After the antenna signal and the local oscillator signal are mixed, the IF signal is further selected by the IF transformer and then amplified by the next stage. The entire structure is installed in a metal shielding cover with lead pins at the bottom and adjustment holes at the top. The primary coil and the secondary coil are both wound around the magnetic core, and the magnetic cap is covered outside the magnetic core. There are threads on the magnetic cap and it can rotate on the nylon bracket. The inductance of the coil can be changed by adjusting the gap between the magnetic cap and the magnetic core.
IF transformers are generally matched with capacitors to form a tuning circuit. IF transformers are divided into single-tuning and double-tuning. A single-tuning IF transformer is only composed of a primary coil and a capacitor to form a tuning circuit. If the tuning circuits are coupled by capacitors or inductors, it is called a double-tuning IF transformer. Generally, transistor radios have three single-tuning IF transformers, and the positions of the three are not interchangeable.