Production amplitude wireless microphone

The usual electronic enthusiasts learn and practice make the frequency modulated microphone, which describes a modulated wireless microphone circuit, the transmit frequency is in the medium wave section, and the signal can be received with a medium wave radio. Working principle: BG1 or the like constitutes a common base capacitor three-point oscillator. The adjustment L1 can make the output frequency change between 800 kHz to 1000 kHz. The oscillating signal is sent to the base of the BG2 as the carrier signal, and the audio signal from the microphone is bacter. The BG4 is enlarged after R10, and the base of the BG2 is also sent as a modulation signal. Since the BE of the BG2 has a nonlinear characteristic, the amplitude modulation of the audio signal on the carrier signal can be realized. The modulation signal obtained by the emitter of the BG2 is passed by C6, The matching network composed of L2 and R5 is connected to the antenna, emitting electromagnetic waves to the space. W Used to adjust the size of the modulation signal, prevent overmodeling. Component selection and debug L1, L2 is the oscillation coil of the medium wave radio, 1, 6 ends of the LTF-2-3 oscillation coil, can also be in the middle of the radio The skeleton is made of φ0.08 mm enameled wire through 85 turns. The microphone can be used in the microphone. The switch uses a micro switch and a power supply 9V stacking battery. The antenna is used for the appropriate length of the soft line. The remaining element is shown in the picture. Debugging. When the R6 is adjusted first, so that the collector current of the BG4 is 4mA. Tune the frequency caliper of the modulated radio to an 800kHz to 1000kHz range no broadcast signal, and then make the radio close to the wireless microphone, facing the elective The physical microphone speech, adjusts L1, L2 to allow the radio to receive the signal. Then pull the distance between the wireless microphone and the radio, adjust the L1, L2 to the strongest signal received by the radio. At the same time, adjust W to the received signal Distortion, and the transmitted power is the largest. The circuit is installed. It is sealed in one square box and the microphone is connected with a coaxial shield.

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