51. A reflex klystron functions as:
    

1. 1. Microwave oscillator
      

   
   
   

   2. Microwave amplifier
      

   
   
   

   3. Both as microwave amplifier and oscillator
      

   
   
   

   4. A high gain cavity

   
   
   

---

1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: A

   NA

---

52. Multicavity klystron:
    

1. 1. Is not a microwave device

   
   
   

   2. In not a good low level amplifier because of noise

   
   
   

   3. Is not suited for pulse operation

   
   
   

   4. Has a high repeller voltage to ensure small transit time

   
   
   

---

1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

---

---

53. Dither-tuned magnetrons:
    

1. 1. Can be easily jammed
      

   
   
   

   2. Can send pulses on one frequency only
      

   
   
   

   3. Operates on a fixed frequency
      

   
   
   

   4. May be conventional or coaxial

   
   
   

---

1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

---

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

1. 1. Very large
      

   
   
   

   2. Large
      

   
   
   

   3. Small
      
      

   
   
   

   4. Very small

   
   
   

---

1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

---

---

55. 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
      

   
   
   

---

1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

---