71. In radio broadcasting, rhombic antennas are used for
A. short distance broad casting
B. long distance directional broadcasting
C. uniform coverage round an antenna
D. none of above

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72. The reverberation time (R/T) of a normal talk studio is around ? second.
A.0.2
B.0.4
C.0.7
D.1

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73. Geo-stationary satellite is located above surface of Earth at a distance of about _____ km.
A.6,000
B.36,000
C.3,600
D.600

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74. Transistor was invented in the
A. BBC research Laboratory
B. `IsIHK' Research Laboratory in Japan
C. Bell Telephone Laboratory in USA
D. Tata Institute of Fundamental Research in India

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75. The reverberation time of a broadcast studio for music, having a volume of 160 cubic metre, is of the order of ___ second.
A.0.2
B.0.5
C.1.5
D.3

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76. Which of the following materials has the highest absorption coefficient for sound waves?
A. copper plate
B. celotex
C. teakply
D. alnico

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77. Modulation is used for
A. transmitting intelligence over long distances
B. reducing the bandwidth of transmission
C. allowing the use of cheaper tubes
D. none of above

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