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ECE :: Communication Systems

  1. In grid bias modulation system the power required for modulating amplifier

  2. A.
    is negligibly low since grid is negative
    B.
    is large as compared to that for plate modulation
    C.
    is almost the same as compared with plate modulation
    D.
    is small as compared to that for plate modulation

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  3. In spread spectrum technique

  4. A.
    a modulated signal is modulated again
    B.
    a modulated signal is modulated twice again
    C.
    the power of a modulated signal is increased
    D.
    the noise component of a modulated signal is decreased

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  5. QAM stands for

  6. A.
    Quasi-Amplitude Modulation
    B.
    Quadrature Angle Modulation
    C.
    Quadrature Amplitude Modulation
    D.
    None of the above

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  7. The bandwidth required for amplitude modulation is

  8. A.
    half the frequency of modulating signal
    B.
    equal to the frequency of modulating signal
    C.
    twice the frequency of modulating signal
    D.
    four times the frequency of modulating signal

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  9. The smallest change in sound intensity that can be detected by human ear is __________ dB.

  10. A.
    1
    B.
    3
    C.
    10
    D.
    20

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  11. Low frequency boost can be easily compensated by

  12. A.
    attenuating the frequencies from 0 to 1.25 MHz
    B.
    using an appropriate de-emphasis circuit in the receiver
    C.
    using an appropriate pre-emphasis circuit in the transmitter
    D.
    none

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  13. An MTI compares a set of received echos with those received during the previous sweep.

  14. A.
    True
    B.
    False

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  15. If e = 10 sin(108 t + 3 sin 104 t) then the deviation is

  16. A.
    4.77 kHz
    B.
    47.7 kHz
    C.
    477 kHz
    D.
    4770 kHz

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  17. When a complex signals is used to frequency modulate a carrier, the resulting sideband distribution is

  18. A.
    symmetrical about the carrier
    B.
    not necessarily symmetrical about the carrier
    C.
    decided by the predominant sidebands
    D.
    none of the above

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