The amplifier feeds either an internal speaker or headphones. In a self-contained radio receiver for audio, the signal from the detector after the tuner is run through a volume control and to an amplifier stage. Still later, phase locked loop methods were used, with microprocessor control. This system shifts the radio frequency of interest to a fixed frequency so that it can be tuned with fixed-frequency band-pass filter. Modern radio tuners use a superheterodyne receiver with tuning selected by adjustment of the frequency of a local oscillator. A later method used a potentiometer supplying a variable voltage to varactor diodes in the local oscillator and tank circuits of front end tuner, for electronic tuning.
Often several sections would be provided on a tuning capacitor, to tune several stages of the receiver in tandem, or to allow switching between different frequency bands.
FREEWARE RADIO TUNER MANUAL
Older models would realize manual tuning by means of mechanically operated ganged variable capacitors. Combined with a detector, also known as a demodulator (diode D1 in the circuit), it becomes the simplest radio receiver, often called a crystal set. This creates a resonant circuit which responds to an alternating current at one frequency. The simplest tuner consists of an inductor and capacitor connected in parallel, where the capacitor or inductor is made to be variable. Inductively coupled crystal radio receiver The verb tuning in radio contexts means adjusting the receiver to detect the desired radio signal carrier frequency that a particular radio station uses. Subcarriers are then processed like real radio transmissions, but the whole bandwidth is sampled with an analog-to-digital converter (A/D) at a rate faster than the Nyquist rate (that is, at least twice the IF frequency).Ī tuner can also refer to a radio receiver or standalone audio component that is part of an audio system such as a hi-fi or stereo, to be connected to a separate amplifier. These are transmitted inside the receiver as an intermediate frequency (IF).
use a wider frequency bandwidth, often with several subcarriers. More complex transmissions like PAL/ NTSC (TV), DAB (digital radio), DVB-T/ DVB-S/ DVB-C (digital TV) etc. Broadcast FM/ AM transmissions usually feed this intermediate frequency (IF) directly into a demodulator that converts the radio signal into audio-frequency signals that can be fed into an amplifier to drive a loudspeaker. Luxman T-240L stereo FM tuner (top) and L-235 amplifier (bottom)Ī tuner is a subsystem that receives radio frequency (RF) transmissions, such as FM broadcasting, and converts the selected carrier frequency and its associated bandwidth into a fixed frequency that is suitable for further processing, usually because a lower frequency is used on the output.
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