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ECE :: Communication Systems

  1. The Shannon-Hartley law

  2. A.
    refers to noise
    B.
    defines bandwidth
    C.
    describes signalling rate
    D.
    refers to distortion

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  3. In radar PRF depends on maximum range.

  4. A.
    True
    B.
    False

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  5. A frequency doubler has an FM signal input at 13 MHz with a deviation of 5 kHz. The output frequency of the carrier will be

  6. A.
    26 kHz
    B.
    260 kHz
    C.
    26 MHz
    D.
    260 MHz

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  7. If fh(t) is Hilbert transform of f(t), then Hilbert transform of fh(t) is

  8. A.
    -f(t)
    B.
    +f(t)
    C.
    f2(t)
    D.
    f(t)

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  9. Maximum undistorted power output of a transmitter is obtained when its modulation is __________ percent.

  10. A.
    more than 100
    B.
    100
    C.
    less than 100
    D.
    50

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  11. Which one of the following is not necessarily an advantage of the phase cancellation method of obtaining SSB over the filter method?

  12. A.
    It is possible to generate SSB at any frequency
    B.
    SSB with lower audio frequencies present can be generated
    C.
    Switching from one sideband to other is simpler
    D.
    There are more balanced modulators; therefore the carrier is suppressed better

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  13. Pulse modulation is used in

  14. A.
    radio navigation
    B.
    automatic landing equipment
    C.
    data communications
    D.
    all of the above

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  15. In an amplitude modulated waveform, the amplitude of the sideband is

  16. A.
    independent of the carrier amplitude
    B.
    independent of the modulation index
    C.
    carrier amplitude x modulation index
    D.
    1/2 carrier amplitude x modulation index

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  17. In communication systems the frequency range used for voice is

  18. A.
    15 Hz to 150 Hz
    B.
    30 Hz to 1000 Hz
    C.
    100 Hz to 1500 Hz
    D.
    300 Hz to 3800 Hz

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  19. In a radio receiver with simple AGC

  20. A.
    the highest AGC voltage is produced between stations
    B.
    an increase in signal strength produces more AGC
    C.
    the audio stage gain is normally controlled by AGC
    D.
    the faster the time constant of AGC, more accurate the output

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