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Block Diagram & Working Principle of Superhetrodyne Radio Receiver

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The Superhetrodyne circuit is used in almost all the transistor radios. In this type of circuit the frequency of incoming signals is changed into a fixed frequency known as 'Intermediate Frequency IF'. The main work of amplifying the signal and selecting the desired station, is done in IF section. This permits higher amplification per stage and better selectivity.

The main component of circuit are:
1. Frequency Converter (Mixer and Oscillator)
2. I.F. Amplifier
3. Detector
4. Audio Pre-amplifier
5. Driver
6. Output
7. Power Supply


1. Frequency Converter (Mixer and Oscillator) It has two section Mixer and Oscillator. Usually only one transistor is used for both section. The Oscillator produces oscillations at a frequency, which is higher than the frequency of the station being received. The difference equals to the intermediate frequency.
Out of the signals intercepted by the aerial, a tuned circuit used at the input of the mixer stage selects the signals from the desired stat…