Posts Tagged ‘AM Transmitter’

AM-CW ham bands transmitter

This is a small transmitter is a good stable QRP transmitter, which has many uses, from the HF bands AM transmitter, radio control models, or AM / CW ham-band transmitter. Circuit is almost ridiculously simple, and construction is even simpler. It is basically a single transistor oscillator with very low output impedance, suitable for driving the base of another transitory stage amplifier. Oscillator uses a single coil and crystal. The coil is tuned to a frequency output, which may correspond to the crystal frequency, or harmonics.

Read Source: http://w1.859.telia.com/~u85920178/tx/cw-am_00.htm

AM Transmitter by BC109

The circuit is in two halfs, an audio amplifier and an RF oscillator. The oscillator is built around Q1 and associated components. The tank circuit L1 and VC1 is tunable from about 500kHz to 1600KHz. These components can be used from an old MW radio, if available. Q1 needs regenerative feedback to oscillate and this is achieved by connecting the base and collector of Q1 to opposite ends of the tank circuit. The 1nF capacitor C7, couples signals from the base to the top of L1, and C2, 100pF ensures that the oscillation is passed from collector, to the emitter, and via the internal base emitter resistance of the transistor, back to the base again. Resistor R2 has an important role in this circuit. It ensures that the oscillation will not be shunted to ground via the very low internal emitter resistance, re of Q1, and also increases the input impedance so that the modulation signal will not be shunted. Oscillation frequency is adjusted with VC1.
Q2 is wired as a common emitter amplifier, C5 decoupling the emitter resistor and realising full gain of this stage. The microphone is an electret condenser mic and the amount of AM modulation is adjusted with the 4.7k preset resistor P1.
An antenna is not needed, but 30cm of wire may be used at the collector to increase transmitter range.

Related Links Circuits
More circuit RF Transmitter
More circuit AM Transmitter
AM Micropower Transmitter
AM/FM/SW Active Antenna by MPF102
ZN414-MK484 Portable AM Receiver
FM Stereo Transmitter with IC BA1404
Ramsey 25 BA1404 Stereo FM Transmitter

AM Micropower Transmitter

The picture to the left is a high quality radio transmitter for the A.M. broadcast band. The transmitter legally operates with “micro-power” and will not set any distance records but, unlike simpler designs, the frequency stays put and the fidelity is excellent. Although the schematic looks somewhat complex, the circuitry is easy to build and adjust for experimenters with a little “tweaking” experience. A simple output meter confirms proper signal level and checks antenna tuning while “on the air”. Add an audio mixer, tape recorder, and perhaps a CD player and have a near-professional micro-power station.

Read more original source:

http://www.techlib.com/electronics/amxmit.htm