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ECE Objective Questions { Analog Communication System }



78. Which of the following frequency is likely to be a3sociated with AM radio broadcast?
A. 1000 kHz
B.100 MHz
C. 500 MHz
D. 10 GHz

79. When El, E2, E3 etc. are the simultaneous modulating voltages, then the total modulating voltage Et will be
A.Et= El+ E2 + E3 +
B. Et= E12 + E22 E32
C. Et = 'E E32
D.E1 + E2 + E3 +

80. A transmitter radiates 9 kW with the carrier unmodulated and 10.125 kW when the carrier is sinusoidally modulated. The modulation index will be
A.40%
B.44%
C.50%
D.66%

81. If another sine wave, corresponding to 40% modulation, is transmitted simultaneously, determine the total radiated power
A. 9.9 kW
B. 10 kW
C. 10.42 kW
D. 10.84 kW

82. When a broadcast AM transmitter is 50% modulated, its antenna current is 12 A. What will be the current when the modulation depth is increased to 90%?
A. 12.9A
B. 13.4 A
C. 16.6 A
D.21.8A

83. In amplitude modulation, the carrier and the modulating voltages are given by e = E sin co c c mt em = Em sin comt.The modulation index will beE 1E2 + E2E3+ E3E4+(d) Et ? (a) One of the waves is not pure sine wave
A.(b) The modulation index is 0.5
B. The modulation index is 1.0
C. The output wave is distorted
D.

84. The ratio of the total power in amplitude modulated wave to the unmodulated carrier power is given by
A.(a)= 1--
B. = = - -Pt Pc2Pc2m2-P,
C. =1+ - = -1471712Pc2Pc
D.

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