Telecommunications: Radio and Television

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Author:
crobertsonx
ID:
86661
Filename:
Telecommunications: Radio and Television
Updated:
2011-05-18 21:08:19
Tags:
Telecommunications Radio Television physics
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Description:
Telecommunications: Section 3- Radio and Television
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  1. what are the main parts of a radio receiver?
    aerial -> tuner -> decoder -> amplifier ^ power supply ^ -> loudspeaker
  2. what does the aeriel in a radio receiver do?
    picks up radio waves of many different frequencies and converts them into electrical signals
  3. what does the tuner in a radio receiver do?
    selects one particular frequency from the many received by the aerial
  4. what does the decoder in a radio receiver do?
    extracts the audio signal from the transmitted radio signal
  5. what does the amplifier in a radio receiver do?
    increases the strength of the electrical signal
  6. what does the loudspeaker in a radio receiver do?
    converts the electrical signal into sound
  7. what does the power supply in a radio receiver do?
    supplies extra energy for the amplifier
  8. how are radio signals produced?
    • changing the amplitude of a high frequency carrier wave according to the audio signal that is to be carried.
    • this known as amplitude modulation (AM)
  9. what happens in FM?
    • in frequency modulation it is the frequency of the carrier wave that is changed according to the audio signal
    • this produces a higher quality signal since interference has little effect on the frequency of the transmitted radio wave
  10. what are the main parts of a television receiver?
    • aerial -> tuner
    • -> audio decoder -> audio amplifier -> loudspeaker
    • |
    • -> vision decoder -> vision amplifier -> picture tube
  11. what does the aerial of a television receiver do?
    picks up television waves of many different frequencies and converts them into electrical signals
  12. what does the tuner of a television receiver do?
    selects one particular frequency from the many received by the aerial
  13. what does the audio decoder of a television receiver do?
    selects extracts the audio signal from the transmitted television signal
  14. what does the audio amplifier of a television receiver do?
    increases the strength of the electrical audio signal
  15. what does the loudspeaker of a television receiver do?
    converts the electrical signal into sound
  16. what does the vision decoder of a television receiver do?
    extracts the vision signal from the transmitted television signal
  17. what does the vision amplifier of a television receiver do?
    increases the strength of the electrical vision signal
  18. what does the picture tube of a television receiver do?
    converts the electrical signal into light
  19. why is there a power supply in a television receiver?
    to supply extra energy to the amplifiers
  20. what does the picture consist of? what does it do?
    • consists of an electron gun situated inside an evacuted glass tube, which is painted with a special phosphor coating
    • the electron gun fires a beam of electrons at the phosphor paint on the screen where the kinetic energy of the electrons is turned into a spot of light
  21. how is a picture built up on the TV screen?
    • by moving the electron beam across the screen in a series of lines
    • as the beam moves across the screen the brightness of the spot is altered by changing the number of electrons hitting each part of the screen
    • a new picture is produced 25 times each seconds and because our eyes retain the image on the retina of the eye, each picture merges into the next
    • since each picture is only slightly different from the previous one the picture appears to move
  22. what is the difference in the way television signals are transmitted compared with radio signals?
    • TV signals
    • the carrier wave is modulated to carry two synchronised signals, each signal is then extracted by a seperate decoder
  23. describe a colour television.
    • A colour television has three different coloured phosphor dots at each point on the screen.
    • One electron gun fires at each colour and by altering the number of electrons fired at each dot they are lit up with varying brightness.
    • This allows all the colours to be produced by colour mixing.
  24. what colours are used in colour TV?
    • red
    • green
    • blue

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