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ECE Objective Questions { Antenna }

15. Top-loading is sometimes used with an antenna is order to
A. decrease its input impedance
B. increase its height
C. decrease its radiation resistance
D. increase its effective height

16. One of the main reasons why dielectric lens antennas are preferred to parabolic reflector is that they
A. have no primary antenna mount to obstruct radiations
B. can be zoned to reduce weight
C. have low dielectric losses
D. have large frequency range

17. The radiation pattern of a parabolic antenna is
A. omni-directional
B. a figure of eight
C. highly directional
D. None of the above

18. Which of the following term does not apply to a discone antenna?
A. broadband
B. unidirectional
C. omnidirectional
D. constant-angle

19. The radiation pattern of Hertzian dipole in the plane perpendicular to the dipole is a
A. null
B. circle
C. figure of eight
D. none of the above

20. Consider an isotropic radiator radiating a power of 1 watt. At a distance of 1 metre, the power per unit area will equal W/m2.
B. 4n
C. 1/4n
D. 2n

21. A Yagi antenna is used for
A. very large bandwidth
B. high forward gain
C. omnidirectional gain
D. All the above

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