| rdfs:comment
| - Amplitude modulation (AM) is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave.
- In the mid-1870s, a form of amplitude modulation—initially called "undulation currents"—was the first method to successfully produce quality audio over telephone lines. Beginning with Reginald Fessenden's audio demonstrations in 1906, it was also the original method used for audio radio transmissions, and remains in use today by many forms of communication—"AM" is often used to refer to the medium-wave broadcast band (see AM radio).
- The Iotians of Sigma Iotia II learned how to build AM radios with manuals left behind by the crew of the Horizon, a starship that visited the planet in 2168, before the prime directive was adopted by Starfleet. In 2268, Spock made use of an Iotian AM radio to communicate with the USS Enterprise after he and Leonard McCoy escaped the custody of Bela Okmyx. (TOS: "A Piece of the Action" ) Uhura detected AM and FM radio transmissions coming from the planet 892-IV in that same year. (TOS: "Bread and Circuses" )
- Amplitude modulation (AM) is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent. For example, changes in the signal strength can be used to specify the sounds to be reproduced by a loudspeaker, or the light intensity of television pixels. (Contrast this with frequency modulation, also commonly used for sound transmissions, in which the frequency is varied; and phase modulation, often used in remote controls, in which the phase is varied)
- Amplitude modulation, or AM, is a variation in the amplitude of a signal, according to the instantaneous value of a modulating signal. (Borrowing from radio terminology, the signal being amplitude modulated is usually referred to as the "carrier".) When the modulator is of subsonic frequency, the result is a slow or rapid variation in the volume level of the carrier signal which is referred to as tremolo. When the modulation is of audio frequency, the result is a composite waveform containing the original carrier, and new waveforms at sum and difference of the frequency of the carrier and the frequency of the modulator. (This assumes that the carrier and modulator are both sine waves; if not, then each harmonic present in either signal acts like a separate carrier or modulator.) These sum
|
| abstract
| - Amplitude modulation (AM) is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent. For example, changes in the signal strength can be used to specify the sounds to be reproduced by a loudspeaker, or the light intensity of television pixels. (Contrast this with frequency modulation, also commonly used for sound transmissions, in which the frequency is varied; and phase modulation, often used in remote controls, in which the phase is varied) In the mid-1870s, a form of amplitude modulation—initially called "undulatory currents"—was the first method to successfully produce quality audio over telephone lines. Beginning with Reginald Fessenden's audio demonstrations in 1906, it was also the original method used for audio radio transmissions, and remains in use today by many forms of communication—"AM" is often used to refer to the mediumwave broadcast band (see AM radio).
- Amplitude modulation, or AM, is a variation in the amplitude of a signal, according to the instantaneous value of a modulating signal. (Borrowing from radio terminology, the signal being amplitude modulated is usually referred to as the "carrier".) When the modulator is of subsonic frequency, the result is a slow or rapid variation in the volume level of the carrier signal which is referred to as tremolo. When the modulation is of audio frequency, the result is a composite waveform containing the original carrier, and new waveforms at sum and difference of the frequency of the carrier and the frequency of the modulator. (This assumes that the carrier and modulator are both sine waves; if not, then each harmonic present in either signal acts like a separate carrier or modulator.) These sum and diffferences frequencies are often not harmonically related to the carrier, and the results can be bizarre, particularly when complex waveforms containing many harmonics are used. Compare with frequency modulation. For some reason, audio-frequency AM is seldom implemented on commercial synths, although it is easy to do with a modular synthesizer. Caution! Math ahead... A basic mathematical equation for amplitude modulation is: A = (IG + M) * C where C is the carrier signal, M is the modulating signal, IG is an initial gain for the carrier (determines the relative modulation ratio at a given modulation amplitude), and A is the amplitude-modulated output signal. Ring modulation is simply a special case of this; setting the IG to zero simplifies the equation to: A = M * C which is ring modulation. This shows why, with a ring modulator, it is necessary for signal to be present at both inputs; if either M or C is zero, the result is zero. Also, the commutivity of multiplication explains how the carrier and modulation signals can be switched to the opposite inputs, and the result will be the same.
- The Iotians of Sigma Iotia II learned how to build AM radios with manuals left behind by the crew of the Horizon, a starship that visited the planet in 2168, before the prime directive was adopted by Starfleet. In 2268, Spock made use of an Iotian AM radio to communicate with the USS Enterprise after he and Leonard McCoy escaped the custody of Bela Okmyx. (TOS: "A Piece of the Action" ) Uhura detected AM and FM radio transmissions coming from the planet 892-IV in that same year. (TOS: "Bread and Circuses" ) In 2371, the crew of USS Voyager picked up an SOS on the AM radio of a 1936 Ford found adrift in space in the Delta Quadrant. (VOY: "The 37's") In 2376, the people of Kelemane's planet invented AM radio and attempted to contact the Voyager. (VOY: "Blink of an Eye")
- Amplitude modulation (AM) is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave.
- In the mid-1870s, a form of amplitude modulation—initially called "undulation currents"—was the first method to successfully produce quality audio over telephone lines. Beginning with Reginald Fessenden's audio demonstrations in 1906, it was also the original method used for audio radio transmissions, and remains in use today by many forms of communication—"AM" is often used to refer to the medium-wave broadcast band (see AM radio).
|
![[RDF Data]](/fct/images/sw-rdf-blue.png)