Wireless microphone circuit diagram
This wireless microphone is very suitable for beginners, and can easily achieve the same quality as the veteran. It has been successfully installed in guitars, because many people require high-power and high-sensitivity FM microphones, so Harry Lythall designed this new microphone circuit (version 5), and the frequency is constant It is also relatively high, and theoretically it can reach a distance of 1 km,
A 10dB high-frequency buffer and an audio amplifier are added to this line.
Many of the problems often found in the production of wireless transmitters are the production of coils. This production L1
The coil is helical with 3.25 turns, and the coil is directly made in the circuit board, so there is no need to make another coil. The two BC547 transistors can be replaced by any type of small signal NPN transistors such as 2N2222, etc .. The terminal BC557 is also a general-purpose crystal. If you want to change the input to an active microphone, you must remove the 4.7K resistor.
The actual distance determined by the designer's test is 700 meters, and the effect is really good. The configuration of the parts is as follows:
The size of the PC board is 50mm * 25mm, please adjust the size by copier or image processing software,
Pay attention to the reverse when exposing.
The finished picture is as follows:
As for how to adjust the frequency?
In the picture above, you can see a small secret device connected across the 12P capacitor of the circuit. This small device can adjust the capacitance in small amounts, so the frequency of the transmission can be adjusted slightly in the circuit. This device is only two Twisted insulated single-core wires, about 2 cm long, if you want to increase the capacitance (decrease the frequency), twist it a few more times. Cut it a bit shorter and use this method to adjust the frequency. Thanks again to Harry Lythall.
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