Communication Systems - Section 1 (3)

Directions to Solve

Communication Systems - Section 1

17. 

A carrier wave carries information.
A. True
B. False

Answer: Option B

Explanation:

Carrier does not have any information.

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18. 

In the figure , the output y(t) will be
A. 534-934-3
B. 534-934-4
C. 534-934-5
D. 534-934-6

Answer: Option C

Explanation:

555-934-1

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19. 

If the bandwidth is increased by 2, the γFM γAM (where γ is the ratio of SNR of output to SNR at input, FM is frequency modulation and AM is amplitude modulation) is increased by a factor of
A. 2
B. 3
C. 4
D. 6

Answer: Option C

Explanation:

Doubling of frequency increase SNR in frequency modulation by 4. It has no effect in AM.

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20. 

In standing wave pattern on a transmission line
A. voltage and current nodes coincide
B. voltage and current antinodes coincide
C. voltage nodes and current antinodes as well as current nodes and voltage antinodes coincide
D. both (a) and (b)

Answer: Option C

Explanation:

When standing wave is set up voltage maxima and current minima and voltage minima and current maxima coincide.

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21. 

A 1000 kHz carrier is simultaneously modulated with 300 Hz, 800 Hz and 2 kHz audio sine waves. Which of the following frequency is least likely to be present in the output?
A. 1002 kHz
B. 1000 kHz
C. 999.2 kHz
D. 998.0 kHz

Answer: Option B

Explanation:

Frequency present in the sidebands is equal to = fc ± fm, fc ± 2fm , fc ± 3fm .

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22. 

A carrier is simultaneously modulated by two sine waves having modulation indices of 0.4 and 0.3. The total modulation index will be
A. 0.1
B. 0.7
C. 0.5
D. 0.35

Answer: Option

Explanation:

m1 = 0.4, m2 = 0.3

.

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23. 

Direct and reflected sound waves may interfere with each other.
A. True
B. False

Answer: Option B

Explanation:

PAS use moving coil microphones.

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24. 

Some types of traps used in video IF amplifier of colour TV are
A. shunt traps
B. series traps
C. absorption traps
D. all of the above

Answer: Option D

Explanation:

All these are used.

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