Tuesday, September 1, 2020

Chapter 3 : Electromagnetism - Page 6

Chapter 3 : Electromagnetism

51. An isotropic radiator is one which short circuited impedance is to Yagi antenna is
A. parasitic element
B. low cost
C. folded dipole
D. good bandwidth


... Answer is (D)

 

 
 

52. The term which does not apply range. It is best to use

 
A. a double stub
B. broad-band directional coupler
C. a balun transformer
D. a single stub of adjustable position

... Answer is (B)

 
 
 

53. Antenna reciprocity is used in

A. aircraft instrumentation
B. multiplex tele metry

C. radio broadcast
D. TV broadcast

... Answer is (C)

 

 
 

54. In faraday rotation, the polarization phenomenon

A. exists along the perpendicular direction
B. exists along the axis of the array

C.
does not exist
D. is non-reciprocal

  ... Answer is (D)

 

 
 
55. For a plane good conductor, skin depth varies
  ...
Answer is (D)

 
 
 

56. Skip distance is
A.
(3x10⁸)/(f(Hₛ) meters
B.
(3x10⁸)/(f/2(Hₛ) meters
C.
the minimum distance from the transmitter at which a stay wave of a given frequency is returned to earth from the ionosphere
D. the maximum distance from the transmitter at which a sky wave of a given frequency is returned to earth from the ionosphere
.

  ... Answer is (A)

 

 
 

57. EM waves in the frequency range 300 MHz to 30 GHz can be best transmitted using

A. Groundwave propagation
B. Duct propagation
C. sky wave propagation
D. none of these

... Answer is (B)

 
 

58.. Parabolic antenna is used at

A. short waves
B. microwaves

C.
long waves
D. medium waves

... Answer is (B)

 
 

59. Circularly polarized antenna is

A. helical
B. log periodic
C. Yagi
D. shombic
 
  ... Answer is (A)

 
 

60. In an end fire array, maximum radiation occurs


A.
long the array
D. perpendicular to the array

C.
at 30° to the array
D. at 45° to the array

  ... Answer is (A)

 

 

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