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ECE :: Communication Systems

  1. A 1000 kHz carrier is simultaneously modulated by 300 Hz and 2 kHz audio sine wave. Which of the following frequencies will not be present in the output?

  2. A.
    998 kHz
    B.
    999.7 kHz
    C.
    1000.3 kHz
    D.
    700 kHz

  3. SWR for a transmission line is infinity when the load is

    1. Short circuit
    2. Complex impedance
    3. Open circuit
    4. Pure reactance
    Of the above statements:

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

  5. The discone antenna is

  6. A.
    used in UHF range
    B.
    circularly polarized
    C.
    used in radar
    D.
    used as a direction finding antenna

  7. The direction of pick up in a CD is

  8. A.
    linear from centre towards edge
    B.
    linear from edge to centre
    C.
    nonlinear from centre to edge
    D.
    nonlinear from edge to center

  9. A (75 - j 50) Ω load is connected to a coaxial line of Z0 = 75 Ω at 10 GHz. The best method of matching consists of using

  10. A.
    a capacitance at some specific distance from load
    B.
    a short circuited stub at some specific distance from load
    C.
    an inductance at load
    D.
    a short circuited stub at load

  11. In PCM the amplitude levels are transmitted in a 7 unit code. Sampling frequency is 10 kHz. The bandwidth should be

  12. A.
    5 kHz
    B.
    35 kHz
    C.
    70 kHz
    D.
    5 MHz

  13. In colour television V and U signals are

  14. A.
    same as I and Q signal
    B.
    same as R - Y and B - Y
    C.
    modified I and Q signal
    D.
    modified R - Y and B - Y

  15. Which of the following has highest power gain?

  16. A.
    CE
    B.
    CC
    C.
    CB
    D.
    CB or CC

  17. Two messages m1, and m2 have a probability of 0.5 each. The entropy is

  18. A.
    0.25
    B.
    0.5
    C.
    0.75
    D.
    1

  19. A TV receiver is 40 cm wide and 30 cm high. The EHT supply required is about

  20. A.
    2kV
    B.
    20 kV
    C.
    53 kV
    D.
    10 W