AM vs. FM: What's the Difference?

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Key Difference

AM stands for Amplitude Modulation, and FM stands for Frequency Modulation. These both techniques are widely used for broadcasting the radio signals that are transmitted in the form of electromagnetic waves. The basic difference between these two technique is that in AM, the amplitude of the wave in the signal is modulated to send the information via radio signals. Whereas, In terms of FM the frequency level of the waves are modulated, and information which is most probably the sound is encoded by modulating the frequency of the signal and amplitude of the wave is constant in this case. The frequency of the wave signal is constant in AM.

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Comparison Chart

 BasisAMFM
Defined asAM is the Amplitude modulation of a radio wave signal to broadcast an audio message to long range.FM is the frequency modulation of a radio wave signal to broadcast a much clear audio message to nearby stations.
Stands for Amplitude ModulationFrequency Modulation
Origin of Technique The technique was introduced in the mid of 1870s. The first successful experiment was carried out in the late 1870s.Edwin Armstrong developed an FM based radio in the 1930s. The first ever frequency based modulation of signals was carried out in America.
Difference in modulation In AM method, the amplitude of the wave is modulated and encoded with sound whereas the frequency is kept constant.In FM method, the amplitude of the wave is kept constant, and frequency is modulated encoding the audio or sound.
Noise issues AM being concerned with amplitude to possess more noise issue as noise directly affect the amplitude of the wave signal.FM, as compared to AM, is quite tolerant of Noise as noise affect the amplitude more but in FM the amplitude is constant, and the sound is encoded via frequency modulation.
Sound quality AM possess poor sound as disturbed by noise.FM has a much better sound quality and noise resistance than AM.
Range AM is lighter and can be sent to long range radio stations.FM range is quite less as compared to AM.
Cost AM is cheaper as compared to FM.FM is expensive as compared to AM.
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What is AM?

AM stands for amplitude modulation. It is one of the first methods of transmitting signals and audio information via radio signals. The messages or information is encoded with the amplitude of the wave and then transmitted or broadcasted as electromagnetic wave signals to long range radio stations which receive and decode the information by amplifying the amplitude of the wave.  The technique was first introduced in the mid of 1870s, whereas in the late 1870s the first successful experiment was carried out. The technology or this particular method was later on replaced by FM but was used still due to its ability of broadcasting to longer range. In this method, the frequency of the wave is kept constant whereas the amplitude of the wave is modulated and the audio message is encoded with it. AM method possesses very poor sound quality as it is resisted by noise a lot. The noise and other distortions directly affect the amplitude of the wave due to which the sound quality is poor as the audio information is encoded with modulated amplitude.

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What is FM?

FM stands for Frequency Modulation. It is the technique that replaced the AM amplitude modulation due to much better sound quality and is more tolerant of noise and distortion. Edwin Armstrong built the very first FM based radio that was capable of transmitting radio wave signals by modulating the frequency of wave instead of amplitude. The very first FM based successful transmission took place in the United States of America. FM method differs in approach from the AM method. In FM, the amplitude of the wave unlike in AM is kept constant, whereas the frequency of the wave is modulated and the sound as information or message is encoded with frequency. These electromagnetic waves were then transmitted to various nearby radio stations which decode the message by modulating the frequency of the waves. The sound quality was quite better than AM as it was more noise resistant. Noise affects more amplitude than the frequency of a wave. The only issue which this technique is that unlike AM, the messages cannot be broadcasted to the longer range. They are only captured by nearby radio stations only.

AM vs. FM

  1. AM stands for Amplitude Modulation.
  2. FM stands for Frequency Modulation.
  3. The amplitude of a wave is modulated in AM.
  4. The frequency of a wave is modulated in FM.
  5. FM possess better sound quality than AM.
  6. AM possess higher transmission range than FM.
  7. AM technique is cheaper than FM.
  8. FM is the modern version of AM.

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