Carrier frequency in the context of Sideband

In electronics and radio, a tuner is a type of receiver subsystem that receives RF transmissions, such as AM or FM broadcasts, and converts the selected carrier frequency into a form suitable for further processing or output, such as to an amplifier or loudspeaker. A tuner is also a standalone home audio product, component, or device called an AM/FM tuner or a stereo tuner that is part of a hi-fi or stereo system, or a TV tuner for television broadcasts. The verb tuning in radio contexts means adjusting the receiver to detect the desired radio signal carrier frequency that a particular radio station uses. Tuners were a major consumer electronics product in the 20th century but in practice are often integrated into other products in the modern day, such as stereo or AV receivers or portable radios.

A superheterodyne receiver, often shortened to superhet, is a type of radio receiver that uses frequency mixing to convert a received signal to a fixed intermediate frequency (IF) which can be more conveniently processed than the original carrier frequency. Edwin Howard Armstrong developed the concept, though Lucien Lévy, Walter Schottky, Henry Round, and John Renshaw Carson worked along the same lines. Superheterodyne receiver systems are still a modern feature, and can be used for other modes than AM.

According to Nahin, "Any receiver that shifts the antenna signal frequencies to new locations in the spectrum is a heterodyne receiver." The prefix super is reserved for those receivers that include a tunable antenna filter for image rejection, and intermediate frequency amplification that suppresses adjacent channels. "This sort of receiver circuitry results in an easy-to-use radio that has reliably consistent tuning with a clearly audible audio output. It is the gold standard of modern AM broadcast radio."

Frequency deviation (${\displaystyle f_{\Delta }}$) is used in FM radio to describe the difference between the minimum or maximum extent of a frequency modulated signal, and the nominal center or carrier frequency. The term is sometimes mistakenly used as synonymous with frequency drift, which is an unintended offset of an oscillator from its nominal frequency.

The frequency deviation of a radio is of particular importance in relation to bandwidth, because less deviation means that more channels can fit into the same amount of frequency spectrum. The FM broadcasting range between 87.5 and 108 MHz uses a typical channel spacing of 100 or 200 kHz, with a maximum frequency deviation of +/-75 kHz, in some cases leaving a buffer above the highest and below the lowest frequency to reduce interaction with other channels.