Comparison between Frequency Modulation(FM) & Amplitude Modulation(AM)


Frequency Modulation

Amplitude Modulation

1) The amplitude of FM signal is constant and in depth of Modulation.

1) Amplitude of AM signal varies depending on Modulation index.

2) It requires much wider channel (7-15 times) as compared to AM

2) Band width, is very small, which is one of the biggest disadvantages.

3) Transmitters are complex and hence expensive

3) Relatively simple and cheap

4) Area of reception is small since it is limited to line of sight

4) Area of reception is large

5) Noise can be easily minimized. Amplitude variations can be eliminated by using limiter.

5) More susceptible to noise, interference & low signal to noise ratio. Difficult to eliminate effects of noise.

6) Average power in frequency modulated wave is same as contained in un-modulated wave.

6) Average power in modulated wave is greater than carrier power. This added power is provided by modulating source.

7) No restriction is placed on modulated index.

7) Maximum modulation index is 1 otherwise over modulation would result in distortion.

8) Possible to operate several independent transmitters on same frequency.

8) Not possible to operate out interference.

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