Intermediate frequency transformer (commonly known as mid-cycle) is a special kind of transformer with fixed resonant circuit in superheterodyne transistor radio, but the resonant circuit can be fine-tuned in a certain range to achieve a stable resonant frequency (465 kHz) after connecting to the circuit. Fine tuning is accomplished by changing the relative position of the magnetic center.
The medium frequency transformers in radio are mostly monotone, simple in structure and occupy less space. Because of the low input and output impedance of the transistor, in order to match the input and output impedance of the transistor, there are primary taps and secondary coupling coils with few cycles. The advantage of dual tuning is that it has better selectivity and wider passband, and is mostly used in high-performance radios.
Two-stage IF amplifiers are usually used in transistor radios, so three mid-cycles are needed to couple and transmit the front and back signals. BZ1, BZ2, BZ3 and other symbols are commonly used in practical circuits. In use, they can not be arbitrarily changed in the circuit position.
