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How tuners work

Introduction

A tuner is an adjustable device which passes one radio frequency, or band of frequencies, and excludes others, by using electrical resonance. The simplest tuner consists of an inductor and capacitor. Combined with a detector, also known as a demodulator, it becomes the simplest radio receiver, often called a crystal set.

Tuners can be either stereo or mono, and are available for TV, FM, and AM signals.

Typically, AM and FM tuners are sold with built-in amplifiers and/or loudspeakers, and this device is referred to as a receiver. However, standalone stereo FM tuners are sought after for audiophile and TV/FM DX applications, especially those produced in the 1970s, when standards of quality were higher before plastic replaced metal. A few 1970s tuners feature now-deprecated Dolby noise reduction for FM broadcasts.

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Uses of radio for audio

Audio AM broadcast radio sends music and voice in the Medium Frequency (MF -- 0.300 MHz to 3 MHz) radio spectrum. AM radio uses amplitude modulation , in which louder sounds at the microphone causes wider fluctuations in the transmitter power while the transmitter frequency remains unchanged. Transmissions are affected by static because lightning and other sources of radio add their radio waves to the ones from the transmitter.

FM broadcast radio sends music and voice, with higher fidelity than AM radio. In frequency modulation , louder sounds at the microphone cause the transmitter frequency to fluctuate farther, the transmitter power stays constant. FM is transmitted in the Very High Frequency (VHF -- 30 MHz to 300 MHz) radio spectrum. FM requires more radio frequency space than AM and there are more frequencies available at higher frequencies, so there can be more stations, each sending more information. Another effect is that the shorter radio waves act more like light, travelling in straight lines that are not reflected back towards the Earth by the ionosphere , resulting in a shorter effective reception range. FM receivers are subject to the capture effect , which causes the radio to only receive the strongest signal when multiple signals appear on the same frequency. FM receivers are relatively immune to lightning and spark interference.

FM Subcarrier services are secondary signals transmitted "piggyback" along with the main program. Special receivers are required to utilize these services. Analog channels may contain alternative programming, such as reading services for the blind, background music or stereo sound signals. In some extremely crowded metropolitan areas, the subchannel program might be an alternate foreign language radio program for various ethnic groups. Subcarriers can also transmit digital data, such as station identification, the current song's name, web addresses, or stock quotes. In some countries, FM radios automatically retune themselves to the same channel in a different district by using sub-bands.

Commercial services such as XM and Sirius offer digital Satellite radio .