How to Design and Make Antenna Control Interlocking Protection Device

“In order to protect the safety of TV transmitter equipment and ensure the safe and high-quality broadcast of TV programs, it is necessary to design and manufacture an antenna control interlocking protection device. This paper expounds the design, installation and use of the antenna control interlocking protection device in the author’s unit. Practice has proved that the device has played an effective protective role on the transmitter and provided a favorable guarantee for safe operation and safe broadcasting.

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In order to protect the safety of TV transmitter equipment and ensure the safe and high-quality broadcast of TV programs, it is necessary to design and manufacture an antenna control interlocking protection device. This paper expounds the design, installation and use of the antenna control interlocking protection device in the author’s unit. Practice has proved that the device has played an effective protective role on the transmitter and provided a favorable guarantee for safe operation and safe broadcasting.

Both R/S TV transmitters and HARISS TV transmitters are internationally advanced TV transmitters in quality and technology. Mengshan Broadcasting is equipped with three German R/S TV transmitters, one of which is used for Shandong Satellite TV programs. The host of the transmission, and the original HARISS TV transmitter used for Shandong Satellite TV programs as a backup machine, the configuration of Mengshantai Shandong Satellite TV program transmitters should be considered first-class. The reliability and safety of other auxiliary equipment of the transmitting system, such as the antenna feeder system, power distribution system and antenna control system, must also be matched. The safety protection measures of the coaxial switch for the main and standby transmitters and antenna switching are very necessary for safe and high-quality broadcasting. For example, the transmitter and antenna switching device must have safety protection measures and technical requirements. First, when the antenna is switched, it is not inverted. When the transmitter is working, the transmitter cannot be turned on; the second is that the transmitter is not allowed to switch the antenna manually, automatically or by mistake. In order to protect the safety of the transmitter equipment, an antenna control interlocking protection device is designed and manufactured.

1. Status Quo and Transformation Ideas of Transmitter Interlocking Interface

Shandong Satellite TV program TV transmitter adopts 1+1 mode, the main transmitter is R/S TV transmitter, HARISS TV transmitter is used as backup transmitter, the host and backup machine use coaxial switch to share a set of antenna feeder system for transmission. The antenna status of the R/S TV transmitter has a dynamic working diagram on the CCU screen. It is necessary to connect the antenna status to the CCU interface. There is an antenna (or load) in-position interlock interface in the transmitter control box. The antenna we made An antenna status interface is provided on the controller, and the antenna in-position interlocking protection function is realized by connecting it. However, there is no function of inverting the antenna during startup, and no interface is provided for sampling the working state of the transmitter. The power supply switch is not a traditional AC contactor, but a logic control and Electronic switch circuit. It is relatively advanced, and it is a new device. It is not easy to take samples from the internal circuit modification of the device. If the sample is taken from the outside, the RF power represents the working state of the transmitter, and the other is the power supply current. The RF power monitoring port has not been found, and the cable head is also It is different from the common ones in the past, so we have to sample from the current parameter to realize the protection measure that the antenna is not allowed to be switched during the transmitter operation. The HARISS TV transmitter provides the function of the antenna status interlocking interface. You can directly connect the antenna status in the antenna controller to the transmitter interface. When the transmitter is working, the function interface that does not allow the antenna to be inverted is not provided. The start-up work is to control the AC contactor to pull in. There is no auxiliary contact on the AC contact, but the working state of the transmitter can be easily taken out, that is, the power is drawn from the AC contactor’s pull-in contact, and an AC 220V medium and small electromagnetic relay is installed. , take a group of normally closed contacts as the power-on state sampling.

2. Schematic diagram of TV transmitter power-on state sampling

1. R/S transmitter power-on state sampling schematic diagram

2. Schematic diagram of HARISS transmitter start-up state sampling and interlock control

3. Working Principle of R/S Sampling at Power-on State

In order to ensure the integrity of the R/S transmitter, the power-on state sampling as shown in Figure 1 above is adopted. The sampling circuit includes transmitter working current sampling, sampling current rectifying circuit, sampling current/voltage converting circuit, sampling voltage and reference voltage comparing circuit, and driving control circuit. When the transmitter is in standby, the input current of the three-phase AC wire is 2A, and the current of the three-phase AC wire is 32A when it is working at rated power. The current changes greatly when it is working at standby and at rated power. It can directly control the base of the switch tube Q1 from the output of DW1. In the sampling state, the sampling current point becomes larger (20A), the action point cannot be changed arbitrarily, and the control action is not sensitive (K pull-in or disconnection time is long), it is necessary to add an operational amplifier circuit to solve this problem. First make a bus-type current transformer, the wire diameter is 0.5mm insulated copper wire, and the number of turns is 50. Under normal circumstances, the load of the current transformer should not be too large, because the current is not too large and the coil turns are few, which is harmful to equipment and personnel. There are no adverse consequences. After the sampling current of the secondary terminal of the transformer is rectified by C1, C2, D1, D2, it is calibrated by the DW1 potentiometer, and then enters the non-inverting amplifier for voltage conversion. Make the output voltage less than the power supply voltage, enter the second-stage comparison operational amplifier, and adjust DW2 to change the current (power) start-up threshold. When the sampling voltage is higher than the reference voltage, pin 1 inputs a high level, the drive switch transistor is turned on, and the relay K is pulled in, indicating that the transmitter is turned on and working.

4. Working principle diagram of transmitter interlock control

In Figure 1, when K pulls in, its normally closed contact K-2 is used for sampling the R/S transmitter’s power-on state. Figure 2 shows the status sampling of the standby machine. When the transmitter is turned on, the KM pulls in, and the AC relay JC also pulls in. A group of normally closed contacts JC-1 is used for HARISS transmitter status sampling. When K or JC only has one action, its normally closed contact is disconnected, and the two groups of normally closed contacts are connected in series and then connected to the antenna control interlock control contact, so that the action of the antenna controller is invalid, that is, the antenna switching does not operate to protect the transmitter effect.

V. Conclusion

This transformation does not change any hardware circuit of the transmitter to ensure the integrity of the transmitter equipment. This equipment has no adverse effect on the original transmitter and is also safe for maintenance personnel. The transformation circuit is simple, and the transformation cost is less than 30 yuan. The function is feasible and reliable, can play a role in protecting the transmitter, and provide a favorable guarantee for safe operation and safe broadcasting.