Difference Between AM and FM

Radio broadcasting started on this planet by 1905 on an experimental basis. Around 1920, it became commercial broadcast too.

In the early days of the radio broadcast, the stations used long-wave, medium-wave and short-wave bands for broadcasting. Over time, Very High Frequency and Ultra-high Frequency broadcast modes came into existence.

Amplitude Modulation (AM) and Frequency Modulation (FM) are the two different modes of radio broadcast. Both modes help transmit information in the form of Electromagnetic Waves.

AM vs FM

The main difference between AM and FM is, AM modulates the amplitude of the signal keeping the frequency constant and FM modulates the frequency of the signal keeping the amplitude constant.

AM vs FM

Amplitude Modulation came into existence earlier than the Frequency Modulation. The discovery of FM radio signals is a type of upgrade in the signal clarity when compared to AM radio signals.


Comparison Table Between AM and FM (in Tabular Form)

Parameter of ComparisonAmplitude Modulation (AM)Frequency Modulation (FM)
ModulationIn AM, the carrier wave is modulated in the amplitude keeping phase and frequency to be constant.In FM, the carrier wave is modulated in the frequency, keeping phase and amplitude be constant.
Cost FactorAM transmission and reception are of low cost.FM transmission and reception is relatively costlier than the AM systems
Quality of SoundThe Sound Quality is rather poor in the case of AMThe interference in the case of FM is less, thus making the sound quality the best.
Complexity in FunctionalityThe Transmission and reception functionality is very simpleThe Transmission and reception functionality is highly complex
Distance of BroadcastAM signals can be transmitted over a long distance.FM signals cannot be transmitted over long distances. Many FM radio stations are required for this purpose.


What is AM (Amplitude Modulation)?

Amplitude modulation is a process by which the radio wave signal is transmitted by modulating the amplitude. AM is used in the form of electronic communication.

AM is the oldest and earliest method of transmitting information as radio signals. While the carrier does not vary in amplitude, but the modulating data transforms it for the transmission.

Amplitude Modulation is very simple to implement compared to any other forms of radio transmission and reception. AM requires limited bandwidth too.

AM is not expensive, and this makes it useful for long-distance transmissions. The transmitter and receiver components are also not complex makes it economical for usage.

AM consumes more power for transmission as well as the reception. AM signals require very high bandwidth, at times equivalent to that of the highest frequency.

The signal is always interfered with noise, makes the quality always poor. However, it is most sought as it can be transmitted to longer distances.

The AM radio transmitters can transmit sound waves with a frequency range of up to 15KHz. But the receiver can reproduce the signals only up to 5KHz or sometimes even Less. AM signal transmission and reception can be affected by external factors.

Storms and Sunspots can duly affect the signal quality, usually with a lot of noise in the background.

amplitude modulation

What is FM (Frequency Modulation)?

Frequency Modulation is the process by which the radio wave signal is transmitted by modulating the frequency. This method is considered to be the versatile modes of radio signal transmission and reception.

It is indeed a fact that the amplitude changes in FM also, however, it is not noticeable as in the AM. FM is most desirable for its signal quality.

The transmitter and receiver components are complex, thus making it expensive. The functionality of FM is also not that simple.

FM signals cannot travel long distances, for the fact that it requires many radio stations in between to receive and reproduce at every small distance. More importantly, FM consumes less power.

The geographical interference between two neighboring stations is also limited. Even the man-made interference of Cell phone towers and other towers is also considerably less, making the signal quality undisturbed.

FM transmission and reception requires very high bandwidth. FM is considered the premium broadcasting technologies which gives the perfect quality of sound.

FM radio stations sprung into action in the 1990s to offer high-quality music over the radio. The FM receiver accepts the correct transmitting station and rejects the unwanted signals, thus making it picture-perfect.

frequency modulation

Main Differences Between AM and FM

  1. The noticeable main difference between AM and FM is the disturbance factor, AM is a lot noisier and easily affected by external environmental changes whereas FM offers disturbance-free reception. AM has poor sound quality than the FM
  2. It is indeed to be accepted on the terms of an economy that AM radio signals can be propagated to a long distance without any need for intermediate radio stations, whereas FM cannot be transmitted to a longer distance and if done, it requires multiple stations to receive and reproduce.
  3. Another factor on the cost to be noted, AM transmitter and receiver components are simple and less expensive at the same time FM components are expensive.
  4. The technical difference in the modulation is, in AM the amplitude is modulated keeping the phase and frequency as constants, while in FM the frequency is modulated keeping phase and amplitude as constants.
  5. The bandwidth required by FM is more when compared to AM. FM requires twenty times more bandwidth than the AM.
Difference Between AM and FM



Both transmissions have their advantages. The factors may differ, as the usage differs from person to person and place to place.

For example, speech broadcasting prefers AM as the news is intended to reach a large population.

FM is preferred for music stations and broadcast. If cost comes into the picture, then AM can get the edge hands down.

For stereo sound, FM is chosen as it has a large number of sidebands. The current technology has made radio transmission and reception automated.

This has made the process simple and cost-effective too. Access to an international audience through radio signals is possible. The discoveries made in different eras for different purposes are entirely used in diversified areas.

Key Differences Between AM and FM (PDF Format)

Download the key differences in .PDF format, to read or print them later:

Difference Between AM and FM



  1. https://www.osapublishing.org/abstract.cfm?uri=ol-31-15-2254
  2. https://arxiv.org/pdf/1808.08589
  3. https://pure.tue.nl/ws/files/2235569/Metis174587.pdf
  4. https://apps.dtic.mil/docs/citations/ADA446837
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