101. A carrier A cos ωct is modulated by a signal f(t) = 2 cos 10⁴. 2πt + 5 cos 10³. 2πt + 3 cos 10⁴. 4πt, then the bandwidth of the FM signal will be—
     (Given that, kf = 15 × 10³ Hz per volt)

1. 1. 170 kHz
      
      

   
   
   

   2. 190 kHz
      

   
   
   

   3. 210 kHz
      

   
   
   

   4. 150 kHz

   
   
   

---

1. View Hint View Answer Discuss in Forum

   We know that bandwidth of FM modulated signal is given by
   

   BW = 2(β + 1)fm =2Δf		1 +	1
   			β

   
   Here, the maximum frequency component in f (t) is 20 kHz, and the maximum amplitude present in f (t) is 5 volt.
   Therefore the frequency deviation Δf is given by
   Δf = K_f ·A_m = 15 × 10³ × 5 = 75 kHz
   and the modulation index β is given by
   

   β =	Δf	=	75 kHz	=	7.5	= 3.75
   	fm		20kHz		2

   
   Now, BW = 2 (β + 1) f_m = 2(3·75 + 1) 20 kHz
   = 9·5 × 20 kHz = 190 kHz
   Hence alternative (B) is the correct choice.

   Correct Option: B

   We know that bandwidth of FM modulated signal is given by
   

   BW = 2(β + 1)fm =2Δf		1 +	1
   			β

   
   Here, the maximum frequency component in f (t) is 20 kHz, and the maximum amplitude present in f (t) is 5 volt.
   Therefore the frequency deviation Δf is given by
   Δf = K_f ·A_m = 15 × 10³ × 5 = 75 kHz
   and the modulation index β is given by
   

   β =	Δf	=	75 kHz	=	7.5	= 3.75
   	fm		20kHz		2

   
   Now, BW = 2 (β + 1) f_m = 2(3·75 + 1) 20 kHz
   = 9·5 × 20 kHz = 190 kHz
   Hence alternative (B) is the correct choice.

---

102. Following is not advantage of FM over AM—

1. 1. noise immunity
      

   
   
   

   2. fidelity
      

   
   
   

   3. capture effect
      

   
   
   

   4. spluttering effect
      

   
   
   

---

1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

---

---

103. The message carrying efficiency is best in—

1. 1. FM
      
      

   
   
   

   2. AM
      

   
   
   

   3. AM-SC
      

   
   
   

   4. Phase modulation

   
   
   

---

1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

---

104. Which one is an advantage of AM over FM?

1. 1. FM is more immune to noise

   
   
   

   2. FM has better fidelity

   
   
   

   3. In a given frequency space, FM accommodates less number of channels as compared to AM

   
   
   

   4. FM has wide bandwidth

   
   
   

---

1. View Hint View Answer Discuss in Forum

   The main advantage of AM over FM is that in a given frequency space, FM accommodates less number of channels as compared to AM.

   Correct Option: C

   The main advantage of AM over FM is that in a given frequency space, FM accommodates less number of channels as compared to AM.

---

---

105. Figure of merit is always unity in—

1. 1. SSB-SC

   
   
   

   2. AM

   
   
   

   3. FM

   
   
   

   4. All

   
   
   

---

1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: A

   NA

---