What type of circuit is used to tune a radio?

Answer 1

Superheterodyne I think.....

Answer 2

Some place in your radio there's an oscillator or a more sophisticated thing called a synthesizer which generates an alternating current. The output of either one is mixed with the incoming signal and for example, the difference between the two goes to a tuned circuit which filters it and amplifies it. The circuit that filters and amplifies only does so for a narrow fixed frequency (intermediate frequency). As the oscillator is varied, the difference between the incoming signals and the oscillator that are the same as the intermediate frequency are the ones that get passed on to following stages in the radio.

Answer 3

I think Eugene has it right. The incoming AM radio signal (Amplitude Modulation on an assigned FCC carrier frequency) passes to a VARIABLE CONDENSER and inductance in parallel, which constitute a tuning circuit. (The tuning circuit fortifies a particular frequency and attenuates others.)

This frequency is then mixed with an internally generated signal-frequency so that the difference frequency (intermediate frequency, carrying all the original information of the carrier) can be subsequently amplified. (FWIW I think that in the distant past this intermediate frequency was 455 kilocycles/kilohertz; and it may still be that.)

The idea of having a difference frequency be what is amplified (as opposed to just amplifying the carrier frequency) is that the subsequent amplifier stages in your radio can focus on amplifying one frequency instead of having to cope with all the frequencies in the AM radio spectrum.

Answer 4

At the rudimentary level it is a variable capacitor that cuts out or notches frequencies. Much like a tone control cuts out the highs leaving only the lows.