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ECE :: Communication Systems

  1. If D is mouth diameter of a paraboloid reflector, its directivity is proportional to

  2. A.
    D
    B.
    D2
    C.
    D
    D.
    D3

  3. A noiseless 3 kHz channel can't transmit binary bit at the rate

  4. A.
    12000 bps
    B.
    1000 bps
    C.
    6000 bps
    D.
    3000 bps

  5. In an AM wave the carrier and one of the side bands is suppressed. If m = 1, the percentage saving in power is

  6. A.
    25%
    B.
    50%
    C.
    66.6%
    D.
    83.3%

  7. Assertion (A): An electronic tuner uses varactor diode

    Reason (R): The capacitance of a varactor diode depends on the magnitude of reverse bias.

  8. A.
    Both A and R are correct and R is correct explanation of A
    B.
    Both A and R are correct but R is not correct explanation of A
    C.
    A is correct but R is wrong
    D.
    A is wrong but R is correct

  9. A superheterodyne receiver is to operate in the frequency range 550 kHz - 1650 kHz, with the intermediate frequency of 450 kHz. Let denote the required capacitance ratio of the local oscillator and I denote the image frequency (in kHz) of the incoming signal. If the receiver is tuned to 700 kHz, then

  10. A.
    R = 4.41 J =1600
    B.
    R = 2.10 J =1150
    C.
    R = 3.0 J =1600
    D.
    R = 9.0 J =1150

  11. In a tape recorder the output from RF oscillator is given to

  12. A.
    only erase head coil
    B.
    only record head coil
    C.
    coils of both erase head and record head
    D.
    none of the above

  13. A + 1.9 lens has a focal length of 25 mm. The diameter of lens is about

  14. A.
    13 mm
    B.
    1.3 mm
    C.
    130 mm
    D.
    none of the above

  15. Which of the following terms are applicable to troposcatter propagation?

  16. A.
    Faradays rotation
    B.
    SIOs
    C.
    Fading
    D.
    Atmospheric storms

  17. If the amplitude of the voltage is kept constant, but its frequency is raised to 6 kHz, the new deviation will be for the modulation index is, if fm = 500 Hz, Δf = 2.25

  18. A.
    6 kHz
    B.
    12 kHz
    C.
    27 kHz
    D.
    54 kHz

  19. In TV scanning sequence of lines is

  20. A.
    left to right
    B.
    right to left
    C.
    left to right for odd fields and right to left for even field
    D.
    left to right for even fields and right to left for odd field