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The power of an AM radio signal plotted against frequency. fc is the carrier frequency, fm is the maximum modulation frequency. In radio communications, a sideband is a band of frequencies higher than or lower than the carrier frequency, that are the result of the modulation process. The sidebands carry the information transmitted by the radio ...
Amplitude modulation (AM) is a modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave.In amplitude modulation, the amplitude (signal strength) of the wave is varied in proportion to that of the message signal, such as an audio signal.
FM receivers employ a special detector for FM signals and exhibit a phenomenon known as the capture effect, in which the tuner "captures" the stronger of two stations on the same frequency while rejecting the other (compare this with a similar situation on an AM receiver, where both stations can be heard simultaneously).
Illustration of the spectrum of AM and SSB signals. The lower side band (LSB) spectrum is inverted compared to the baseband. As an example, a 2 kHz audio baseband signal modulated onto a 5 MHz carrier will produce a frequency of 5.002 MHz if upper side band (USB) is used or 4.998 MHz if LSB is used.
DRM+, a different system based upon the same principles of HD Radio on the FM band, but can be implemented in all the VHF bands (1, 2, and 3), [41] either as a hybrid analog-digital or digital only broadcast, but with 0.1 MHz digital-only bandwidth, it allows 186.3 kbit/s data rate [42] [43] (compared to HD FM with 0.4 MHz allowing 300 kbps.)
A radio band is a small frequency band (a contiguous section of the range of the radio spectrum) in which channels are usually used or set aside for the same purpose. To prevent interference and allow for efficient use of the radio spectrum, similar services are allocated in bands.
Hybrid digital broadcast systems, which combine (mono analog) AM transmission with digital sidebands, have started to be used around the world. In the United States, iBiquity 's proprietary HD Radio has been adopted and approved by the FCC for medium wave transmissions, [ 93 ] while Digital Radio Mondiale is a more open effort often used on the ...
In the 1950s, several AM stereo systems were proposed (including the original RCA AM/FM system which later became the Belar system in the 1970s) but the FCC did not propose any standard as AM was still dominant over FM at the time. 1960: AM stereo first demonstrated on XETRA-AM, Tijuana, Mexico, using the Kahn independent sideband system.