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  • Question
  • Which of the following has the highest input impedance?


  • Options
  • A. CE
  • B. CB
  • C. CC
  • D. Push pull

  • Correct Answer
  • CC 

    Explanation
    CC connection has very high input impedance and low output impedance.

    Communication Systems problems


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    • 1. Frequency shift keying is used mostly in

    • Options
    • A. telegraphy
    • B. telephony
    • C. satellite communication
    • D. radio transmission
    • Discuss
    • 2. In colour TV receiver, varactor diode is used for

    • Options
    • A. detection
    • B. rectification
    • C. tuning
    • D. both (a) and (b)
    • Discuss
    • 3. Which of the following cannot be the Fourier series expansion of a periodic signal?

    • Options
    • A. x(t) = 2 cos t + 3 cos 3t
    • B. x(t) = 2 cos pt + 7 cos t
    • C. x(t) = cos t + 0.5
    • D. x(t) = 2 cos 1.5pt + sin 3.5 pt
    • Discuss
    • 4. If C is capacity of noisy channel, (bits/s), ?f is bandwidth Hz and S/N is signal to noise ratio, then

    • Options
    • A.
    • B.
    • C.
    • D.
    • Discuss
    • 5. A 1000 kHz carrier is simultaneously modulated with 300 Hz, 800 Hz and 2 kHz audio sine waves. Which of the following frequency is least likely to be present in the output?

    • Options
    • A. 1002 kHz
    • B. 1000 kHz
    • C. 999.2 kHz
    • D. 998.0 kHz
    • Discuss
    • 6. Degaussing in a picture tube means

    • Options
    • A. Adding magnetism in mask and mounting frame
    • B. Removing residual magnetism in mask, shield etc...
    • C. Increasing resistance of coils to decrease time constant
    • D. Decreasing resistance of coils to increase time constant.
    • Discuss
    • 7. Space wave may be a direct wave or wave reflected from earth.

    • Options
    • A. True
    • B. False
    • Discuss
    • 8. If the bandwidth is increased by 2, the ?FM ?AM (where ? is the ratio of SNR of output to SNR at input, FM is frequency modulation and AM is amplitude modulation) is increased by a factor of

    • Options
    • A. 2
    • B. 3
    • C. 4
    • D. 6
    • Discuss
    • 9. When the channel is noisy, producing a conditional probability of error p = 0.5; the channel capacity and entropy function would be, respectively,

    • Options
    • A. 1 and 1
    • B. 1 and 0.5
    • C. 0.5 and 1
    • D. 0 and 1
    • Discuss
    • 10. c(t) and m(t) are used to generate an FM signal. If the peak frequency deviation of the generated FM signal is three times the transmission bandwidth of the AM signal, then the coefficient of the term cos [2p(1008 x 103t)] in the FM signal (in terms of the Bessel Coefficients) is

    • Options
    • A. 5 J4(3)
    • B. J8(3)
    • C. J8(4)
    • D. 5 J4(6)
    • Discuss


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