FM FM microphone production tutorial circuit diagram

Wireless microphone Principle Analysis: The following is the circuit diagram of the FM wireless microphone, the circuit is very simple, no excess devices. High-frequency triode V1 and capacitors C3, C5, C6 form a three-point oscillator for a capacitor. For beginners, we temporarily do not wonder the specific working principle of capacitors. We just know that this circuit structure is a high-frequency oscillator. The load C4, L of the triode collector constitutes a resonator, the resonant frequency is the transmit frequency of the frequency frequency microphone, according to the parameter emission frequency of the element in the figure, between 88 to 108 MHz, just covers the reception frequency of the FM radio, by adjusting L Value (stretching or compression coil L) can easily change the transmit frequency and avoid the FM station. The transmit signal is coupled to the antenna by C4. R4 is the base bias resistance of V1, provides a certain base current to the triode, so that the V1 is operated in the zone region, and R5 is a DC feedback resistance, and the action of stabilizing the striking workpoint. The frequency modulation principle of such a frequency modulation microphone is to achieve the frequency modulation by changing the base and the emitter between the triode, when the sound voltage signal is applied to the base of the triode, the base and the emitter of the emitter of the emitter The size of the sound voltage signal is synchronized, while changing the transmit frequency of the triode, frequency modulation. The microphone MIC can collect the external sound signal. Here we use the electret small microphone, the sensitivity is very high, can collect weak sound, and this microphone must have a DC bias to work, and the resistor R3 can provide certain The DC bias, the larger the resistance of R3, the weaker the sensitivity of the microphone acquisition sound. The smaller the sensitivity of the microphone, the higher the sensitivity of the microphone, and the acoustic sound signal collected by the microphone is sent to the base of the triode after the C2 coupling and the R2 match, and the two diodes in the circuit are inverted in parallel, mainly a two-way limiting function. The diode is only 0.7V, and if the signal voltage exceeds 0.7V, it will be diversified by the diode, which ensures that the amplitude of the sound signal can limit between the positive and negative 0.7V, and the excessive sound signal will pass the triode. Modulation, resulting in sound distortion or even working properly. CK is an external signal output socket that can introduce a TV headphone socket or an external sound signal source such as a portable headphone socket into a frequency modulated transmitter through a dedicated cable, and the external sound signal is transmitted to the triode base after the R1 attenuation and D1, D2 limit. Extreme frequency modulation. So this kit can not only make a wireless microphone, but also make a TV wireless headset. The light-emitting diode D3 in the circuit is used to indicate the working state, and when the frequency-stroke microphone circuit is working, R6 is a current limiting resistor of the light emitting diode. C8, C9 is a power filter capacitor because the large capacitance is generally made of winding process, so the equivalent inductance is relatively large, and a small capacitor C8 can reduce the high-frequency internal resistance of the power supply, which is very common. In the circuit, K1 and K2 are actually a switch. It has three different positions. When all of the left is disconnected, the right side is K1, K2 is connected to the frequency band, the intermediate position is the K1, K2 is broken, Do wireless **, because the wireless ** device is used to use the microphone does not work, but the microphone will consume a certain static current, so the break K2 can reduce power consumption, extend the life of the battery.

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