With the further development of digitization and networking, various programs and traffic stations, which are mainly live broadcasts, have sprung up like mushrooms after a rain, and the demand of the audience and the extension of the broadcast time require uninterrupted, high-speed FM transmitters. Quality and long-term work. TF520-10 kW FM transmitter is a series of transmission equipment of Beijing Broadcasting Film and Television Equipment Factory.
1. The working principle of TF520-10 kW FM transmitter
The TF520-10 kW FM transmitter can work at any frequency between 87-108 MHz, and the output power of 10 kW is output by two identical 5 kW power amplifiers after power synthesis. Each 5 kW power amplifier is composed of 5 identical 1 kW amplifier units through power distribution and synthesis network. Each 1 000 W unit is synthesized and output by 4 350 W basic amplifying units via the network. The 300 W boost power amplifier is also the same as the 350 W basic amplifier unit of the 1,000 W unit. The entire 10 kW transmitter is designed for broadband, which is convenient for maintenance and unified spare parts, making it easy to master the machinery and equipment.
2. Power supply method of TF520-110 kW FM transmitter power amplifier
The DC power supply of 300 W and 1 000 W power amplifiers is 48 V, and the power supply of each chassis of the switching power supply will not affect each other to improve the reliability and safety of power supply. The power supply temperature rise fan can automatically turn on and off according to different temperatures. It protects the fan and switch tube, and has surge protection from overcurrent and overvoltage. The short-circuit protection circuit adapts to the large fluctuations of the power supply network, which is much better than centralized power supply, reduces the large current centralized power supply, improves the reliability and utilization of the power supply, reduces power failures, and improves the broadcast rate.
3. The working principle of 5 kW power amplifier
3.1 Power synthesis of 5 kW power amplifier
Two 5 kW power amplifiers use 3 dB directional coupler power synthesis. One of the failures caused the power to drop by 6 dB and the broadcast can still be maintained. Because of the output power of the 3 dB directional coupler.
If one of the 10 1 kW power amplifiers is damaged, one 5 kW is N=5 and the other 5 kW is M=4. That is, one single arm output is 5 kW, and the other output is P0=(M2/N)Pλ=(42/5)Pλ=16/5=3.2 kW. The three combination is 5+3.2=8.2 kW, which can maintain low power output, creating conditions for uninterrupted broadcast and television. If there is a phase difference at the output end, a filter can be connected to the input end before distribution. Correct the phase vector.
3.2 Monitoring of each power amplifier unit
The power supply voltage, current, incident power, reflected power, temperature, unbalanced power, etc. of each power amplifier unit can be displayed on the screen with corresponding readings. At the same time, the relevant data is sent out through the computer via the RS232 interface for monitoring and protection. The exciter adopts Italian R． VR. The company’s 30 W exciter can automatically switch between main and standby when using dual excitation and send it to the 300 W power amplifier host.
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