A superheterodyne receiver is a type of radio receiver that uses frequency mixing to convert a received signal to a fixed intermediate frequency (IF) which can be more conveniently processed than the original carrier frequency.
The antenna collects the radio signal. The tuned RF stage with optional RF amplifier provides some initial selectivity, and may also serve to prevent strong out-of-passband signals from saturating the initial amplifier.A local oscillator provides the mixing frequency; it is usually a variable frequency oscillator which is used to tune the receiver to different stations. The frequency mixer does the actual heterodyning, it changes the incoming radio frequency signal to a higher or lower, fixed, intermediate frequency (IF).
The IF band pass filter and amplifier supply most of the gain and the narrowband filtering for the radio. The demodultor extracts the audio or other modulation from the IF radio frequency; the extracted signal is then amplified by the audio amplifier.