Lesson Notes By Weeks and Term v4 - SHS 3
ELECTRONIC COMPONENTS AND CIRCUITS
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ELECTRONIC COMPONENTS AND CIRCUITS
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Subject: Applied Technology
Class: SHS 3
Term: 2nd Term
Week: 20
Grade code: 2.5.2.LI.11
Strand code: 4
Sub-strand code: 2
Content standard code: 2.5.2.CS.1
Indicator code: 2.5.2.LI.11
Theme: ELECTRICAL AND ELECTRONIC TECHNOLOGY
Subtheme: ELECTRONIC COMPONENTS AND CIRCUITS
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Welcome, students! Today, we are diving into the exciting world of radio communication. Every time you tune into Joy FM for the news, Peace FM for ‘Kokrokoo’, or your local community radio station, you are experiencing the end result of a process that begins at a transmitter. A transmitter is the device that takes a voice or music, converts it into an electronic signal, and sends it flying through the air as invisible radio waves. Understanding how these transmitters work is fundamental to appreciating modern communication technology, from broadcasting to walkie-talkies used by security personnel.
Before we look at the transmitters, we must understand the core principle: Modulation.
What is Modulation? Imagine you want to send a letter (your message) from Accra to Tamale. You can't just throw the piece of paper into the air and hope it gets there. You need to put it on a vehicle, like a bus or an aeroplane (a carrier), that is designed to travel long distances.
In electronics, our message (e.g., voice or music) is a low-frequency signal called the modulating signal or baseband signal. This signal is weak and cannot travel far on its own. To send it over a long distance, we superimpose it onto a high-frequency signal called the carrier wave. This process of superimposing a low-frequency message signal onto a high-frequency carrier wave is called Modulation. The transmitter does this modulation.
There are two main types of analogue modulation we will study: Amplitude Modulation (AM): The amplitude (strength or height) of the high-frequency carrier wave is changed in proportion to the instantaneous amplitude of the modulating signal. The frequency of the carrier remains constant. *Analogy:* Imagine the bus to Tamale (carrier) is blinking its lights. In AM, the *brightness* of the lights changes based on the information in your letter. The speed of the bus remains the same. Frequency Modulation (FM): The frequency (number of cycles per second) of the high-frequency carrier wave is changed in proportion to the instantaneous amplitude of the modulating signal. The amplitude of the carrier remains constant. *Analogy:* In FM, the brightness of the bus lights stays constant, but the *speed* of the bus changes based on the information in your letter.