Question

Draw the block diagram of Amplitude Modulated (AM) Radio transmitter.

Answer 1

Amplitude Modulated (AM) transmitter
Fig gives the block diagram of amplitude modulated radio transmitter. It consists of two sections (i) Audio frequency (AF) section and (ii) Radio frequency (RF) section.
AF section
The AF section of the transmitter generates the modulating wave (signal). The conversion of sound energy into electrical energy is performed by the microphone.
The electrical energy available from the microphone is very low. Hence, it is amplified through an amplifier. The output from the AF amplifier if fed to the AF power amplifier. The power amplifier provides the required audio frequency power. The output of the AF power amplifier is given to the modulator. A modulator is an electronic circuit with transistor, and passive components, which performs the process of modulation.
RF section
In the RF section, the high-frequency carrier wave is generated by a crystal controlled oscillator. The output of the crystal controlled oscillator is power amplified by RF power amplifier. The buffer isolates the RF power amplifier from the oscillator. This arrangement keeps the frequency of the crystal controlled oscillator as a constant. In the modulator, the RF wave and modulating AF signal are mixed to produce the amplitude modulated wave. The output of this section is fed to the antenna for transmission.