Applied Physics

• AM and FM radio play vital roles in everyday life by providing auditory communication, entertainment, companionship, and real-time information
• Radio stations motivate learning and promote values and virtues
• Radio is used in the Distance Learning Modality of the Department of Education to help educate learners
• Ways of transmitting radio signals are Amplitude Modulation (AM) and Frequency Modulation (FM)
• AM works by varying the signal or carrier amplitude while maintaining a constant frequency
• FM works by varying the wave frequency while keeping the amplitude constant
• A radio show starts with audio production, captured by a microphone and transmitted as electrical signals
• Modulation combines the audio signal with the carrier wave for broadcasting
• The signal is broadcast as electromagnetic waves from the radio station's antenna
• Radio receivers pick up waves, amplify them, and convert them back into sound through the speaker
• Radio stations broadcast at specific frequencies, and the receiver must be tuned to the precise frequency to receive the signal
• FM stations sound better than AM stations due to higher frequency range and bandwidth
• AM radio varies the amplitude of the broadcast signal, affecting signal strength, while FM remains at constant amplitude
• FM stations have a larger bandwidth than AM stations, allowing them to transmit more information and produce better sound quality, especially for music
• Zero-crossing is the point where there is no voltage present in alternating current
• Zero-crossing is important for systems sending digital data over AC circuits and in speech processing to estimate the fundamental frequency of speech
• AM stands for Amplitude Modulation
• AM method of audio transmission was first successfully carried out in the mid-1870s
• In AM, a radio wave is modulated in amplitude by the signal to be transmitted, while the frequency and phase remain the same
• AM has poorer sound quality than FM, but it is cheaper and can transmit over long distances
• AM radio ranges from 535 to 1705 KHz (or up to 1200 bits per second)
• Bandwidth requirement for AM is twice the highest modulating frequency, resulting in a bandwidth of 30kHz
• AM is more susceptible to noise because noise affects amplitude, where information is "stored" in an AM signal
• FM stands for Frequency Modulation
• FM radio was developed in the United States in the 1930s, mainly by Edwin Armstrong
• In FM, a radio wave is modulated in frequency by the signal to be transmitted, while the amplitude and phase remain the same
• FM is less prone to interference than AM, but FM signals are impacted by physical barriers
• FM has better sound quality due to higher bandwidth
• FM radio ranges from 88 to 108 MHz (or 1200 to 2400 bits per second)
• Bandwidth requirement for FM is twice the sum of the modulating signal frequency and the frequency deviation
• FM is less susceptible to noise because the information in an FM signal is transmitted through varying the frequency, not the amplitude
• Complexity of AM and FM systems
• AM systems have simple transmitters and receivers, but synchronization is needed
• FM systems have more complex transmitters and receivers as the variation of modulating signal needs to be converted and detected from the corresponding variation in frequencies
• Zero crossings in modulating the signal are equidistant for AM and not equidistant for FM
• AM method of audio transmission was first successfully carried out

  mid-1870s
• AM


  Stands for Amplitude Modulation
• Bandwidth Requirements


  • AM: Twice the highest modulating frequency, bandwidth of an amplitude-modulated signal is 30kHz
  • FM: Twice the sum of the modulating signal frequency and the frequency deviation, bandwidth required is 180kHz
• Sound quality varies based on location and physical barriers
• AM has poorer sound quality than FM, but is cheaper and can transmit over long distances. It has a lower bandwidth, allowing more stations in any frequency range