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Simple small radio experiment I once got a six-lamp radio at my friend's house, and after disassembling the machine, I assembled a small radio station with 6Pl power amplifier tubes. The circuit is shown in the figure below: B1, B2, G, R1, R2, C2, C3, C4 and C5 are all disassembled products. Because the volume of the power supply filter capacitor in the machine is too large, a color TV filter capacitor is used. L1 selects 22mm enameled wire to wrap 100 turns on the magnetic ring of MX-2000. L2 determines the radio frequency of the station. If the frequency is selected in the middle wave band, L2 can use 35mm enameled wire on the medium wave magnet bar for 30 + 50 turns, or use 13mm enameled wire tightly wound 90 turns on the 25mm paper tube. In this way, the transmission frequency will fall between 550-1650kHz. If the short wave band is selected, L2 can be wound 9 turns between the 16mm paper tube with 0.5mm enameled wire. The frequency of the oscillator thus constructed falls between 6 and 18 MHz. C5 is an air duplex, and its capacity is 360pFx2. B1 is the original power transformer. For high voltage part rectification, 4 IN4007 are used. B2 is the original output transformer. C2, C3, mica capacitors disassembled inside the machine, C2, C3 withstand voltage is better than 400V. R1, R2 can also buy cement resistance. Because the scattered power is large, its power should be ≥IW. TX is a 1/4 antenna, which can be replaced by a thick wire, the length is about 1/4 of the emission wavelength. The author chose 3mm and 8m long enameled wire. The whole circuit installation does not need to use copper-clad board, directly use a piece of glue board, drill on it. Hole, can be welded by scaffolding. As long as the components are good, the circuit will start to oscillate after installation. When oscillating, a light blue electron flow can be seen in the G, accompanied by a "sizzle" sound. If there are conditions, a simple field strength meter can be made to adjust the R2 to maximize the transmitted field strength. The antenna can be mounted vertically on the wall via insulators. After connecting the antenna, input an audio signal of about 5W at B2 to extend the distance between a radio and the transmitter. The radio should receive the signal clearly and the distortion should not be obvious. If the hum is too loud when launching, Grounding can solve it. After actual measurement, the transmission power is as large as 4.5W, so the relevant regulations of the National Non-Committee must be followed during the experiment. ![]()
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