Radio receiver

As well put by Wikipedia, a radio raceiver has to perform three functions on the signal from the antenna:

filtering, so you can tune the the station you care about. This filters based on the frequency of the carrier wave you want. I.e. you use a bandpass filter.
amplification: otherwise you won't be able to hear anything if the emitter is too far away
demodulation: this means decoding the signal based on whatever way it was encoded, notably e.g. AM/FM

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