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- Question
A 400 W carrier is amplitude modulated with m = 0.75. The total power in AM is
Options- A. 400 W
- B. 512 W
- C. 588 W
- D. 650 W
- Correct Answer
- 512 W
Explanation
.
Communication Systems problems
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- 1. A generator is feeding power to a transmission line of characteristic impedance Z0. The line is terminated in impedance ZL. Standing waves will be set up if
Options- A. ZL = Z0
- B. ZL < Z0
- C. ZL > Z0
- D. both (b) and (c) Discuss
Correct Answer: both (b) and (c)
Explanation:
Both the case, i.e., ZL > Z0 and ZL < Z0 give rise to standing waves.- 2. A woofer should be fed from the input through a
Options- A. low pass filter
- B. high pass filter
- C. band pass filter
- D. band stop filter Discuss
Correct Answer: low pass filter
Explanation:
Woofer is a low frequency loud speaker covering the range 16 Hz to 500 Hz.- 3. A carrier wave carries information.
Options- A. True
- B. False Discuss
Correct Answer: False
Explanation:
Carrier does not have any information.- 4. A modem is classified as low speed if data rate handled is
Options- A. upto 100 bps
- B. upto 250 bps
- C. upto 400 bps
- D. upto 600 bps Discuss
Correct Answer: upto 600 bps
Explanation:
When data rate in bits per second is upto 600, modem is low speed.- 5. Counterpoise is used in coils having
Options- A. high resistivity
- B. low resistivity
- C. medium resistivity
- D. both (b) and (c) Discuss
Correct Answer: high resistivity
Explanation:
Counterpoise is a horizontally buried wire used to provide low grounding resistance in high resistivity soils.- 6. In sound recording the degree of pre-emphasis is about 6 dB/ octave.
Options- A. True
- B. False Discuss
Correct Answer: False
Explanation:
It erases the matter already existing on the tape.- 7. Tracking of extra terrestrial objects requires
Options- A. high transmitting power
- B. very sensitive receiver
- C. fully steerable antenna
- D. all of the above Discuss
Correct Answer: all of the above
Explanation:
All the three are required.- 8. 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?
Options- A. 1002 kHz
- B. 1000 kHz
- C. 999.2 kHz
- D. 998.0 kHz Discuss
Correct Answer: 1000 kHz
Explanation:
Frequency present in the sidebands is equal to = fc ± fm, fc ± 2fm , fc ± 3fm .- 9. If C is capacity of noisy channel, (bits/s), ?f is bandwidth Hz and S/N is signal to noise ratio, then
Options- A.
- B.
- C.
- D.
Discuss
Correct Answer:
Explanation:
This is Shannon-Hartley theorem.- 10. Which of the following cannot be the Fourier series expansion of a periodic signal?
Options- A. x(t) = 2 cos t + 3 cos 3t
- B. x(t) = 2 cos pt + 7 cos t
- C. x(t) = cos t + 0.5
- D. x(t) = 2 cos 1.5pt + sin 3.5 pt Discuss
Correct Answer: x(t) = cos t + 0.5
Explanation:
x(t) = cos t + 0.5not satisfies the Dirichlet condition.
The integration of constant term is ?.
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