RF power amplifier

This RF power amplifier outputs 2-3 channel signals, covering an area of ​​approximately one square kilometer, is an ideal device for opening a small TV launch station, suitable for electrochemical education. However, the local radio management committee should be reported when used, only after approval. Circuit work principle The power of the device circuit is shown in Figure 8.31. The variant tuning amplifier is formed by the triode BG1, BG2, BG3. The collector load of BG3 is the next input matching network, which avoids self-excited and the signal transmission gain is maximized. BGL, BG2, BG3 work in a status. BG4 focuses on high frequency dynamic characteristics, working in the ClassA, high efficiency, its base uses a self-contained negative bias circuit, which is advantageous to improve the temperature stability of the triode. The output of BG4 is a matching network that is efficiently transmitted to the transmit antenna. The whole machine is powered by a negative power supply. The C7-C10 is used as a central capacitor and is used as a power supply. Component selection and production BGL, BG2 is selected from high, low-frequency small power triode, such as 3DG30C or 9018, and the like. BG3 is selected for 2G711 and other medium power triodes, FT> = 500MH. , IC = 50mA, PCM = 500MW. The BG4 is selected for 3DA37 or MRF517 and other triodes, requiring ft> = 500 MHz, PCM> = 1W. The coils used in the circuit are all empty core coils. Ll, L2 is covered with a diameter of 0.97 mm on a circular pencil lever, and taps on the 3 circle of the ground. L3, L4 uses a diameter of 1.3 mm to paint the tin to remove the tin on the colored pen, and 6 turns is repeated to 150mm. L6, L7 uses a diameter of 1.3 mm to paint tin after plating tin on the colored pen. The 3 laps is repeated to 7mm, and the L5 is laminated on the pencil rod in a diameter of 0.77 mm. The RFC coils used were in a diameter of 0.41 mm in a 1 / 2W, 1.5K resistance, and 10 wrapped around 16 turns. The printing plate of this machine uses double-sided epoxy resin copper plate, a welded element; the other side and ground joints are shielded. When welding, the component pin is short, and the strength and resistance of the solder sheets of the variable capacitors are taken. The capacitor is non-grounded to support the support point, and the component is suspended, and the variable capacitor cartridge is grounded. All triodes use a flower basket pick-on-law to prevent high frequency self-excitement. After welding all components, install the separator and shield, and then load the core capacitor on the side of the shield box, welding high frequency blocking ring. When debugging, first adjust the DC operating point of the triode. The inter-stage coupling capacitor is disconnected, and the voltage meter is respectively adjusted on the emitter resistance of DG1 to BG3, respectively, respectively, respectively, indicate the voltage meter: BG1: E is 15V, BG2: E Extreme 1.0V, BG3: E is extremely 1.3V. Connect the coupling capacitor and load, turn on the power, such as self-excitement, fine-tuning the fine-tunable capacitor to eliminate. Then, the 2 or 3 channel RF signal output from the recorder is then connected to the input of the amplifier, while the capacitor is fine-tuned, and the image on the TV screen is observed. First disconnect the third level. The 75 ohm antenna is connected to the second level output, adjust C1, C2 to make the image of the TV, and then connect to the third and fourth level, and connect the antenna to the output. Reduce the supply voltage, adjust C3, C4, so that the BG4 collector current is maximum, adjusting C5, C6, so that the BG4 collector current is minimized. Finally, put the TV to the distance, fine tune the C1 ~ C6, make the image clear, the sound is bright, the color is the most colorful. This amplifier is only applicable to a video recorder having a RF output of 2 to 3 channels, and the radio is recorded for other channels, and the player needs to first modulate the video and audio signals on the 3 channel to the amplifier. (Transferred from China Electronic Production Website)

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