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ECE Objective Questions { Analog Communication System }

64. Tick mark the false statement (s). In the spectrum of frequency-modulated wave
A. the carrier frequency disappears when the modulation index is large
B. the amplitude of any sideband depends on the modulation index
C. the total number of sidebands depends on the modulation index
D. the carrier frequency cannot disappear

65. An FM signal with a modulation index m1 is passed through a frequency tripler. The wave in the output of the tripler will have a modulationindex of
A. m1/3
B. mf
C. 3 mf
D. 9 mf

66. Typical transmitted power of an FDMFM microwave L.O.S. system is
A. 1 W
B. 100 W
C. 10 kW
D. 100 kW

67. Which one of the following methods cannot be used for suppressing unwanted side bands in SSB?
A. phase-shift method
B. balanced modulator
C. 'third' method
D. filter method

68. In the pilot-carrier system of modulation
A. a pilot-carrier is transmitted with the wanted sideband upper
B. sideband is suppressed but full carrier is allowed
C. two independent sidebands are allowed with attenuated carrier
D. it is necessary to employ transmitters and receivers of excellent frequency stability

69. In S.S.B., the transmitter suppresses
A. carrier and audio frequency
B. audio and one of the side band frequency
C. carrier and one of the side band frequencies.
D. None of above

70. Vestigial sideband (VSB) transmission is exclusively used for
A. HF mobile communications
B. video transmission in all TV systems to conserve bandwidth
C. long-distance HF radiotelephony
D. point-to-point radiotelephony where more than one channel is required

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