Why FM is more noise immune than AM?

Answer 1

F.M has low noise in received signal than A.M, the reason is being that Noise signal is amplitude mdulated and will be received by the A.M. receiver and will be rejected by Frequency modulation (F.M) receiver. Because F.M is designed to receive frequency modulated signals.

In the course of communication through electromagnetic waves (em) the message waves are usually not able to traverse long distances due to their large wavelength and hence less energy. So for long distance communication, the message wave is superposed on some other high frequency carrier wave which is known as modulation. That can be done in three ways

1. by changing the amplitude of carrier wave(am)
2. by changing the frequency of carrier wave(FM)
3. by altering the phase of carrier wave(pm)

so as the amplitude and energy of am wave can change due to atmospheric disturbances am is distorted but no disturbances can alter the frequency and hence FM is clearer

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Also, Radio waves are a form of light. When a radio wave is amplitude modulated, it varies the "brightness" of the signal. and a "brighter" source of radio waves, like a lightning bolt or the noise from TVs or Computer equipment is "seen" by the radio easier than the actual radio signal, blocking it out.

FM Radio is like varying the "color" of the radio wave, so if you have a brighter source, you can still see the color of the source (signal), and therefore noise and static.

FM Radio is subject to being reflected in an event called multipath, in which the primary radio signal is reflected by hills and tall buildings, and a secondary signal is received and this causes the ghosting you see on a TV screen or that swishing that you hear on FM in a big city, so FM is still susceptible to noise and static, though not as much as AM.

Answer 2

AM and FM radio waves propagate differently because of their signal strength characteristics. The length of an AM wave allows it to refract against the Earth's ionosphere (a layer of charged particles in the atmosphere) and redirect over the horizon toward a geographical location that could be hundreds of miles away. FM waves in contrast are "line of sight"; the point of transmission must have an unobstructed path toward the receiver. The higher frequency and smaller wavelength of FM signals means that they will go through the ionosphere (and into space) instead of refracting as an AM signal would.

Answer 3

FM radios suppress short term changes in amplitude and are therefore much less prone to noise.