126. VLF waves are used for some types of services because—

1. 1. Of the low powers required

   
   
   

   2. The transmitting antennas are of convenient size

   
   
   

   3. They are very reliable

   
   
   

   4. They penetrate the ionosphere easily

   
   
   

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1. View Hint View Answer Discuss in Forum

   VLF waves are used for some types of services because they are very reliable.

   Correct Option: C

   VLF waves are used for some types of services because they are very reliable.

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127. Indicate which one of the following terms applies to troposcatter propagation—

1. 1. SIDs

   
   
   

   2. Fading

   
   
   

   3. Atmospheric storms

   
   
   

   4. Faraday rotation

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

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128. To couple a coaxial line to a parallel-wire line, it is best to use a—

1. 1. Slotted line

   
   
   

   2. Balun

   
   
   

   3. Directional Coupler

   
   
   

   4. Quarter-wave transformer

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

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129. The main disadvantage of the two-hole directional coupler is—

1. 1. Low directional coupling

   
   
   

   2. Poor directivity

   
   
   

   3. High SWR

   
   
   

   4. Narrow bandwidth

   
   
   

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1. View Hint View Answer Discuss in Forum

   The main disadvantage of the two-hole directional coupler is narrow bandwidth.
   

   Correct Option: D

   The main disadvantage of the two-hole directional coupler is narrow bandwidth.
   

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130. For transmission-line load matching over a range of frequencies, it is best to use a—

1. 1. Balun

   
   
   

   2. Broadband directional coupler

   
   
   

   3. Double stub

   
   
   

   4. Single stub of adjustable position

   
   
   

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1. View Hint View Answer Discuss in Forum

   For transmission-line load matching over a range of frequencies, it is best to use a double stub.
   

   Correct Option: C

   For transmission-line load matching over a range of frequencies, it is best to use a double stub.
   

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