64. A ship-to-ship communication system is plagued by fading. The best solution seems to be the use of
A. a broadband antenna
B. a more directional antenna
C. space diversity
D. frequency diversity
65. Free space loss suffered by a icrowave signal for a hop length d is a function of
A. d112
B.d
C. d2
D. d3
66. Diffraction of electromagnetic waves
A. is caused by reflection from the ground
B. arises only with spherical wavefronts
C. will occur when the wave pass through a large slot
D. may occur around the edge of a sharp obstacle
67. The absorption of radiowaves by atmosphere depends on
A. their frequency
B. their distance from the transmitter
C. the polarization of the waves
D. the polarization of the atmosphere
68. Frequenices in UHF range propagate by means of?waves.
A. ground
B. sky
C. space
D. surface
69. Trposcatter system capacity than line-of-sight microwave system.
A. more
B. less
C. same
D. none of the above
70. A non-degenarate parametric amplifier has an input frequency fi and pump frequency fp. The idler frequency is
A. fp fi
B.fi
C. 2 fi
D. f ? fp
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