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ECE :: Communication Systems

  1. Two sinusoidal signals of same amplitude and frequencies 10 kHz and 10.1 kHz are added together. The combined signal is given to an ideal frequency detector. The output of the detector is

  2. A.
    0.1 kHz sinusoidal
    B.
    10.1 kHz sinusoidal
    C.
    a linear function
    D.
    a constant

  3. In Vidicon camera tube, the resistance of photoconductive material on the target plate

  4. A.
    is constant
    B.
    is more in darkness and less in brightness
    C.
    is more in brightness but less in darkness and brightness
    D.
    may be more or less in darkness and brightness

  5. In a satellite transponder the power amplifier feeds power P to the transmitting antenna of gain G. If distance of earth is d, the power flux density is

  6. A.
    PG/d
    B.
    PG/4pd2
    C.
    P/G(4pd2)
    D.

  7. The percentage saving in power of 100% modulated suppressed carrier AM signal is

  8. A.
    100
    B.
    75
    C.
    66.6
    D.
    50

  9. Which of the following are useful in comparing the noise performance of receivers?

    1. Input noise voltage
    2. Noise figure
    3. Noise resistance
    4. Noise temperature
    Select answer as per the following codes:

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

  11. Compact discs use

  12. A.
    magnetic recording and retrieval
    B.
    optical recording and retrieval
    C.
    optical recording but magnetic retrieval
    D.
    magnetic recording but optical retrieval

  13. A carrier is phase modulated (PM) with frequency deviation of 10 kHz by a single tone frequency of 1 kHz. If the single tone frequency is increased to 2 kHz, assuming that phase deviation remains unchanged, the bandwidth of the PM signal is

  14. A.
    21 kHz
    B.
    22 kHz
    C.
    42 kHz
    D.
    44 kHz

  15. In a communication receiver, a squelch circuit is normally inserted

  16. A.
    before detector
    B.
    after detector
    C.
    before mixer
    D.
    after power amplifier

  17. In PCM, the information lies

  18. A.
    in one or two properties of the pulse
    B.
    in absence of pulse
    C.
    in presence of pulse
    D.
    in presence or absence of pulse

  19. A carrier is simultaneously modulated by two sine waves having modulation indices of 0.4 and 0.3. The total modulation index will be

  20. A.
    0.1
    B.
    0.7
    C.
    0.5
    D.
    0.35