Discussion
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- Question
In FM signal with a modulation index mf is passed through a frequency tripler. The wave in the output of the tripler will have a modulation index of
Options- A. mf
- B. 3mf
- C. mf/3
- D. mf/9
- Correct Answer
- 3mf
ExplanationFrequency multiplier increase the deviation,
.
Communication Systems problems
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- 1. It is desired that transmission line and load should match for a range of frequencies. The best method is
Options- A. to use a balun
- B. to use a single stub of adjustable position
- C. to use a double stub
- D. to use a broad band amplifier Discuss
Correct Answer: to use a double stub
Explanation:
When matching over a range of frequencies is desired, double stub is necessary.- 2. In the figure
, the output y(t) will be 
Options- A.
- B.
- C.
- D.
Discuss
Correct Answer:
Explanation:
- 3. A telephone exchange has 9000 subscribers. If the number of calls originating at peak time is 10, 000 in one hour, the calling rate is
Options- A. 0.9
- B. 10/9
- C. 0.81
- D. 0.1 Discuss
Correct Answer: 10/9
Explanation:
Calling rate is the number of calls per subscriber.- 4. The rate at which information can be carried through a communication channel depends on
Options- A. carrier frequency
- B. bandwidth
- C. transmission loss
- D. transmitted power Discuss
Correct Answer: bandwidth
Explanation:
Rate of information depends on bandwidth.- 5. In a fascimile reproduction time to scan one line is 2 ms. If it has 4% blanking, the visible trace time is
Options- A. 1.92 ms
- B. 2.08 ms
- C. 50 ms
- D. 0.08 ms Discuss
Correct Answer: 1.92 ms
Explanation:
(2 ms) (1 - 0.04) = 1.92 ms.- 6. Direct and reflected sound waves may interfere with each other.
Options- A. True
- B. False Discuss
Correct Answer: False
Explanation:
PAS use moving coil microphones.- 7. 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.- 8. 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.- 9. 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.- 10. 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.
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