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- Question
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.
- Correct Answer
-
ExplanationThis is Shannon-Hartley theorem.
Communication Systems problems
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- 1. 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 .- 2. 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.- 3. 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.- 4. 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 Discuss
Correct Answer: 512 W
Explanation:
.
- 5. 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.- 6. 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 ?.
- 7. In colour TV receiver, varactor diode is used for
Options- A. detection
- B. rectification
- C. tuning
- D. both (a) and (b) Discuss
Correct Answer: tuning
Explanation:
In varactor diode the applied reverse bias controls the width and therefore capacitance of depletion layer.This capacitance is used for tuning.
- 8. Frequency shift keying is used mostly in
Options- A. telegraphy
- B. telephony
- C. satellite communication
- D. radio transmission Discuss
Correct Answer: telegraphy
Explanation:
Frequency shift keying (FSK) is a system of frequency modulation used in telegraphy.- 9. Which of the following has the highest input impedance?
Options- A. CE
- B. CB
- C. CC
- D. Push pull Discuss
Correct Answer: CC
Explanation:
CC connection has very high input impedance and low output impedance.- 10. Degaussing in a picture tube means
Options- A. Adding magnetism in mask and mounting frame
- B. Removing residual magnetism in mask, shield etc...
- C. Increasing resistance of coils to decrease time constant
- D. Decreasing resistance of coils to increase time constant. Discuss
Correct Answer: Removing residual magnetism in mask, shield etc...
Explanation:
Since gauss is a unit of magnetic flux, degaussing means removal of magnetism.
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