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Electronics Engineering Objective Questions { Antenna }

127. Cassegrain feed is used with a parabolic reflector to
A. reduce the size of the main reflector
B. increase the gain of the system
C. increase the beam width of the system
D. allow the feed to be placed at a convenient point
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128. Zoning is used with adielectric antenna in order to
A. permit pin-point focusing
B. reduce the bulk of the lens
C. increase the bandwidth of the lens
D. correct the curvature of the wave front from a horn that is too short
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129. The numbered statements at the left are to be matched with the lettered statements at the right(1) Sky wave-(a) Parasitic element,(2) Antenna feed-(b) Delta match,(3) Reflector-(c) Long-wire antenna,(4) Rhombic antenna (d) Ionosphere Which of the following represents the correct matching :
A. 1 ? a, 2 ? c, 3 ? d, 4 ? b
B. 1 ? b, 2 ? a, 3 ? d, 4 ? c
C. 1 ? c, 2 ? b, 3 ? c, 4 ? d
D. 1 ? d, 2 ? b, 3 ? a, 4 ? c
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130. The null of a loop antenna occurs with
A. a broadside signal
B. a signal off the ends
C. either of (a) or (b) above
D. none of the above
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131. A half wave dipole has maximum response in
A. broadside direction
B. off the ends
C. either of (a) or (b) above
D. none of the above
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132. The night effect is most prominent in
A. adcock antenna
B. loop antenna
C. vertical antenna
D. none of the above
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133. Which of the following statement is true?
A. A parasitic reflector is in the front of the dipole
B. The director is always in the back of the dipole
C. A Yagi antenna uses a reflector and directors
D. A reflector cannot be used with a folded dipole
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