Discussion
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- Question
Radio broadcasts are generally
Options- A. amplitude modulation
- B. frequency modulation
- C. both amplitude and frequency modulation
- D. neither amplitude nor frequency modulation
- Correct Answer
- frequency modulation
ExplanationFrequency modulation gives noise free reception and is used for radio broadcasts.
Communication Systems problems
Search Results
- 1. Push pull amplifier is
Options- A. voltage amplifier
- B. current amplifier
- C. power amplifier
- D. none of the above Discuss
Correct Answer: power amplifier
Explanation:
Push pull is a power amplifier.- 2. 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:
.
- 3. 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.- 4. 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.- 5. 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.- 6. Non-coherently detection is not possible for
Options- A. PSK
- B. ASK
- C. FSK
- D. both (a) and (c) Discuss
Correct Answer: PSK
- 7. 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.- 8. 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.- 9. 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.- 10. Assertion (A): The phenomenon of differential mobility is called transferred electron effect.
Reason (R): GaAs exhibits transferred electron effect.
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 but R is not correct explanation of A
Explanation:
A Gunn diode uses GaAs which has a negative differential mobility, i.e., a decrease in carrier velocity with increase in electric field.This effects is called transferred electron effect. The impedance of a Gunn diode is tens of ohms.
A Gunn diode oscillator has a resonant cavity, an arrangement to couple Gunn diode to cavity, biasing arrangement for Gunn diode and arrangement to couple RF power to load.
Applications of Gunn diode oscillator include continuous wave radar, pulsed radar and microwave receivers.
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