Small home video transmitter circuit made with UPC1651

◆Circuit Overview Many families now have household appliances such as televisions, VCDs, video recorders, game consoles, and even 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 can also provide more The TV signal repeater is like a small home TV station to watch 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. ◆The working principle 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 lower than 45MHZ is filtered out, and then passed through the high-pass filter. The preamplifier composed of transistors 9018 and others is amplified and sent to upc1651 by capacitor C3 for power amplification, and its output signal is emitted through a whip antenna of about 6 inches. 7805 and other components form a voltage regulator and power indicator to provide 5V power supply for upc1615. ◆Material selection: upc1651 is a high-gain high-frequency amplification integrated circuit, 9018 is a low-noise ultra-high-frequency transistor, 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 Membrane resistor, 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 6-inch whip antenna. Because this machine works in In the ultra-high frequency band, when designing and manufacturing printed boards, the configuration of components and the length of leads must meet the requirements of high-frequency design. ◆The transponder circuit can be placed in a small iron box for debugging and molding, or it can be placed in a A discarded VHF high-frequency head. As long as the mechanical and electronic components are removed, it becomes a shielded box. Since the transponder circuit is simple and has few components, the components can be soldered directly to the circuit board and the connections must be ensured. Correct, 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. The RF output cable of home appliances such as video recorders and VCDs should be 75 ohm coaxial cables, and the length should be as short as possible. Use full shielding [including the connector] to reduce interference from the RF antenna. As long as the quality of the components is guaranteed, the transmitter can work normally.