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- Question
Push pull amplifier is
Options- A. voltage amplifier
- B. current amplifier
- C. power amplifier
- D. none of the above
- Correct Answer
- power amplifier
ExplanationPush pull is a power amplifier.
Communication Systems problems
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- 1. If the frequency of a wave 20 Hz, the time period is
Options- A. 20 secs
- B. 2 secs
- C. 0.2 secs
- D. 0.05 secs Discuss
Correct Answer: 0.05 secs
Explanation:
.
- 2. Assertion (A): Free space does not interfere with normal radiation and propagation of radio waves
Reason (R): Free space has no magnetic or gravitational fields.
Options- A. Both A and R are correct and R is correct explanation of A
- B. Both A and R are correct but R is not correct explanation of A
- C. A is correct but R is wrong
- D. A is wrong but R is correct Discuss
Correct Answer: Both A and R are correct and R is correct explanation of A
Explanation:
Since free space does not have magnetic and other fields, waves can propagate without any interference.- 3. Which of the following is the indirect way of FM generation?
Options- A. Reactance bipolar transistor modulator
- B. Armstrong modulator
- C. Varactor diode modulator
- D. Reactance FM modulator Discuss
Correct Answer: Armstrong modulator
Explanation:
It generates FM through phase modulation.- 4. For attenuation of high frequencies we should use
Options- A. shunt capacitance
- B. series capacitance
- C. inductance
- D. resistance Discuss
Correct Answer: shunt capacitance
Explanation:
Since Xc for high frequencies is low, the high frequencies are shunted to ground and are not transmitted.- 5. In standing wave pattern on a transmission line
Options- 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) Discuss
Correct Answer: voltage nodes and current antinodes as well as current nodes and voltage antinodes coincide
Explanation:
When standing wave is set up voltage maxima and current minima and voltage minima and current maxima coincide.- 6. Radio broadcasts are generally
Options- A. amplitude modulation
- B. frequency modulation
- C. both amplitude and frequency modulation
- D. neither amplitude nor frequency modulation Discuss
Correct Answer: frequency modulation
Explanation:
Frequency modulation gives noise free reception and is used for radio broadcasts.- 7. Non-coherently detection is not possible for
Options- A. PSK
- B. ASK
- C. FSK
- D. both (a) and (c) Discuss
Correct Answer: PSK
- 8. Energy content of atmospheric noise
Options- A. does not depend on frequency
- B. decreases as frequency is increased
- C. increases as frequency is increased
- D. either (a) or (c) depending on the temperature Discuss
Correct Answer: decreases as frequency is increased
Explanation:
Atmospheric noise decreases as frequency is increased.- 9. The range of a cordless telephone is about
Options- A. 1000 m
- B. 500 m
- C. 100 m
- D. 10 m Discuss
Correct Answer: 100 m
Explanation:
The range depends on quality of instrument and is about 100 m.- 10. VSB modulation is preferred in TV because
Options- A. it reduces the bandwidth requirement to half
- B. it avoids phase distortion at low frequencies
- C. it results in better reception
- D. none of the above Discuss
Correct Answer: it reduces the bandwidth requirement to half
Explanation:
VSB (vestigial side band) transmission transmits one side band fully and the other side band partially thus, reducing the bandwidth requirement.
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