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ECE Objective Questions { Analog Communication System }

113. When the modulation index of an amplitude modulated wave is changed from 0 to 1, the transmitted power will
A. remain unchanged
B. decrease by 50%
C. increase by 50%
D. increase by 100%

114. Which one of the following cannot be used to remove the unwanted side band in SSB?
A. Phase shift devices
B. Balanced modulator
C. Filters
D. All of the above

115. If Em be the peak value of the modulating voltage and Er be the peak value of carrier voltage, then modulation index, is given by
A. M = K EmEr
B. M = K Em
C. M K ?Er
D. M = K E

116. A balanced modulator circuit uses
A. two identical diodes
B. two identical triodes
C. two diodes with different V-1 characteristics
D. two triodes with different V-I characteristics

117. A CW transmitter radiates
A. modulated RF carrier
B. unmodulated RF carrier
C. both (a) and (b) above
D. none of the above

118. A buffer amplifier is
A. a double-tuned amplifier
B. a high gain dc amplifier
C. a cathode follower stage
D. none of the above

119. A 3A modulation is sometimes used to
A. allow thereceiver to have a frequency synthesizer
B. reduce the bandwidth required for transmission
C. reduce the power that must be transmitted
D. simplify the frequency stability problem in reception

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