Linear coil, intermediate frequency trap coil, frequency compensation coil for audio frequency, wave blocking coil, etc.
1. Oscillating coil of transistor radio: This oscillating coil, together with the variable capacitor in transistor radio, forms a local oscillator circuit for generating a local oscillator signal 465kHz higher than the radio signal received by the input tuning circuit. Its exterior is a metal shielding cover, and its interior is composed of a nylon lining frame, an I-shaped magnetic core, a magnetic cap and a needle seat. I-shaped iron core is wound with high-strength enameled wire. The magnetic cap is installed on the nylon frame in the shielding cover and can rotate up and down. The inductance of the coil can be changed by changing its distance from the coil. The internal structure of the intermediate frequency trap coil of TV is similar to that of the oscillating coil, except that the magnetic cap can adjust the magnetic core.
2. Line oscillating coil for TV: Line oscillating coil was used in early black-and-white TV. It forms a self-excited oscillation circuit (three-point oscillator or intermittent oscillator, multivibrator) with peripheral resistance-capacitance elements and linear oscillation transistors, and is used to generate a rectangular pulse voltage signal with the frequency of 15625HZ.
There is a square hole in the center of the magnetic core of the coil, and the line synchronization adjustment knob is directly inserted into the square hole. By turning the line synchronization adjustment knob, the relative distance between the magnetic core and the coil can be changed, thus changing the inductance of the coil, keeping the line oscillation frequency at 15625HZ, and generating synchronous oscillation with the line synchronization pulse sent by the automatic frequency control circuit (AFC).
3. Line linear coil: Line linear coil is a kind of nonlinear magnetic saturation inductance coil (its inductance decreases with the increase of current), which is generally connected in series in the loop of line deflection coil, and its magnetic saturation characteristics are used to compensate the linear distortion of the image.
The linear coil is made of enameled wire wound on an I-shaped ferrite high-frequency core or ferrite bar, and an adjustable permanent magnet is installed beside the coil. By changing the relative position between the permanent magnet and the coil, the inductance of the coil is changed, so as to achieve the purpose of linear compensation.