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