Circuit Overview
Many families now have a TV, VCD, recorder, game conso, and even a home appliance such as a camera and a DVD. 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
The circuit is shown in the figure below: The working principle of this circuit is that the radio frequency signal is sent to a high pass filter composed of C1, L1, C2, which will be below 45MHz, and then pass through the triode 9018, etc. The composed preamplifier is amplified by the capacitor C3 to the UPC1651 for power amplification, and the output signal is transmitted out of a 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
The UPC1651 is a high-frequency amplifier integrated circuit, 9018 is a high-pass filter having a low noise ultra-high frequency transistor, C1, L1, and C2 constitute a cutoff frequency of 47 MHz. Capacitance selects high frequency porcelain capacitors. Electrical resistance uses ordinary carbon film resistance. IC2 and other components provide 5V power supply and power instructions. The production of L1 is on a cylinder having a diameter of 3 mm, and the 16-circle is subjected to a 16-circle. The antenna is a 60cm whip antenna. Due to the machine work in a super high frequency section, When designing printed boards and production, the length of the component and the length of the lead must 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 this circuit The miniaturization element is used, and can be installed in the 47x33x16mm plastic box provided by this site. The power supply uses a 9V DC voltage regulator power supply, and it is placed in the room or the living room. There are many TVs that have multiple TVs in the home can be made by friends.
Debugging
This transponder circuit can also be placed in a small iron box, and it can 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, There are very few components, can be sold directly on the circuit 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. Recorder, VCD and other home appliances The RF output cable should be selected for 75 ohm coaxial cable. The length is as short as possible, using full shield [including joint portions], which can reduce the interference of the RF antenna. As long as the component quality assurance, the transmitter can work.
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