English: Drawing of an IF (intermediate frequency) transformer with the front surface of the shield can cut away to show the transformer itself. An IF transformer is a resonant transformer used as a bandpass filter in the intermediate frequency section of a superheterodyne receiver. It consists of two windings of fine wire (flat cylinders) around a tube containing an adjustable powdered iron slug core. Each winding has an adjustable mica capacitor (top) connected across it to make a resonant circuit. The two resonant circuits are adjusted so their resonant frequencies are equal to the intermediate frequency of the receiver. The resonant transformer has a much higher Q factor than an ordinary resonant circuit, and is responsible for the selectivity of the receiver, allowing through a narrow band of frequencies from the desired radio station and rejecting nearby stations. Several IF transformers are used in the typical superheterodyne. The aluminum can surrounding it shields nearby stages from its electromagnetic field, preventing feedback which can cause parasitic oscillations