BA1404 5W FM Transmitter Circuit

Four components of the FM transmitter (C9018)


Circuit with a few components, only four to form a miniature wireless FM microphone, a more stable operating frequency, firing range of more than 10 meters, 1.5V supply, the current less than 0.5mA, so that the microphone energy also rare, 3V supply when the distance of up to 30 meters.
Circuit shown in Figure, BG and L and the transistor junction capacitance high-frequency oscillator circuit composed of transistor junction capacitance of about 2 ~ 3P, make the FM frequency falls within the scope of the coil should be 5mm in diameter around the core 7 of a circle, then by the condenser microphone modulated with a frequency of vibration when the signal generator frequency offset, to achieve FM. The emission current distance and the size of the emission control work, the resistance can not come too big nor too small, between 300 and 500 in Europe, less than 1 mW power.
BG when selected, the pipe must be greater than fT 300MHz, such as high frequency with 2SC3358 tube, the frequency is more stable, longer distance will be more. Inductance L divided into two coils around the system, but to be the same around, L1 0.5mm enameled wire with a diameter of 5mm in diameter and 4 turns around the skeleton, L2 3 turns around. Antenna can be 10cm long soft wire, use hand to touch the antenna will affect the frequency of changes. When used at a fixed location is very stable.

This circuit can be put into such a small ink bottle, the kit can be installed in the pen, battery or more small batteries A13, but note that a small-capacity battery plus a switch.





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1 Response

  1. hearing aids 2011/07/04 at 06:24:56

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