Lesson Notes By Weeks and Term v4 - SHS 3
ELECTRONIC COMPONENTS AND CIRCUITS
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ELECTRONIC COMPONENTS AND CIRCUITS
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Applied Technology
Class: SHS 3
Term: 2nd Term
Week: 20
Grade code: 2.5.2.LI.12
Strand code: 4
Sub-strand code: 2
Content standard code: 2.5.2.CS.1
Indicator code: 2.5.2.LI.12
Theme: ELECTRICAL AND ELECTRONIC TECHNOLOGY
Subtheme: ELECTRONIC COMPONENTS AND CIRCUITS
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This lesson introduces the fundamental principles behind AM (Amplitude Modulation) and FM (Frequency Modulation) radio receivers. Radio is a vital part of our daily lives in Ghana, from listening to the morning news on Peace FM while in a trotro, enjoying music on Joy FM, to following live football commentary on Adom FM. Understanding how a simple radio set captures these invisible waves from the air and turns them into sound is a key skill in applied electronics. We will explore the journey of a radio signal from the antenna to the speaker by breaking down AM and FM receivers into their functional blocks.
Before we can understand the receiver, we must quickly recap the signals they are designed to receive: AM and FM waves. Carrier Wave: A high-frequency wave that is used to "carry" the lower-frequency audio signal (our voice or music). Modulation: The process of changing a property of the carrier wave (like its amplitude or frequency) in accordance with the audio signal. Amplitude Modulation (AM): The amplitude (height or strength) of the carrier wave is varied according to the audio signal. The frequency remains constant. Frequency Modulation (FM): The frequency of the carrier wave is varied according to the audio signal. The amplitude remains constant.
Most modern radio receivers use a design called the superheterodyne principle. This is a clever technique that converts any selected radio frequency (RF) into a fixed, lower frequency called the Intermediate Frequency (IF). Amplifying and filtering a fixed frequency (the IF) is much easier and more stable than trying to handle all the different frequencies coming from various radio stations. A. The Superheterodyne AM Receiver
The AM receiver is designed to capture AM signals, process them, and reproduce the original audio. Here is the block diagram and the function of each stage.
Block Diagram of a Superheterodyne AM Receiver: