Miniature wireless microphone transmitter

The miniature transmitter is a simple single tube frequency modulated wireless microphone circuit. It is characterized by the oscillation coils and the transmitted antenna, the launch efficiency is high, and it is not easy to run without interference, suitable for long time. The transmitter is only suitable for placing a fixed location to make a wireless microphone, which is not suitable for hand-held use. Otherwise the oscillation frequency is susceptible to the body's impact. Below is the transmitter circuit: The circuit is powered by a 1.5V battery, consuming from about 2 to 3 mA, so the button battery is used, the body can be done. Since the annular antenna L1 for the emission is partially as an oscillation coil, the antenna flows is high frequency: current synchronous with the oscillating cheek, so it is always at the optimum launch state. The transmit frequency is convenient to receive the conventional FM radio band. When using a high sensitivity receiver, the emission distance can reach more than one hundred meters (empty), The fabricated ring antenna is produced: a metal ring or a square frame is made of a coated line with a length of 160 mm and a diameter of 1 mm, an embedded casing. Debug: Adjust the capacitor C3 so that the transmit frequency falls between the FM band between 88-108MHz to facilitate reception with the FM radio. When debugging, do not close to the launch antenna, do not close to the metal, so as not to affect the oscillation frequency and the emission distance. The triode must use a super high frequency tube, otherwise it affects the emission efficiency and distance, the 2SC3355 ultra-high frequency tube used here, the feature frequency is 6.5 GHz, and the power consumption is 600MW. The microphone Mickey should use a high sensitivity of the elective microphone, which can be selected by the multimeter.

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