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

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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

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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

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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

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68. Frequenices in UHF range propagate by means of?waves.
A. ground
B. sky
C. space
D. surface

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69. Trposcatter system capacity than line-of-sight microwave system.
A. more
B. less
C. same
D. none of the above

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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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