56. At microwave frequencies, the size of the antenna becomes:
    

1. 1. Very large
      

   
   
   

   2. Large
      

   
   
   

   3. Small
      
      

   
   
   

   4. Very small

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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57. Which of the following noise becomes important at microwave frequencies?
    

1. 1. Short noise
      

   
   
   

   2. Flicker noise
      

   
   
   

   3. Thermal noise
      

   
   
   

   4. Transit time noise

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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58. Due to curvature of earth, microwave repeaters are placed at distance of about:
    

1. 1. 10 km
      

   
   
   

   2. 50 km
      

   
   
   

   3. 150 km
      

   
   
   

   4. 250 km
      

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

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59. The advantage of microwave lower frequency signals are:
    

1. 1. Increased bandwidth
      

   
   
   

   2. Ability to use high gain, directivity antenna
      

   
   
   

   3. Greater secrecy
      

   
   
   

   4. All of the above

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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60. The front end of an amplifier chain in manufacture of communication system is kept immersed in liquid nitrogen, to:
    

1. 1. Dissipate heat generated by amplifier
      

   
   
   

   2. Expand its frequency response
      

   
   
   

   3. Improve its noise figure
      

   
   
   

   4. Reduce the distortion by the amplifier

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

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