Two Transistor FM Transmitter

An ultrasensitive FM transmitter using only two transistor is shown below.

two transistor radio

 The following shows the antenna of the FM transmitter along with 9V battery.

two transistor FM radio with antenna
 The following shows the schematic diagram of the FM transmitter. In this two transistor FM transmitter, a pre-amplifier is added which is formed by the Q2 transistor in the schematic below. The 2nd transistor used in the circuit which is Q4 is the RF amplifier. Both the transistor used here is general purpose 2N3904 transistor.

Two Transistor FM Transmitter

The audio signal enters the circuit via the electret microphone labelled MIC2. This audio signal is amplified by the pre-amplifier circuit made by the transistor Q2. The output from the per-amplifier enters the RF amplifier stage via the capacitor C13. The RF amplified signal is modulated using the LC tank circuit made by inductor L2 and variable capacitor VC2. The inductor is a 6 turn coil made by laminated copper wire of #20 gauge. The variable capacitor is from 10pF to 30pF(or 40pF). The modulated signal then goes to the antenna. The antenna is of wire of length 25cm.

To make better version one can use RF transistor like 2N3563 or 2SC945 for the RF stage. The circuit is powered by 3V battery(9V can also be used) which gives more power and durability than the previously shown one transistor FM transmitter. 

This FM transmitter is extension of the previously shown One Transistor FM Transmitter.

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