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ECE :: Communication Systems

  1. In a single sideband suppressed carrier AM system, the modulation index is changed from 0 to 1, the power content of the signal

  2. A.
    will be quarter
    B.
    will be doubled
    C.
    will increase by 50 percent
    D.
    will increase by 25 percent

  3. The primary colours are

  4. A.
    blue and green
    B.
    blue and red
    C.
    red and green
    D.
    blue, red and green

  5. The most commonly used system of modulating for telegraphy is

  6. A.
    single tone modulation
    B.
    on-off keying
    C.
    frequency shift keying
    D.
    pulse code modulation

  7. Which of the following antennas is not wide band?

  8. A.
    Marconi
    B.
    Helical
    C.
    Folded dipole
    D.
    Discone

  9. While AM has __________ frequencies, FM has __________ number of sidebands.

  10. A.
    2, 3
    B.
    3, 3
    C.
    3, 5
    D.
    3, infinite

  11. In VHS format diameter of head drum is about

  12. A.
    1 m
    B.
    20 cm
    C.
    6 cm
    D.
    1 cm

  13. The correct sequence of subsystem in an FM receiver is

  14. A.
    mixer, RF amplifier, limiter, IF amplifier, discriminator, audio amplifier
    B.
    RF amplifier, mixer, IF amplifier, limiter, discriminator, audio amplifier
    C.
    RF amplifier, mixer, limiter, discriminator, IF amplifier, audio amplifier
    D.
    mixer, IF amplifier, limiter, audio amplifier, discriminator

  15. A wave is frequency modulated with an index of 0.1 and its frequency is multiplied by 8 times, the modulation index is

  16. A.
    not changed
    B.
    decreased 8 times
    C.
    increased 4 times
    D.
    increased 8 times

  17. Short circuited stubs are preferred to O.C stubs because

  18. A.
    O.C stubs are incapable of giving full range of reactances
    B.
    O.C stubs are liable to radiate
    C.
    O.C stubs are difficult to make and connect
    D.
    none of the above

  19. When ωm is the modulation frequency in frequency modulation, the modulation index is proportional to

  20. A.
    ωm
    B.
    ω2m
    C.
    1/ωm
    D.
    1/ω2m