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- Question
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
- Correct Answer
- varies directly as square root of absolute temperature
Explanationv ? T.
Communication Systems problems
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- 1. As the frequency increases, the absorption of ground wave by earth's surface
Options- A. decreases
- B. increases
- C. remains the same
- D. either (a) or (c) Discuss
Correct Answer: increases
Explanation:
Because of this reason ground waves can be used for frequencies upto about 1600 kHz only.- 2. The colour subcarrier and sidebands produced by its modulation with the chrominance signals are accommodated in the standard channel width by the process of
Options- A. frequency adjustment
- B. frequency interleaving
- C. frequency changing
- D. frequency amalgamation Discuss
Correct Answer: frequency interleaving
Explanation:
In frequency interleaving the space between bundles is used for colour signal.- 3. Consider the following statements
- The amplitude of an FM wave is constant
- FM is more immune to noise than AM
- FM broadcasts operate in upper VHF and UHF frequency ranges
- FM transmitting and receiving equipments are simpler as compared to AM transmitting and receiving equipments
Options- A. 1, 2, 3, 4
- B. 1, 2, 3
- C. 2, 3, 4
- D. 1, 3, 4 Discuss
Correct Answer: 1, 2, 3
Explanation:
FM equipments are complex as compared to AM equipments.- 4. Some types of traps used in video IF amplifier of colour TV are
Options- A. shunt traps
- B. series traps
- C. absorption traps
- D. all of the above Discuss
Correct Answer: all of the above
Explanation:
All these are used.- 5. Signal to noise ratio of microphone is defined as the ratio of output when the sound pressure is __________ to the output in the absence of any sound signal.
Options- A. 0.5 Pa
- B. 0.2 Pa
- C. 0.1 Pa
- D. 0.01 Pa Discuss
Correct Answer: 0.1 Pa
Explanation:
0.1 Pa (= 0.5 x 10-4 W/m2) is taken as standard sound pressure for defining S/N ratio of microphones.- 6. 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.- 7. 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.- 8. A carrier wave carries information.
Options- A. True
- B. False Discuss
Correct Answer: False
Explanation:
Carrier does not have any information.- 9. 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.- 10. 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.
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