Description
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 , 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 tun-able 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 transferred 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.
Am Transmitter Circuit
Diagram with Parts List.
Am Transmitter Circuit
Diagram
Notes .
• The transmission frequency can be
adjusted using the variable capacitance C3.
• Use a 200uH inductor for the L1 in
the tank circuit.
• Power the circuit using a 9V battery
for noise free operation.
• Use a 30 cm long insulated Copper
wire as the antenna.
No comments:
Post a Comment