Amplitude and Frequency Modulation

• Amplitude and Frequency Modulation are the focus of Quarter 3 - Module 1.

Activity 1: Know my Station

• Find the frequencies and names of local and Philippine radio stations.
• Use a ball pen, paper, and an AM/FM radio to record your findings.
• Turn on the radio and locate five AM and five FM radio stations.
• Record these in a table with station names and their corresponding amplitudes/frequencies.
• Answer guide questions about AM and FM radio, their differences, ease of locating stations, frequencies of nearby stations, names of nearby stations, and challenges faced during the activity.
• Examples of stations include: DZRH Nationwide with a frequency of 666 (AM) and Love Radio with a frequency of 90.7 (FM).

Learning Objectives

• Define Amplitude Modulation (AM) and Frequency Modulation (FM).
• Key differences between AM and FM in terms of signal characteristics and applications will be identified.
• Real-world applications of AM and FM in communication systems are to be analyzed.

What is Modulation?

• Modulation is the process of varying a carrier wave to transmit information.
• Modulation is important because it allows information, such as audio, video, and data, to be sent over long distances.

Amplitude Modulation (AM)

• Amplitude modulation (AM) is a technique where a carrier wave's amplitude varies based on the information signal.
• AM radio broadcasts use lower carrier frequencies, allowing them to travel long distances and bounce off the ionosphere.
• AM signals can travel greater distances than FM signals.
• With AM, the carrier wave's amplitude changes according to the signal's information.
• AM systems are simplistic and cost-effective but are prone to noise and interference.
• AM has lower sound quality compared to FM
• Amplitude modulation works by changing the amplitude or height of the carrier wave.

Frequency Modulation (FM)

• Frequency modulation (FM) modifies the carrier wave's frequency based on the signal carrying information.
• FM radio signals have larger bandwidths than AM signals, offering better sound quality and enabling the transmission of stereo signals.
• With FM, the frequency of the carrier wave changes based on the signal's information.
• FM provides higher sound quality and is less prone to noise and interference.
• FM requires more bandwidth
• Frequency modulation changes the frequency or speed of the carrier wave.

Comparison of AM and FM

• AM audio transmission started in the mid-1870s.
• FM radio developed in the United States, mainly by Edwin Armstrong, in the 1930s.
• AM has poorer sound quality but is cheaper and transmits over long distances.
• AM has a lower bandwidth, allowing more stations in any frequency range.
• FM is less prone to interference than AM but is affected by physical barriers.
• FM provides better sound quality because it has a higher bandwidth.
• AM radio ranges from 535 to 1705 KHz or up to 1200 bits per second.
• FM radio ranges from 88 to 108 MHz or 1200 to 2400 bits per second.
• Bandwidth is the amount of space a signal needs to send information over a specific range of frequencies.
• AM requires narrow bandwidth, while FM requires wider bandwidth.
• FM carries higher-quality sound and encodes more detailed information because it uses a wider range.
• AM waves have even spacing and are equidistant.
• FM waves have uneven spacing and are not equidistant.
• AM is more susceptible to noise since noise affects the amplitude where information is stored.
• FM is less susceptible to noise because information is transmitted through frequency variation, not amplitude.
• AM applications include news broadcasts, talk radio, and long-distance communication.
• FM applications include music broadcasting, high-fidelity audio systems, and local radio stations.

Summary of AM and FM

• AM and FM are two common modulation techniques.
• AM is simpler, has a wider range, has lower quality, and is prone to more interference.
• FM offers higher quality and less interference but has a limited range.

Venn Diagram Activity: AM vs FM

• Shared characteristics include: Use waves to send signals, use transmitters and receivers, require modulation to carry information, and use antennas to send and get signals.
• FM specific: Frequency changes to send information, better sound quality, and is good for music.
• AM specific: Transmits over longer distances, uses amplitude changes to send information, is affected by static and noise, uses less space, and is used for news or talk shows.

Activity 3: Short Essay

• Write a short essay about the better choice to design and create a radio station, AM or FM.
• The essay will be graded based on content, relevance, and organization.