Showing posts with label am. Show all posts
Showing posts with label am. Show all posts
Monday, September 2, 2013
Simple AM Transmitter Circuit
Circuit Diagram:
Description
There are not many AM transmitters that are easier to build than this one because the inductor is not tapped and has a single winding. There is no need to wind the inductor as it is a readily available RF choke (eg, Jaycar Cat LF-1536). To make the circuit as small as possible, the conventional tuning capacitor has been dispensed with and fixed 220pF capacitors used instead. To tune it to a particular frequency, reduce one or both of the 220pF capacitors to raise the frequency or add capacitance in parallel to lower the frequency. Q1 is biased with a 1MO resistor to give a high input impedance and this allows the use of a crystal ear piece as a low cost microphone.
Friday, April 12, 2013
Simple AM Transmitter Circuit
AM
transmitter circuit that can transmit your audios to your backyard.This
circuit is designed with limited the 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.
transmitter circuit that can transmit your audios to your backyard.This
circuit is designed with limited the 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.
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.
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.
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.
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.
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