Block Diagram of Monochrome TV Transmitter | New Topic

In this note, we are going to know the Block Diagram of Monochrome TV Transmitter or Black and White TV Transmitter. Welcome to Poly Notes Hub, a leading destination for engineering notes.

Author Name: Arun Paul.

What is Monochrome TV Transmitter?

A monochrome TV transmitter is an electrical device that sends television signals in black and white (grayscale) without color information. It transforms video and audio streams into modulated radio waves that are subsequently transmitted at a specified frequency for reception by television receivers. The system contains components for visual signal processing, synchronization, modulation, and transmission. It was commonly utilized in early television transmission prior to the introduction of color television.

Key Components on the Block Diagram of Black and White TV Transmitter

• Camera Tube
• Scanning and Sync Circuits
• Blanking and Sync Pulse Generators
• Video Amplifier
• Microphone
• Audio Amplifier
• RF Carrier Generator and Audio Modulator
• Combining Bridge
• and Transmitting Antenna

Monochrome TV Transmitter Working Principle

A monochrome TV transmitter works by capturing a scene in shades of gray with a monochrome TV camera. The collected image is subsequently transformed into an analog video signal that includes brightness (luminance) changes. To transmit this video stream, amplitude modulation (AM) is applied to a high-frequency carrier wave. Meanwhile, the audio signal captured by a microphone is processed independently and manipulated using frequency modulation (FM). The modulated video and audio signals are then mixed and broadcast via an antenna as radio waves. At the receiving end, a television demodulates the signals to rebuild the black-and-white video and sounds.

Block Diagram of Monochrome TV Transmitter

Here we have attached a monochrome TV transmitter block diagram with explanation –

• Camera Tube: Converts intensity of light from a scene into electrical variations, called video signal by using a photosensitive target plate.
• Scanning and Sync Circuits: Electrical current is extracted from the photosensitive target of the camera tube with the help of a scanning beam which is produced by sawtooth currents through horizontal and vertical deflection coils.
• Blanking and Sync Pulse Generators: The start of a sawtooth or sweep current signal is triggered by pulses called sync pulses. The retrace is blanked by blanking pulses and these pulses are periodic and appear for the specified time by using a monostable multivibrator.
• Video Amplifiers: Video signals along with blanking and Sync Pulses, called composite video signals are amplified by using wideband RC coupled amplifier circuits. The RF carrier generator and video modulator are radio frequency modulated by the video signal. Modulation is of Vestigial sideband (VSB) type AM to save the bandwidth. In this type of modulation, one sideband is vestiged to a small fraction of the whole band. In a TV, the lower sideband is vestiged and the upper sideband are carrier are sent in full.
• Microphone: It converts sound pressure variations into electrical variations, called audio signals .
• Audio Amplifiers: These amplify the weak audio signals.
• RF carrier Generator and Audio Modulator: A Radio frequency carrier is generated and is frequency modulated by the audio signals at low level. The radio frequency is then multiplied and amplified to the full level for transmission.
• Combining Bridge: Video modulated and audio modulated signals pass through a combining bridge (also called diplexer circuit) to go to a common transmitting antenna. The bridge prevents audio modulated signals from going to video sections and vice versa to avoid overloading.
• Transmitting Antenna: Video modulated signals and audio modulated signals are fed to the common transmitting antenna which radiates out the modulated signals into space in the form of electromagnetic waves. The antenna is omnidirectional in the horizontal plane.

Applications of Monochrome TV Transmitter

There are many applications of monochrome TV Transmitter –

• Used in old black and white television broadcasting
• Used in CCTV and low cost video transmission system
• Used in educational projects
• and also used in experimental projects in communication engineering.