71. Indicate which of the following system is digital pulse? modulation.
A. position
B. code
C. width
D. frequency

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72. The main disadvantage of the two-hole directional coupler is
A. low directional coupling
B. poor directivity
C. high SWR
D. narrow bandwidth

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73.  Indicate the false statement. SWR on a transmission line is infinity; the line is terminated in a/an
A. short circuit
B. complex impedance
C. open circuit
D. pure reactance

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74. One of the following types of noise becomes of great importance at high frequencies. It is the?noise
A. shot
B. agitation
C. flicker
D. transit?time

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75. To provide two or more voice circuits for the same carrier, it is possible to use
A. ISB
B. carrier reinsertion
C. SSB with pilot carrier
D. SSB with carrier suppressed

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76. When microwave signals follow the curvature of the Earth, this is known as
A. the Faraday effect
B. ducting
C. tropospheric scatter
D. ionospheric reflection

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77. When the modulating frequency is doubled, the modulation index is halved and the modulating voltage remains constant. The modulation system is
A. amplitude modulation
B. phase modulation
C. frequency modulation
D. any one of the three

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