Amplitude modulation (AM) is a widely-used communication technique that involves varying the amplitude of a carrier wave in proportion to the information signal. This approach is commonly applied in radio broadcasting and other types of electronic communications, making it one of the earliest and most enduring methods of transmitting information over the airwaves.
In AM, a high-frequency carrier wave is combined with a lower-frequency message signal. The amplitude of the carrier wave fluctuates in direct relation to the message signal’s amplitude. This technique allows the original information—whether it’s an audio signal for radio broadcasts or a data signal for telecommunications—to be transmitted over long distances. At the receiving end, a demodulator extracts the original message signal from the modulated carrier wave, making it usable for playback, analysis, or further processing.
| Property | Description |
| Carrier Wave | A high-frequency signal that serves as the base for modulation. |
| Message Signal | The information to be transmitted, typically an audio signal in traditional radio broadcasting. |
| Modulation Index | The ratio of the message signal amplitude to the carrier amplitude, affecting the degree of modulation. |
| Sidebands | Frequency components generated above and below the carrier frequency, carrying the actual information. |
| Demodulation | The process of recovering the original message signal from the modulated carrier at the receiver. |
Amplitude modulation was first demonstrated in the early 20th century during pioneering experiments by inventors like Roberto Landell De Moura and Reginald Fessenden. By the 1920s, AM had become the dominant method for transmitting voice and music over long distances. As radio broadcasting grew in popularity, AM became a household staple, bringing news, entertainment, and cultural programming to millions.
Over time, as newer modulation techniques like frequency modulation (FM) and digital transmission methods emerged, AM’s prominence in certain domains diminished. Nonetheless, AM continues to play a crucial role in various communication scenarios.
| Application Area | Examples |
| Broadcasting | AM radio stations transmit music, talk shows, and news. |
| Aviation Communications | Aircraft use AM for voice communications on VHF airband frequencies. |
| Amateur Radio | Many amateur radio operators use AM and its variants for long-distance communication. |
| Shortwave Radio | AM is widely used for international broadcasting and long-range transmissions. |
| Telecommunications | Early telephone systems employed a form of AM to transmit voice signals over local loops. |
| Data Transmission | On-off keying (OOK), a basic form of amplitude-shift keying, uses AM principles to transmit digital data. |
Amplitude modulation remains a foundational technique in the field of electronic communications. Despite the rise of more advanced modulation methods, AM’s historical importance, simplicity, and continued use in certain applications ensure its place in the broader landscape of communication technologies. Whether it’s a vintage AM radio broadcast, a shortwave transmission, or a component of a modern data modulation system, the principles of AM continue to inform and inspire the way we transmit and receive information today.
There are 3 principal kinds of amplitude modulation. They are; Double sideband-suppressed service modulation (DSB-SC). Single Sideband Modulation (SSB). Vestigial Sideband Modulation (VSB).
Amplitude modulation (AM) is also widely used to modify a carrier wave to transmit statistics. For instance, in AM radio, the voltage (amplitude) of a service with a fixed middle frequency (the station's channel) is varied (modulated) through the analogue audio signal. AM is likewise used for digital information.
amplitude modulation (AM), a variant of the amplitude of a provider wave (generally a radio wave) according to the traits of a signal, which include a vocal or musical sound composed of audio-frequency waves.