Simple short range portable FM transmitter circuit diagram

Posted on Feb 5, 2014

This is a simple 2N2222 transistor based radio FM transmitter circuit within the FCC (Federal Communications Commission) limit, that is no license is necessary for using thisstable FM transmitter circuit. What is an FM transmitter FM stands for Frequency Modulation andFM transmitter is a radio frequency (RF) transmitter which uses frequency modul

Simple short range portable FM transmitter circuit diagram
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ation of audio signals. Frequency modulation means that the frequency of a carrier signal is changed according to the input audio signal. The portable FM transmitteris able to transmit sound or music to any standard radio FM receiver. The range of this transmitter is near to 120 meters. Audio signal is applied via a condenser micro phone, which is a capacitive sound sensor. Simplicity and portability makes this transmitter circuit superior to other FM transmitters. The transmission frequency of this FM transmitter can be adjusted using the variable capacitor C7. The main applications of this circuit includesFM transmitter for car, walky talky, wireless audio transmitteretc. The signal from the condenser microphone is passed through a coupling capacitor C1 and amplified by transistor Q1, which acts as a pre amplifier. The amplified signal is applied to the base of transistor Q2. R2 and R6 provide necessary biasing to the amplifier transistor Q1 (2N2222). Amplified sound signal will be available at the collector of Q1 and it coupled to the base terminal of transistor Q2 via the capacitor C3 and R4. Q2, C7 and the inductor forms a RF oscillator circuit that operates in the 80 to 130 MHz range, which is voltage controlled oscillator so its frequency can be modulated by the input audio signal.

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