101. Consider the following statements regarding feed which is the Key component of a reflector antenna as it has a decisive bearing on the overall-performance:
     1. For a horn-feed antenna the reflector focus must coincide with horn-feeds phase centre, which for a wide-flare horn lies in the plane of horn aperture.
     2. The feed must have minimal radiation outside the angular aperture of reflector.
     3. In print focus or cassegrain systems, the main or sub-reflectors should be in Fraunhofer zone of the feed antenna.
     Which of the statements are correct?
     

1. 1. 1, 2 and 3
      

   
   
   

   2. 1 and 2
      

   
   
   

   3. 2 and 3
      

   
   
   

   4. 1 and 3

   
   
   

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   NA

   Correct Option: A

   NA

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102. A calorimetric measurement for average power of a signal gave a value of 400 W. The value was interpreted for peak power as 0·5 mW. Then the duty cycle of the signal is:
     

1. 1. 0·08%
      

   
   
   

   2. 8%
      

   
   
   

   3. 40%
      

   
   
   

   4. 80%

   
   
   

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   NA

   Correct Option: A

   NA

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103. Radiation from a helical antenna is:
     

1. 1. Plane polarised
      

   
   
   

   2. Partially plane polarised
      

   
   
   

   3. Circularly polarised
      

   
   
   

   4. Elliptically polarised
      

   
   
   

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   NA

   Correct Option: C

   NA

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104. Consider the following statements:
     In a magic Tee,
     1. Collinear arms are isolated from each other.
     2. One of the collinear arms is isolated from E-arm.
     3. The collinear arms is isolated from H-arm.
     4. E-arm and H-arm are isolated from each other of these statements, correct answers are:
     

1. 1. 1 and 2
      

   
   
   

   2. 1 and 3
      

   
   
   

   3. 1 and 4
      

   
   
   

   4. 2 and 3

   
   
   

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   NA

   Correct Option: C

   NA

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105. In a circular waveguide with radius ‘r’, the dominant mode is:
     

1. 1. TM₀₁
      

   
   
   

   2. TE₀₁
      

   
   
   

   3. TM₁₁
      

   
   
   

   4. TE₁₁

   
   
   

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   NA

   Correct Option: A

   NA

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