121. A ship-to-ship communications system is plagued by fading. The best solution seems to be the use of—

1. 1. A more directional antenna

   
   
   

   2. A broadband antenna

   
   
   

   3. Frequency diversity

   
   
   

   4. Space diversity

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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122. Distances near the skip distance should be used for sky-wave propagation—
     

1. 1. To avoid tilting

   
   
   

   2. To prevent sky-wave and upper ray interference

   
   
   

   3. To avoid the Faraday effect

   
   
   

   4. So as not to exceed the critical frequency
      

   
   
   

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1. View Hint View Answer Discuss in Forum

   Distances near the skip distance should be used for sky-wave propagation to prevent sky-wave and upper ray interference
   

   Correct Option: B

   Distances near the skip distance should be used for sky-wave propagation to prevent sky-wave and upper ray interference
   

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123. High-frequency waves are—

1. 1. Absorbed by the F2 layer

   
   
   

   2. Reflected by the D layer

   
   
   

   3. Capable of use for long-distance communications on the moon

   
   
   

   4. Affected by the solar cycle

   
   
   

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1. View Hint View Answer Discuss in Forum

   High-frequency waves are affected by the solar cycle.

   Correct Option: D

   High-frequency waves are affected by the solar cycle.

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124. Indicate which of the following frequencies cannot be used for reliable beyond the horizon terrestrial communications without repeaters?
     

1. 1. 20 kHz

   
   
   

   2. 15 MHz

   
   
   

   3. 900 MHz

   
   
   

   4. 12 GHz

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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125. Indicate which of the following frequencies cannot be used for reliable beyond the horizon terrestrial communications without repeaters?
     

1. 1. 20 kHz

   
   
   

   2. 15 MHz

   
   
   

   3. 900 MHz

   
   
   

   4. 12 GHz

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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