AM TRANSMITTER
A transmitter is an equipment used to generate and amplify an RF (Radio Frequency) Carrier signal, modulate the carrier signal with intelligent signal and radiate the modulated RF carrier to the space.
CHARACTERISTICS OF TRANSMITTERS:
- Generate a carrier signal of appropriate desired frequency
- Provide some form of modulation which causes the information signal to modify the carrier signal.
- Provide enough power amplification to ensure that the signal level is so high as to carry the desired distance
MODE OF OPERATION OF AM TRANSMITTER.
It is made up of two stages: AF & RF Stages.
The Crystal Oscillator:
This is responsible for the generation of RF carrier signal or carrier frequency.
BUFFER AMPLIFIER:
It increases or amplifies the generated signal from the crystal oscillator before it will now be modulated.
At the Audio frequency stage, the audio signal from the microphone is amplified with audio amplifier. And then the AF Power Amplifier will boost the audio signal and make it suitable for the modulation stage.
For the RF stage, the RF carrier wave is obtained from a stable crystal oscillator and the buffer amplifier isolate the oscillator from the amplifier stage ( This is done to gain high stability)
In a broad sense, the microphone converts the audio signal into the message signal which is processed and filtered to make it occupy the required bandwidth .
The AF power amplifier boost, the voltage level of the processed message signal. The modulator provides enough power for the modification of the carrier signal.
The RF portions of the transmitter starts with the carrier oscillator which provides the required carrier signal frequency.
The buffer amp is a linear class A type that does the pre-amplification of the carrier signal and raises the power level high enough for modulation. The modulation of the occupied carrier signal takes place at the modulation amp.
RF output Amp stage which has to be a class C Amplifier for high Efficiency.
(Stay tuned for the complete Block Diagram and More explanation from STALITE ENGINEERING, thanks.)
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