Chapter 4: Radio and Television
Define Modulation and explain its necessity in communication. (4 Marks)
Definition: The process of placing a low-frequency information signal onto a high-frequency carrier wave for long-distance transmission.
Antenna Height: Higher frequencies allow for much smaller, practical antenna sizes.
Interference: Prevents signals from different stations from mixing together.
Range: Increases the distance the signal can travel without fading.
Quality: Reduces the effect of noise and improves reception clarity.
Explain the Block Diagram of a TV Receiver. (4 Marks)
Tuner/RF Section: Selects the desired station channel and amplifies the weak signal from the antenna.
Video Detector: Separates the sound signal and the picture signal from the carrier.
Video Amplifier: Strengthens the picture signal before sending it to the Picture Tube/Display.
Sound Section: Processes the audio signal and sends it to the Loudspeaker.
Scanning/Sync: Ensures the picture is drawn on the screen correctly in sync with the transmitter.
Compare LED, LCD, and OLED Display Technologies. (3 Marks)
LCD: Uses liquid crystals and a fluorescent backlight (CCFL); slower response time.
LED: Uses liquid crystals but uses LEDs for backlighting; more energy-efficient and thinner than LCD.
OLED: Every pixel emits its own light (organic material); no backlight needed; provides the best contrast and "true blacks."
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