Tuner (radio)
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A tuner is an adjustable device which passes one radio frequency, or band of frequencies, and excludes others, by using electrical resonance. A tuner performs the process of selecting the desired signal but it's output is not directly usable and must be sent to another device. Typically tuners are sold with built-in audio amplifiers, loudspeakers, and/or a video display to form a radio receiver or television set. Tuners can be either stereo or mono, and are available for TV, FM, AM, and other types of radio signals.
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.
Standalone stereo FM tuners are sought after for audiophile and TV/FM DX applications, especially those produced in the 1970s, when performance standards were among the highest. A few 1970s tuners feature now-deprecated Dolby noise reduction for FM broadcasts. In some instances the tuner may be modified to improve performance.[1]
VHF/UHF TV tuners are rarely found as a separate component; however cable boxes serve as a separate tuner, and have channel 3/4 outputs so they can serve as a cable-ready emulator for TVs that aren't cable-ready, and often feature composite, S-video, or component video outputs so they can be used on video monitors that do not have a TV tuner, or ones whose tuner is not working. They are usually bundled with a monitor, VCR, and/or PVR. However, they do exist for use by members of the television industry, and may be purchased on Internet Auction Sites, such as eBay.
TV tuners are also installed on PCI computer expansion cards (or in USB device, or even as a part of video card), together with a DSP, allowing a personal computer to display and/or capture television channels. A number of earlier models were stand-alone tuners, designed to deliver TV picture through a VGA connector. This allowed viewing television on a computer display, but, of course, did not allow recording programmes by the PC.
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[edit] Transmitting tuner
Another type of radio tuner sometimes known as an antenna tuner allows a transmitter to be efficiently operated with antennas and transmission lines that are not matched in impedance. Such a tuner is useful when operating an antenna system over a wide range of frequencies.
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