Wu Hanqing Because the sensitivity of the FM radio is much higher than the sensitivity of the TV. Some user boxes do not have 88-108MHZ bandpass filters. The function of the transponder is to filter the signal output by the FM interface again, and then amplify it and transmit it through the open circuit for FM radio reception. The circuit of the transponder is shown in Figure 2. Considering that some user boxes have no bandpass filter or FM output but the filtering effect is not good, the input terminal of the transponder is composed of L1-L3 and C1-C3 88-108 bandpass filter can be Suppress out-of-band signals, improve the performance indication of the amplifier, and reduce the generation of combined frequencies. The special integrated circuit UPC1651 for pre-amplifier TV antenna amplifier, its main parameters are typically: VCC = 5V, ICC = 20MA, NF = 5.5DB, KP = 20DB, the highest operating frequency is 1.2GHZ. The main amplifier stage uses BFR91A. In order to increase the maximum output level and avoid the operating point from entering the non-linear area, the operating current of BFR91A should be made slightly larger, here 30MA. The probability gain of the whole machine is about 30DB. L4 and L5 are series resonant circuits, which also function as a band-pass filter. Component selection and installation and debugging C1-C8 all use ceramic dielectric capacitors, T uses 220V / 12V, 2VA or so small power transformer. L1-L5 are all wound with 0.51mm enameled wire to form a single-layer reborn coil of φ4MM, L1, L3, L4 are wound 16 turns, L2 is wound 5 turns and 20 turns. The TX uses a common rod antenna, and the remaining components can be selected according to the parameters shown in Figure 2. The printed circuit board is shown in Figure 3. During installation, the feet of the components should be shortened and soldered to the printed board. UPC1651 and BFR91A can be directly soldered on the copper foil surface. After the installation is completed, turn on the power of the amplifier. The VCC of IC1 should be about 5V, otherwise, the resistance of R1 should be changed appropriately to adjust. The working current of VT should be about 30MA. When the deviation is large, it can be adjusted by changing the resistance of R2. Send the FM signal to the input terminal of the transponder with the radio frequency line, use the FM radio to receive an FM signal near the center frequency point 98-108MHZ as far as possible, shorten the antenna length and pull a certain distance to make the signal slightly noisy Toggle L1-L4, adjust the inductance by changing the length of the antenna to minimize the noise in the radio, so as to ensure that the band pass filter has good operating characteristics in the frequency range of 88-108MHZ, if you can use the scanner Debugging, the effect will be better. Finally, the antenna of the transponder is elongated, and there should be a satisfactory listening effect in the range of 20M. Follow WeChat Download Audiophile APP Follow the audiophile class related suggestion '+ data.data.username +' '; dom + ='
Car Cable Harness, also known as a wire harness, cable assembly, wiring assembly or wiring loom, is an assembly of electrical cables or wires which transmit signals or electrical power. The cables are bound together by connector, terminal, cable ties, sleeves, electrical tape, conduit, PVC tube, corrugate tube, string, or a combination thereof.
Commonly used in automobiles, as well as construction machinery, cable harnesses provide several advantages over loose wires and cables. For example, many aircraft, automobiles and spacecraft contain many masses of wires which would stretch over several kilometres if fully extended. By binding the many wires and cables into a cable harness, the wires and cables can be better secured against the adverse effects of vibrations, abrasions, and moisture.
Car Wire Harness,Wiring Harness,Car Electrical Wiring Harness,American Autowire Mustang Harness Dongguan YAC Electric Co,. LTD. , https://www.yacenter-cn.com Cable TV FM signal transponder Urban TV system transmits several sets of FM stereo programs in the frequency range of 88-108MHZ while transmitting TV programs. There are two TV and FM output ports on the taxi user box as an output port. Among them, FM is the FM stereo output interface. Since most FM radios do not have an output interface, they can only be received by an antenna. Even if you try to connect the FM output of the user box to the radio input terminal with an RF cable, it ca n’t be moved. Inconvenient, so the vast majority of households have not used the FM signal resources in the cable TV, resulting in a waste of signal resources. Working principle Figure 1 shows the internal block diagram of the cable TV user box. After the input cable TV signal passes through the splitter, the main circuit outputs TV signals, and the branch outputs the FM signal through the bandpass filter, and the branch outputs the TV signal. The FM signal is output through the bandpass filter. The signal output from the branch is usually about 10DB smaller than the main output signal. This is 
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[Photo] Cable TV FM signal repeater (UPC1651)
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