Uncommonly used homemade home TV circuit diagram

◆Circuit overview

Many families now have household appliances such as televisions, VCDs, video recorders, game consoles, and even video cameras and DVDs. If the RF radio frequency signals of the above-mentioned home appliances are forwarded by a TV signal transmitter, and can be received and watched by TV sets with a radius of about 30 meters (within the range of the family room), it can save many inconveniences such as cable connections, and more can be achieved. The TV signal repeater is like a small home TV station for viewing on two sets of TV sets in different rooms. What is introduced below is this kind of TV signal repeater, which has the characteristics of simple circuit, low cost, and easy production.

◆Working principle

The circuit is shown in the figure below: The working principle of this circuit is that the RF signal is sent to the high-pass filter composed of C1, L1 and C2 through the 75 ohm RF cable, and the frequency below 45MHz is filtered out, and then passed through the transistor 9018, etc. The preamplifier is amplified and sent to upc1651 by capacitor C3 for power amplification, and its output signal is emitted through a whip antenna of about 60cm. 7805 and other components form a voltage regulator and power indicator to provide 5V power supply for upc1615.

◆Material selection and production

UPC1651 is a high-gain high-frequency amplifier integrated circuit, 9018 is a low-noise ultra-high-frequency transistor, and C1, L1, and C2 form a high-pass filter with a cutoff frequency of 47MHz. The capacitors are all high-frequency ceramic capacitors. The resistors are ordinary carbon film resistors. IC2 and other components provide 5V power supply and power indication. L1 is made on a cylinder with a diameter of 3mm and densely wound with 0.2mm enameled wire for 16 turns. The antenna uses a 60cm whip antenna. Because this machine works in the ultra-high frequency band, When designing and manufacturing printed circuit boards, the configuration of components and the length of leads must meet the requirements of high-frequency design. Try to keep the welding wires as short as possible and close to the circuit board. Infinite Electronics Production Network is designing this circuit They all use miniaturized components and can be installed in the 47x33x16mm plastic box provided by this site. The power supply uses a 9V DC regulated power supply, which does not take up much space when placed in a room or living room. Friends who have multiple TVs at home and cannot communicate with each other through signal lines can refer to the production.

◆Debugging and molding

This transponder circuit can also be placed in a small iron box, or in a discarded VHF high-frequency head. As long as the mechanical and electronic components are removed, it becomes a shielded box. Because the transponder circuit is simple, There are very few components. You can solder the components directly on the circuit board, and make sure the connections are correct and the welding is correct! The working current of the whole machine is about 25MA. The working current of 9018 is about 5MA, which can be adjusted through R1. Home appliances such as video recorders and VCDs The RF output cable should be a 75-ohm coaxial cable, the length should be as short as possible, and fully shielded (including the connector), which can reduce interference from the RF antenna. As long as the quality of the components is guaranteed, the transmitter can work normally.