Ultra-small cable TV amplifier

Cable TV networks have become popular, but due to the limitations of their lines, some users often cannot get high-quality signals, resulting in unsatisfactory TV image signals. The author has made a small and easy-to-use cable TV amplifier using a small number of components. The amplifier has the characteristics of few components, simple circuit and high efficiency. Working principle: The circuit is shown in the figure above. The amplifier consists of two parts: an amplifier circuit and a power supply. The core of the amplifier is a Japanese-made ultra-high frequency linear amplifier circuit. The outer line is packaged using the microwave device production process. It has a small size, a wide working frequency band and a good amplification effect. The amplified signal is input by capacitor C1. Due to the good high-frequency response of the IC, its gain can reach 20dB, so the output signal effect is good. The power supply part consists of transformer T, high-frequency choke L1 and filter capacitor C7. It is added to the output end of the amplifier through a 75Ω coaxial cable. After the secondary AC power supply is rectified by diode VD2, C4, R1, C3 and VD1 form a filter voltage regulator circuit, and R2 and VD3 form a light-emitting indication circuit. Production instructions: In the circuit, the IC model is µPC1651. The voltage regulator VD1 has a voltage value of 4.9V~5.6V/0.5W, and 2CW53 can also be used. The rectifier VD2 can be 1N4001, 2CP16, etc. VD3 can be a Ø3mm light-emitting tube. Except for capacitors C3 and C4, the remaining capacitors are high-frequency ceramic capacitors. Inductor L1 uses Ø0.5mm enameled wire, which is wound 20 turns on the Ø4mm drill bit. T uses a small power transformer (3W-4W), and the secondary voltage is 6V. Sockets X1 and X2 are both 75Ω coaxial cable sockets. The amplifier and power supply parts of the amplifier should be installed in a shielding box respectively. The shielding box is made of thin copper or iron sheet with a thickness of 0.2-0.3mm. The ground wire of the shielding box should be in reliable contact to obtain good shielding. The output and input impedance of the amplifier is 75Ω, and it is led out of the shielding box with a high-frequency cable. The high-frequency cable uses SWY-75-5-1 or SS75-5-4 special cables. It is not advisable to use shielded cables with multiple core wires because they have large high-frequency losses, which affects the use effect.