Keywords: Homemade UPC1651 TV transmitter
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Circuit Overview There are now many families with TV, VCD, recorders, game consoles, and even household appliances such as cameras and DVDs. If the RF radio signal of the above home appliance is forwarded, the TV of about 30 meters of the supplier circle (within the home room range) is received, and the connection to the cable can be saved and many more inconvenience, can also The aircraft is watching in different rooms, which seems to be a small family TV station. The following is the characteristics of such a TV signal repeater, which has the characteristics of simple circuit, low cost, easy production. ◆ Working principle circuit is shown in the figure below: This circuit's working principle is that the radio frequency signal is sent to a high pass filter composed of C1, L1, C2, which will be below 45MHz. Then The pre-amplifier composed of triode 9018 and the like is amplified by the capacitor C3 to the UPC1651 for power amplification, and the output signal is transmitted out of the whip antenna of about 60 cm. 7805 and the like constitute a voltage indication of the power supply to the UPC1615 to supply 5V power supply.
◆ Making material Making UPC1651 is a high gain high frequency amplification circuit, 9018 is a high-pass filter with low noise ultra-high frequency triode, C1, L1, and C2 constitute a cutoff frequency of 47 MHz. Capacitor is selected to high frequency porcelain capacitor. Electrical resistance ordinary carbon Membrane resistance .ic2 and other components provide 5V power supply and power instructions. The production of L1 is on a cylinder of 3 mm in diameter, and the 16 turns is subjected to 16 turns with 0.2 mm lacquered wire. The antenna uses 60cm whip antenna. Due to this machine High frequency band, when designing printed boards and production, all of the configuration and leads of the element meet the requirements of high-frequency design, so that the welding line is ultra short, to close the circuit board, unlimited electronic production network in design are used when the section size of the circuit elements may be mounted in a plastic box site provides a 47x33x16mm. The power supply uses 9V DC regulated power supply, placed in the room or the living room, do not take much space, there are several TVs in the home and unable to interoperate the signal line can refer to the production. ◆ Debugging this transponder circuit can also be placed in a small iron In the case, it can also be placed in a waste 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, the components are small, the components can be directly soldered in the circuit. On the board, and ensure that the connection is correct, welding is not wrong! The whole machine operating current is around 25mA. The operating current of 9018 is around 5mA, and can be adjusted by R1. Video recorder, VCD, radio frequency output cable, 75 ohms, coaxial, etc. The cable is as short as possible, using full shield [including joint portions], which can reduce the interference of the RF antenna. As long as component quality assurance, the transmitter can work properly.
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