Make a CATV wireless transmitter with eliminated cable TV enlargement modules, CATV Wireless Transmitter
Keywords: making CATV wireless transmitter
Make a CATV wireless transmitter with eliminated cable TV amplification module
With the transformation of cable TV systems, upgrades and expansion, the original cable TV amplifier will face phase-out (because the original amplifier is low in the original amplifier, some is 450MHz, there is 300MHz, which makes the frequency more than 300MHz or more than 450MHz Cable TV programs will not be enlarged and transmitted). But almost all enlarged modules are imported modules, with Motorola, Philips, and Japanese electrical, and their technical indicators are first-class, and it is a pity. The author uses two Motorola 450MHz amplification modules to make a CATV signal wireless transmitter, with a TV set around 20m near the launch antenna, can wirelessly receive nearly 30 sets of CATV programs, and the image quality is good.
working principle
The schematic diagram of the circuit is shown in the drawings. The CATV signal is input from the IN input port. The C1 is coupled to the adjustable failure device ATT as gain adjustment (generally controlled the input signal at about 70 to 72 dBUV), then the C2 coupling into the 1 foot of the ICl, after ICI amplifying from 5 The foot output is then coupled into 1C2 1 foot, and the second signal is enlarged, and then output from the 5 pin of IC2, and then directly transmits the CATV signal from the antenna after being coupled to the antenna. The output level at the time of 110 dbuv . Since the two amplification modules are large at operation, in order to ensure that the three-end regulator set is not damaged, a triode expands the output current and the diode D5 from the voltage compensation. Since the output voltage of the tripathic stabilizing block is 0.7V by the transmitting junction of the triode BG, the diode D5 has a high output voltage pad of the three-terminal steady block to ensure that the output voltage is stable in 24V. 1C1, IC2, and power supply portions are shielded with metal cartridges before and after preparation, and then shield it with a large metal box to prevent self-motivation.
Second, debugging
When debugging, use a field strength to measure the IC2 output level, adjust the ATT, so that the IC2 output level is around 110dBUV. If there is no velody, a TV can be used to adjust to the CH7 channel, (176.25MHz) Then, then insert the indoor tie rod antenna and pull all the antennas, place the transmitter in a place where the TV is about 20m, the emission antenna is vertical with the ground (the transmit antenna can be replaced by a single television indoor tie rod antenna), so that the TV Clear.
The adjustable attenuator in this transmitter can be removed in the eliminated cable amplifier, and the numerical value of the remaining element is marked in the figure. At ICL, IC2, IC3, and BG should be installed enough heat sink to ensure proper circuit work. The transmitter is effective coverage of about 20m, but it will also be shortened by the room structure and climate effect, sometimes more than 20m. The wireless receiving TV program set is about 30 sets, less range of programs transmitted than 860MHz, 550MHz system, suitable for use in hostel, dormitory, and no cable TV lines.
Note: 1. All high-frequency capacitors in this circuit use quality porcelain capacitors, and the pressure is 1 kV.
Prevent Thunderstorm Tiantine or 220V City Electric Broadlight Circuit Damage IC1, IC2. ICL. 1C2 is the Motorola 450MHz CATV amplification module. 2. The power supply transformer B is a high quality transformer above 30VA.
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