In this note, we will Explain Block Diagram of Monochrome TV Receiver. Welcome to Poly Notes Hub, a leading destination for engineering notes for diploma and degree engineering students.
Author Name: Arun Paul.
What is Monochrome TV Receiver?
A monochrome TV receiver is a television that can only display images in one color (typically grayscale or black and white). It was the first type of television technology before color TV became popular. Monochrome televisions were popular until the 1960s, but they were progressively displaced by color television. However, they are still employed in specialized applications such as night vision monitors, medical imaging, and scientific instruments.
Key Components of Monochrome TV Receiver or in the Black and White TV Receiver Block Diagram
- Receiving Antenna
- Tunner
- IF Stages
- Video Detector
- Video Amplifier
- Deflection Stage
- Picture Tube
- Frequency Amplifier
- FM Detector
- Audio Amplifier
- Loudspeaker
Monochrome TV Receiver Working Principle
A monochrome television receiver receives and processes television signals to produce black-and-white visuals. The process begins with an antenna or cable receiving broadcast signals that include both visual and audio data. The tuner picks the appropriate channel, and the demodulator decodes the video signal.
The video amplifier improves the brightness (luminance) information while disregarding the color data. This processed signal is then directed to the cathode ray tube (CRT), where an electron beam scans the screen in a predetermined pattern. The strength of the beam varies based on the brightness information, resulting in various shades of gray on the screen.
Simultaneously, the audio stream is split and transmitted to the speaker system for output. The image is continuously refreshed at a fast speed, resulting in smooth animation. This complete procedure allows a monochrome television to display clear black-and-white images from transmitted signals.
Explain Block Diagram of Monochrome TV Receiver
The basic elements of a monochrome TV receiver are shown in Fig and this is the monochrome TV receiver block diagram –
- Tuner and IF Stages: The receiver is a superheterodyne receiver to achieve high selectivity and high gain. In a superheterodyne receiver, the radio frequency signal, duty amplified by a pre-amplifier, is mixed nonlinearly with the oscillations of higher frequency but of fixed amplitude, generated by a local oscillator. The output of the mixer consists of several intermodulation products, one of which is a signal having a frequency equal to the difference of frequencies of the two signals. The difference frequency is called intermediate frequency, which is selected and amplified. The advantages of the superheterodyne technique are better selectivity and higher gain.
- Video Detector and Trap Circuit: The amplified IF goes to the video detector which recovers video signal from the modulated wave and feeds it to the video amplifier for amplification through the trap circuit, which prevents the video signal from entering into the audio channel.
- Video Amplifiers: These are wideband RC coupled amplifiers. The amplified video signal goes to the picture tube.
- Picture Tube: The video signal varies the strength of the electron beam. This beam strikes the phosphor dots on the fluorescent screen which glow, the intensity of the glow is proportional to the intensity of the video signal.
- Deflection Stages: The phosphor dots glow in quick succession from left to right and top to bottom with the help of scanning currents in the deflection coils. The synchronizing pulses, recovered by the detector, trigger the scanning circuits which produce deflection currents, duly synchronized with the scanning currents used in the transmitter. The deflection currents go to the deflection coils to deflect the electron beam horizontally and vertically on the fluorescent screen to reproduce the picture.
- Sound Section: It consists of a sound IF(SIF) amplifier, FM detector, audio amplifier, and loudspeaker. The difference in frequency between frequency-modulated IF and video carrier IF is called intercarrier frequency, second IF, or sound IF. It is received from the video detector and passes to the SIF amplifier through a trap circuit, which prevents the SIF signal from going into the video amplifier. The FM detector detects the audio signal which is then amplified by audio Amplifiers. The amplified signal goes to the loudspeaker which converts it into sound. Thus, the original sound is reproduced.