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What is the disadvantage of FM over AM?

(a) high modulating power is needed

(b) requires high output power

(c) large bandwidth required

(d) high noise is produced

I got this question by my school principal while I was bunking the class.

My question is based upon Generation of AM Waves topic in portion Amplitude Modulation of Analog Communications

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Right option is (c) large bandwidth required

Easy explanation: Advantage of FM over AM is that the amplitude of an FM wave remains constant. In FM, the power of transmitted wave depends on amplitude of unmodulated carrier wave and hence it is constant. FM is less prone to noise compared to AM. However, wide-band FM has a wider bandwidth than AM as it’s BW is given by Carson’s rule which =  2*(β+1)fm, where β = Frequency Modulation Index and fm is frequency of modulating signal. And BW of AM = 2*fm.

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