Schematic Diagram 250mW FM transmitter electronic circuit

Posted on Feb 5, 2014

This FM transmitter electronic project works in FM band and it has a transmission power around 250mW. This FM transmitter electronic circuit is very simple and is based on some common transistors and electronic parts. T1 transistor can be a BC107, BC171 or equivalent, and is used as an small audio preamplifier that amplify the audio signal from t

Schematic Diagram 250mW FM transmitter electronic circuit
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he microphone. Adjusting the R2 variable resistor, audio signal level from the input ( microphone ) can be adjusted until will be delivered to the T1 preamplifier (an over amplified signal applied to T1 can produce an overmodulation). From T1, signal is delivered to T2 which form an Hartley oscillator (frequency of this oscillator depends of C8, C9 and L1). The transmitter frequency oscillator works in FM band 87. 5-108 MHz and can be set, adjusting C8 capacitor and L1 coil. L1 coil must have four turnings on a 0. 8-1 mm cylinder support with a 6 mm diameter (space between each wire must be around 1 mm ).

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