57. In the spectrum of a frequency modulated wave
A. the carrier frequency disappears when the modulation index is large
B. the amplitude of any sideband depends on the modulation index
C. the total number of sidebands depends on the modulation index
D. the carrier frequency cannot disappew

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58. Indicate the FALSE statement. Modulation is used to
A. reduce the bandwidth used
B. separate differing transmissions
C. ensure that intelligence may be transmitted over long distance
D. allow the use of practicable antennas

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59. The most common modulation system used for radio telegraphys is
A. pulse-code modulation
B. frequency-shift keying
C. single-tone modulation
D. two-tone modulation

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60. Indicate which one of the following is NOT an advantage of FM over AM
A. better noise immunity is provided
B. lower bandwidth is required
C. the transmitted power is more useful
D. less modulation power is required

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61. Short wave broadcasting uses _____ wave.
A. ground
B. ionospheric
C. direct
D. none of the above

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62. To prevent reflection effect on a hop, it is best to ensure that the terrain between the antennas is
A. plain
B. water surface
C. forested
D. telted

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63.  Microwave link repeaters are typically 50 km apart
A. because of atmospheric attenuation
B. because of the Earth's curvature
C. because of output tube power limitations
D. to ensure that the applied dc voltage is not excessive

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