Analog Communication Test Questions - Set 2

1)   Calculate the power in one of the side band in SSBSC modulation when the carrier power is 124W and there is 80% modulation depth in the amplitude modulated signal.

a. 89.33 W
b. 64.85 W
c. 79.36 W
d. 102 W
Answer  Explanation 

ANSWER: 79.36 W

Explanation:
No explanation is available for this question!


2)   Calculate the total modulation Index when a carrier wave is being modulated by two modulating signals with modulation indices 0.8 and 0.3.

a. 0.8544
b. 0.6788
c. 0.9999
d. 0.5545
Answer  Explanation 

ANSWER: 0.8544

Explanation:
No explanation is available for this question!


3)   Calculate the frequencies available in the frequency spectrum when a 2MHz carrier is modulated by two sinusoidal signals of 350Hz and 600Hz.

a. 2000.35, 1999.65 and 2000.6, 1999.4
b. 1999.35, 1999.65 and 2000.6, 2000.4
c. 2000.35, 2000.65 and 2000.6, 2000.4
d. 1999.35, 1999.65 and 1999.6, 1999.4
Answer  Explanation 

ANSWER: 2000.35, 1999.65 and 2000.6, 1999.4

Explanation:
No explanation is available for this question!


4)   An AM signal has a total power of 48 Watts with 45% modulation. Calculate the power in the carrier and the sidebands.

a. 39.59 W, 4.505 W
b. 40.59 W, 4.205 W
c. 43.59 W, 2.205 W
d. 31.59 W, 8.205 W
Answer  Explanation 

ANSWER: 43.59 W, 2.205 W

Explanation:
No explanation is available for this question!


5)   Calculate the power saved in an Amplitude Modulated wave when it is transmitted with 45% modulation
- Without carrier
- Without carrier and a sideband


a. 90%, 95%
b. 82%, 91%
c. 82%, 18%
d. 68%, 16%
Answer  Explanation 

ANSWER: 90%, 95%

Explanation:
No explanation is available for this question!


6)   What is the carrier frequency in an AM wave when its highest frequency component is 850Hz and the bandwidth of the signal is 50Hz?

a. 80 Hz
b. 695 Hz
c. 625 Hz
d. 825 Hz
Answer  Explanation 

ANSWER: 825 Hz

Explanation:
No explanation is available for this question!


7)   Noise figure of merit in SSB modulated signal is

a. 1
b. Less than 1
c. Greater than 1
d. None of the above
Answer  Explanation 

ANSWER: 1

Explanation:
No explanation is available for this question!


8)   For low level modulation, amplifier used is

a. Class A
b. Class C
c. Class A & C
d. None of the above
Answer  Explanation 

ANSWER: Class A

Explanation:
No explanation is available for this question!


9)   The antenna current of the transmitter is 10A. Find the percentage of modulation when the antenna current increases to 10.4A.

a. 32%
b. 28.5%
c. 64%
d. 40%
Answer  Explanation 

ANSWER: 28.5%

Explanation:
No explanation is available for this question!


10)   What is the change in the value of transmitted power when the modulation index changes from 0 to 1?

a. 100%
b. Remains unchanged
c. 50%
d. 80%
Answer  Explanation 

ANSWER: 50%

Explanation:
No explanation is available for this question!


11)   Function of RF mixer is

a. Addition of two signals
b. Multiplication of two signals
c. Rejection of noise
d. None of the above
Answer  Explanation 

ANSWER: Multiplication of two signals

Explanation:
No explanation is available for this question!


12)   If a receiver has poor capacity of blocking adjacent channel interference then the receiver has

a. Poor selectivity
b. Poor Signal to noise ratio
c. Poor sensitivity
d. None of the above
Answer  Explanation 

ANSWER: Poor selectivity

Explanation:
No explanation is available for this question!


13)   Advantage of using a high frequency carrier wave is

a. Signal can be transmitted over very long distances
b. Dissipates very small power
c. Antenna height of the transmitter is reduced
d. All of the above
Answer  Explanation 

ANSWER: All of the above

Explanation:
No explanation is available for this question!


14)   Advantage of using VSB transmission is

a. Higher bandwidth than SSB
b. Less power required as compared to DSBSC
c. Both a and b
d. None of the above
Answer  Explanation 

ANSWER: Both a and b

Explanation:
No explanation is available for this question!


15)   Modulation is required for

a. Reducing noise while transmission
b. Multiplexing the signals
c. Reduction of Antenna height
d. Reduction in the complexity of circuitry
e. All of the above
Answer  Explanation 

ANSWER: All of the above

Explanation:
No explanation is available for this question!


16)   For over modulation, the value of modulation index m is

a. m < 1
b. m = 1
c. m > 1
d. Not predetermined
Answer  Explanation 

ANSWER: m > 1

Explanation:
No explanation is available for this question!


17)   Demodulation is:

a. Detection
b. Recovering information from modulated signal
c. Both a and b
d. None of the above
Answer  Explanation 

ANSWER: Both a and b

Explanation:
No explanation is available for this question!


18)   Calculate the side band power in an SSBSC signal when there is 50% modulation and the carrier power is 50W.

a. 50 W
b. 25 W
c. 6.25 W
d. 12.5 W
Answer  Explanation 

ANSWER: 6.25 W

Explanation:
No explanation is available for this question!


19)   TRF receiver and super heterodyne receiver are used for

a. Detection of modulating signal
b. Removal of unwanted signal
c. Both a and b
d. None of the above
Answer  Explanation 

ANSWER: Both a and b

Explanation:
No explanation is available for this question!


20)   Disadvantage of using a DSB or SSB signal modulation is

a. Difficult to recover information at the receiver
b. Carrier has to be locally generated at receiver
c. Both a and b are correct
d. None of the above
Answer  Explanation 

ANSWER: Both a and b are correct

Explanation:
No explanation is available for this question!