am transmitter circuit

Posted on Feb 4, 2014

Here is the circuit diagram of a simple AM transmitter circuit that can transmit your audios to your backyard. This circuit is designed with limited power output to match the FCC regulations and still produces enough amplitude modulation of voice in the medium wave band to satisfy your personal needs. You will love this!. The circuit has two parts,

am transmitter circuit
Click here to download the full size of the above Circuit.

an audio amplifier and a radio frequency oscillator. The oscillator is built around Q1 (BC109) and related components. The tank circuit with inductance L1 and capacitance VC1 is tunable in the range of 500kHz to 1600KHz. These components can be easily obtained from your old medium wave radio. Q1 is provided with regenerative feedback by connecting the base and collector of Q1 to opposite ends of the tank circuit. C2, the 1nF capacitance, couples signals from the base to the top of L1, and C4 the 100pF capacitance ensures that the oscillation is transfered from collector, to the emitter, and through the internal base emitter resistance of the transistor Q2 (BC 109), back to the base again. The resistor R7 has a vital part in this circuit. It ensures that the oscillation will not be shunted to ground trough the very low value internal emitter resistance, re of Q1(BC 109), and also increases the input impedance such that the modulation signal will not be shunted to ground. Q2 is wired as a common emitter RF amplifier, C5 decouples the emitter resistance and unleashes full gain of this stage. The microphone can be electret condenser microphone and the amount of AM modulation can be adjusted by the 4. 7 K variable resistanceR5.

Leave Comment

characters left:

Related Circuits

  • New Circuits



    Popular Circuits

    Test Signal Generator
    Selectable sensitivity Preamplifier
    Crystal oscillator-doubler
    Automatic Arming Auto Alarm
    amplifier Amp measures board twist (unfortunately!)
    Control an Amplifier With a SqueezeBox
    IR Remote Control Tester
    Simple Field Strength Meter
    Optical Receiver Circuits
    The pulse width detection circuit 555
    Electronic bio-wave therapy device