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

1. 1. TM₀₁
      

   
   
   

   2. TE₀₁
      

   
   
   

   3. TM₁₁
      

   
   
   

   4. TE₁₁

   
   
   

---

1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: A

   NA

---

22. Two perfect 4-port circulators are cascaded, as shown in fig. to form a 6-port circulator.
    Transmitter (T), receiver (R) antenna (A) and match load (L) are connected to these ports. Which one of the following interconnection schemes is correct?
    
    
    

1. 1. T  R  A   L
      4  5  6   1,2,3

   
   
   

   2. T  R  A   L
      3  5  6   1,2,4

   
   
   

   3. T  R  A   L
      2  3  4   1,5,6

   
   
   

   4. T  R  A   L
      1  3  2   ;4,5,6

   
   
   

---

1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: A

   NA

---

---

23. Consider the following statements regarding a cavity wavemeter in a reaction type of circuit as shown in Fig.
    1. The distance d is made either zero or approximately a guide half-wave length, so that an effective short circuit appears at the waveguide wall when the cavity is at resonance.
    2. A dip in the load power occurs as the wavemeter is tuned through resonance.
    3. The magnitude of the cavity impedance depends only on the distance d.
    4. The magnitude of the power dip depends only on the Q of the cavity.
    
    
    
    

1. 1. 1 alone is correct
      

   
   
   

   2. 2 alone is correct
      

   
   
   

   3. 1 and 3 are correct
      

   
   
   

   4. 2 and 4 are correct

   
   
   

---

1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

---

24. Match List-I with List-II and select the correct answer using the codes given below the lists:
    

    List-I	List-II
    A. Periscope Antenna	1. Circular Polarisation
    B. Helical Antenna	2. Scanning radar
    C. Monopulse antenna	3. Communication Satellite
    D. Transponder	4. Television transmission		5. Microwave link

    
    

1. 1. A B C D
      1 2 3 4
      

   
   
   

   2. A B C D
      2 3 4 5
      

   
   
   

   3. A B C D
      3 5 2 4
      

   
   
   

   4. A B C D
      5 1 2 3

   
   
   

---

1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

---

---

25. In a travelling-wave tube, the phase velocity of the axial component of the rf field on the slow-wave structure is kept:
    

1. 1. Equal to the velocity of the electrons
      
      

   
   
   

   2. Slightly less than the velocity of electrons
      

   
   
   

   3. Slightly more than the velocity of electrons
      

   
   
   

   4. Equal to the velocity of light in free space

   
   
   

---

1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

---