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ECE :: Communication Systems

  1. In high power radars, which of the following are used for switching?

  2. A.
    Power diode
    B.
    Power BJT
    C.
    Power MOSFET
    D.
    Thyristor

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  3. A remote control for TV uses

  4. A.
    LED in receiver and photodiode in transmitter
    B.
    LED in transmitter and photodiode in receiver
    C.
    LED in both transmitter and receiver
    D.
    Photodiode in both transmitter and receiver

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  5. In the FM wave described by equation v = 15 sin (4 x 108 t + 3 sin 1100 t), the carrier frequency and signal frequency respectively are

  6. A.
    63.66 MHz and 175 Hz
    B.
    4 x 108 Hz and 1100 Hz
    C.
    175 Hz and 63.66 MHz
    D.
    1100 Hz and 4 x 108 Hz

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  7. A sequence x(n) with the z transform X(z) = z4 + z2 - 2z + 2 - 3z - 4 is applied as an input to a linear, time invariant system with the impulse response h(n) = 2δ(n - 3) where

    The output at n = 4 is

  8. A.
    - 6
    B.
    zero
    C.
    2
    D.
    - 4

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  9. Which of the following amplifiers is used for impedance matching?

  10. A.
    CE
    B.
    CC
    C.
    CB
    D.
    Push pull

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  11. Which of the following amplifiers has highest output impedance?

  12. A.
    CE
    B.
    CB
    C.
    CC
    D.
    Push pull

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  13. In a superheterodyne receiver, having no RF amplifier, the IF is 455 kHz. The image frequency at 1000 kHz is

  14. A.
    1455 kHz
    B.
    545 kHz
    C.
    1910 kHz
    D.
    90 kHz

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  15. Audio tapes have two tracks each 2.5 mm wide.

  16. A.
    True
    B.
    False

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  17. Which of the following amplifiers has a voltage gain of less than 1?

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

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