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ECE :: Communication Systems

  1. Which of the following microphones has bidirectional feature?

  2. A.
    Moving coil
    B.
    Ribbon
    C.
    Condenser
    D.
    Carbon

  3. In TV transmitter some possible advantages of IF modulation are

    1. The modulator section and visual exciter can be solid state devices
    2. VSB filter can be introduced at low power level
    3. The subsequent stages following VSB filter can be tuned permanently for wideband linear operation
    4. It is economical
    which of the above are true?

  4. A.
    1 and 2
    B.
    1, 2 and 3
    C.
    2, 3 and 4
    D.
    1, 2, 3 and 4

  5. A source is radiating power equally in all directions. If source power is P, the power density at distance d is


  6. As compared to AM, FM requires

  7. A.
    narrow channel
    B.
    same channel
    C.
    2 to 3 times as large channel
    D.
    7 to 15 times as large channel

  8. Capture effect occurs in

  9. A.
    AM
    B.
    FM
    C.
    PCM
    D.
    QAM

  10. Narrowband FM signal can be considered to be equal to

  11. A.
    PM
    B.
    AM
    C.
    SSB
    D.
    DSB

  12. The spectral component of noise associated with kth frequency is given, in the limit as Δf → 0 by nk(t) written as nk(t) = Ck cos (2pk Δft + θk)
    Consider the following statements as regards Ck and θk

    1. Ck and θk are independent of one another
    2. Ck and θk are independent of the amplitude of a spectral component at a different frequency
    3. Ct and θk are independent of the phase of a spectral component at a different frequency
    Which of the above statements are correct?

  13. A.
    1, 2 only
    B.
    1, 3 only
    C.
    1, 2, 3
    D.
    2, 3 only

  14. The power density spectrum of noise voltage at the input of a network is Sni and that at the output of the network is Sno. If transfer function of network is H(ω), the corresponding noise figure is


  15. A narrowband amplifier is one that has a passband

  16. A.
    limited to 2000 Hz only
    B.
    limited to audio frequency range only
    C.
    near cut off region of active device
    D.
    approximately 10% of its central frequency

  17. In a modulator it is found that the amplitude spectrum consists a component at fc, the carrier frequency and one component each at fc - fs and fc + fs where fs is the modulating signal frequency. Then the modulator used is

  18. A.
    AM
    B.
    AM or MBFM with modulation index 0.5
    C.
    FM
    D.
    PAM