude modulation?

• A. It is cheap and easy to implement
• B. It is prone to noise
• C. It is highly resistant to noise
• D. It has excellent spectrum efficiency

Answer: (C)

Amplitude modulation carries information in the signal’s amplitude, so any noise or interference that alters that amplitude becomes part of the demodulated output. This means the envelope—the carrier’s amplitude that encodes the data—can be distorted by noise, degrading the information especially when the received signal is weak. In practice, this yields poorer signal-to-noise performance for AM compared with modulation schemes that encode information in frequency or phase, which are less affected by additive amplitude noise. While AM is cheap and easy to implement, and widely used, its susceptibility to noise and its relatively inefficient use of bandwidth (due to the carrier and two sidebands) are the main disadvantages.