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ECE :: Communication Systems

  1. Reception through space wave is limited to line of sight distance.

  2. A.
    True
    B.
    False

  3. A video transmission system transmits 625 picture frames per second. Each frame consist of a 400 x 400 pixel grid with 64 intensity levels per pixel. The data rate of the system is

  4. A.
    16 Mbps
    B.
    100 Mbps
    C.
    600 Mbps
    D.
    6.4 Gbps

  5. Which of the following is a false statement about Armstrong modulation system?

  6. A.
    The system is basically phase, not frequency, modulation
    B.
    AFC is not needed, as a crystal oscillator is used
    C.
    Equalization is unnecessary
    D.
    Frequency multiplication must be used

  7. Which one is digital modulation technique?

  8. A.
    AM
    B.
    PAM
    C.
    PCM
    D.
    None

  9. Since noise phase modulated FM wave, as the noise sideband frequency approaches the carrier frequency, the noise amplitude

  10. A.
    is equalized
    B.
    is increased
    C.
    is decreased
    D.
    remains constant

  11. Consider the following statements as regards SAW filter

    1. The centre frequency is determined by the pitch of IDT comb shaped electrodes
    2. The response can be modified shaping the overlap of comb electrodes
    3. The response is maximum when acoustic wave has its wavelength equal to pitch
    4. When a number of identical electrodes are arranged at the same pitch, the frequency characteristics of the filter is expressed by (sin x)/x
    Which of the above statements are correct?

  12. A.
    1, 2, 3, 4
    B.
    1, 2, 3 only
    C.
    1, 2, 4 only
    D.
    2, 3, 4 only

  13. In telephone, the dial tone has a frequency of

  14. A.
    5 Hz
    B.
    15 Hz
    C.
    33 Hz
    D.
    233 Hz

  15. Companding is used

  16. A.
    to overcome quantising noise in PCM
    B.
    in PWM receivers to reduce impulse noise
    C.
    to protect small signals in PCM from quantising noise
    D.
    none of the above

  17. For a good public address system the sound intensity at the farthest point should be at least

  18. A.
    20 dB over threshold of hearing
    B.
    40 dB over threshold of hearing
    C.
    80 dB over threshold of hearing
    D.
    120 dB over threshold of hearing

  19. An ungrounded antenna near the ground

  20. A.
    is horizontally polarized
    B.
    acts as an antenna array
    C.
    acts as a single antenna of twice the height
    D.
    is not likely to need an earth mat