Communication Systems problems
- 1. The velocity of sound waves in air
Options- A. is constant at all temperatures
- B. varies directly as temperature
- C. varies inversely as absolute temperature
- D. varies directly as square root of absolute temperature Discuss
Correct Answer: varies directly as square root of absolute temperature
Explanation:
v ? T.
- 2. 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.
- 3. 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.
- 4. A carrier wave carries information.
Options- A. True
- B. False Discuss
Correct Answer: False
Explanation:
Carrier does not have any information.
- 5. 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.
- 6. 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.
- 7. 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:
.
- 8. 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.
- 9. 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.
- 10. 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 .
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