Two tube FM FM wireless microphone transmit circuit making

The emission frequency of this unit is in 88 to 108 MHz. It is set to have a strongest point. The emission distance is greater than 100m, and the power consumption is small, and a 10-digit battery can also be used. All components can be installed on small circuit boards of 3 cm × 1 cm. In the figure, the BG and peripheral components constitute a capacitance three-point oscillator, which causes the audio voltage generated by the MIC to change the bump capacitance of BG1, and in the high frequency, even small capacitance changes can cause a large frequency offset. The FM signal is sent to the antenna emission by BG2. BG1, BG2 can be used 3DG201, 3DG6, etc., β> 80. The capacitance in the circuit uses a small porcelain capacitor. The resistance adopts 1 / 8W small resistance, and the L1 uses the ∮ 0.6mm enameled line to the bead pen onto a 7 turn, taken at the 3 turn, and then add a television in a television. Spiral magnetic heart (also available The short-wave radio is magnetic core, but the effect is slightly poor), and the L2 is used in the wounds of the beads to go abound around the ball with a ∮ 0.35mm. The antenna can use 80mm long soft wire, for convenience, the short line of the multi-shade core wire. If the device is assembled in the figure, it is generally not necessary to adjust. Turn on the FM radio, adjust the FM band and L1 magnetic core to a certain noise disappearance.

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