ELECTRONICS Q3

• Radio is the first wireless mode of communication that sends messages by radio waves instead of wires
• German scientist Heinrich Hertz proved the existence of radio waves
• In 1895, Gugliemo Marconi invented the wireless telegraph using radio waves to transmit Morse code
• Marconi shared the Nobel Prize for physics in 1906 with Ferdinand Braun for their contributions to wireless telegraphy
• Radio works by changing sounds or signals into radio waves, which travel through air, space, and solid objects, and the radio receiver changes them back into sounds, words, and music
• A radio broadcast is a one-way transmission originating from a radio station
• In the early 1920s, radio played an important role in people's lives with over 500 stations broadcasting news, music, sports, drama, and variety shows
• By the 1930s, most households in the U.S. and Europe had at least one radio
• The "Golden Age of Radio" began where families gathered around radios to listen to shows like "The Lone Ranger", "The Shadow", "I Love a Mystery", and children's shows like "Let's Pretend" and "Hop Harrigan"
• Reginald Fessenden sent the first long-distance transmission of human voice and music in 1906 from Brant Rock, Massachusetts
• Guglielmo Marconi, an Italian physicist and inventor, received the Nobel Prize for Physics in 1909 for his work on wireless telegraphy
• Marconi later worked on the development of shortwave wireless communication, which is the basis of modern long-distance radio
• Ways of transmitting radio signals: Amplitude Modulation (AM) and Frequency Modulation (FM)
• Both AM and FM transmit information in the form of electromagnetic waves
• Amplitude Modulation varies the signal or carrier amplitude while maintaining a constant frequency
• Frequency Modulation encodes information by varying the wave frequency and keeping the amplitude constant
• Radio show production process:

  • Audio is produced by people speaking
  • Sounds are captured and turned into an electrical signal by a microphone
  • The signal is transmitted immediately or stored for later use
• Modulation:

  • Modulation combines the electrical signal with a carrier wave to broadcast
  • Modulation refers to converting data by adding information to a carrier signal into radio waves
• Modulation methods:

  1. Changing the amplitude of the carrier wave (Amplitude Modulation)

  • Signal is broadcast as electromagnetic waves from the radio station's antenna
  • Receiver picks up waves, amplifies, and converts them back into sound

  2. Changing the frequency of the carrier wave (Frequency Modulation)
• Differences between AM and FM:

  • AM varies the amplitude of the broadcast signal, affecting signal strength
  • FM remains at a constant amplitude, ensuring signal strength does not change
  • FM uses a higher frequency range and bandwidth than AM
• Bandwidth and broadcasting:

  • AM radio operates from 535 kHz to 1705 kHz with 10 kHz bandwidth per station
  • FM radio operates between 88 MHz and 108 MHz with 200 kHz increments
  • FM stations have 15 times more bandwidth than AM stations, allowing for better sound quality
• Zero-crossing in alternating current:

  • Zero-crossing is the point where there is no voltage present in AC
  • It is important for systems sending digital data over AC circuits
  • Zero-crossing is used in speech processing to estimate fundamental frequency
• AM (Amplitude Modulation) is modulated in amplitude by the signal that is to be transmitted
• AM has a poorer sound quality than FM
• AM is cheaper and can transmit over long distances
• AM has a lower bandwidth, allowing for more stations available in any frequency range
• FM (Frequency Modulation) is modulated in frequency by the signal that is to be transmitted
• FM is less prone to interference than AM
• FM has better sound quality due to higher bandwidth
• AM radio ranges from 535 to 1705 KHz (or) up to 1200 hits per second
• FM radio ranges from 88 to 108 MHz or 1010 to 1200 to 2400 bit per second
• Bandwidth requirements:

  • For AM: Twice the highest modulating frequency, with a bandwidth of 30kHz for a modulating signal bandwidth of 15kHz
  • For FM: Twice the sum of the modulating signal frequency and the frequency deviation, with a bandwidth of 180kHz for a frequency deviation of 75kHz and a modulating signal frequency of 15kHz
• Complexity:

  • AM is more susceptible to noise because noise affects amplitude, where information is stored in an AM signal
  • FM is less susceptible to noise because the information in an FM signal is transmitted through varying the frequency, not the amplitude