71. Rain drop attenuation in most microwave communication links is caused due to:
    

1. 1. Scattering of microwaves by water drops of specific size
      

   
   
   

   2. Scattering of microwaves by a collection of droplets acting as a single body
      

   
   
   

   3. Absorption of microwave by water and consequent heating of the liquid
      

   
   
   

   4. Absorption of microwaves by water-vapour in the atmosphere

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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72. The semiconductor diode which can be used in switching circuits at microwave range is:
    
    

1. 1. PIN diode
      

   
   
   

   2. Tunnel diode
      

   
   
   

   3. Varactor diode
      

   
   
   

   4. Gunn diode

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: A

   NA

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73. HEMT used in the microwave circuit is a:
    

1. 1. Source
      

   
   
   

   2. High power amplifier
      

   
   
   

   3. Detector
      

   
   
   

   4. Low noise amplifier

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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74. Wave guides are pressurised above normal atmospheric pressure for:
    

1. 1. Increasing their power handling capacity
      

   
   
   

   2. Improving the conductivity of their walls
      

   
   
   

   3. Preventing higher order modes from propagating
      

   
   
   

   4. Varying the wave impedence
      

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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75. The main advantage of the two hole directional coupler is:
    

1. 1. Low directional coupling
      

   
   
   

   2. High SWR
      

   
   
   

   3. Poor directivity
      

   
   
   

   4. Narrow bandwidth

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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