8. Modulation is the process of
A. generating constant-frequency radio waves
B. combining audio and radio-frequency waves at the transmitting end of a communication system
C.reducing distortion in RF amplifiers
D.improving thermal stability of a transistor
9. Regarding amplitude modulation, which statement is false?
A.amplitude of carrier wave is varied by the signal voltage
B.frequency of carrier wave remains unchanged
C. outline of the modulated carrier wave is different in shape from the modulating wave
D.amplitude of the modulated wave varies at frequency equal to the frequency of the modulating signal
10. Maximum undistorted power output of a transmitter is obtained when its modulation is-percent.
A. more than 100
C. less than 100
11. The noise performance of a square-law demodulator ofAM signal is
A. better than that of an envelope detector
B. better than that of a synchronous detector
C.idential with that of a synchronous detector
D.poorer than that detector
12. If in a broadcasting studio, a 1000 kHz carrier is modulated by an audio signal of frequency range 100 - 5000 Hz, the width of channel is- kHz.
13. For a signal amplitude modulated to a depth of 100% by a sinusoidal signal, the power is?the power of unmodulated carrier.
A. same as
B. twice as
C. ?2 times
14. A transmitter supplies 10 kW of carrier power to the antenna. The total radiated power with 40% modulation is ?kW./
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