Complex sentence: In such a radio receiver, a local oscillator is used to heterodyne or "beat" against the incoming signal frequency, generating sum and difference frequencies-one of these will be at the intermediate frequency or IF, and will be selected and amplified.
Split into simpler sentences: In such a radio receiver, a local oscillator is used to heterodyne or "beat" against the incoming signal frequency, generating sum and difference frequencies. One of these will be at the intermediate frequency (IF), and will be selected and amplified.