 MCQs in Noise Part I

(Last Updated On: September 10, 2019) This is the Multiples Choice Questions Part 1 of the Series in Noise as one of the Communications Engineering topic. In Preparation for the ECE Board Exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies, Communications Books, Journals and other Communications References.

Online Questions and Answers Topic Outline

• MCQs in External Noise
• MCQs in Phase Noise
• MCQs in Noise Calculation and Measurements
• MCQs in Radio Interference

MCQs in Noise Series

Following is the list of multiple choice questions in this brand new series:

Noise MCQs
PART 1: MCQs from Number 1 – 50                        Answer key: PART I
PART 2: MCQs from Number 51 – 100                   Answer key: PART II
PART 3: MCQs from Number 101 – 150                 Answer key: PART III
PART 4: MCQs from Number 151 – 200                 Answer key: PART IV
PART 5: MCQs from Number 201 – 250                 Answer key: PART V

Start Practice Exam Test Questions Part I of the Series

1. What is the non-continuous noise of irregular pulses or spikes of duration with high amplitudes?

• A. Wander
• B. Jitter
• C. Hits
• D. Singing

2. What theorem sets a limit on the maximum capacity of a channel with a given noise level?

• A. Nyquist theorem
• B. Hartley law
• C. Shannon-Hartley theorem
• D. Shannon theorem

3. Quantizing noise occurs in

• A. PCM
• B. PLM
• C. PDM
• D. PAM

4. Noise always affects the signal in a communications systems at the ________.

• A. transmitter
• B. channel
• C. information source
• D. destination

5. _________ is the random and unpredictable electric signals from natural causes, both internal and external to the system.

• A. Interference
• B. Attenuation
• C. Distortion
• D. Noise

6. Noise from random acoustic or electric noise that has equal energy per cycle over a specified total frequency band.

• A. Gaussian noise
• B. Whiter noise
• C. Thermal noise
• D. All of the above

7. Which causes a quantization noise in PCM system?

• A. Serial transmission errors
• B. The approximation of the quantized signal
• C. The synchronization between encoder and decoder
• D. Binary coding techniques

8. A particular circuit that rids FM of noise

• A. Detector
• B. Discriminator
• C. Phase Shifter
• D. Limiter

9. What is the reference noise temperature in degrees Celsius?

• A. 17
• B. 273
• C. 25
• D. 30

10. Unwanted radio signal on assigned frequency.

• A. Splatter
• B. RFI
• C. Noise
• D. EMI

11. What is the reliable measurement for comparing amplifier noise characteristics?

• A. Thermal agitation noise
• B. Noise factor
• C. Noise margin
• D. Signal-to-noise

12. _________ is measured on a circuit when it is correctly terminated but does not have any traffic.

• A. White noise
• B. Galactic noise
• C. Impulse noise
• D. Atmospheric noise

13. Which standard recommends crosstalk limits?

• A. CCIT G.152
• B. CCIT G.150
• C. CCIT G.151
• D. CCIT G.161

14. Which standard is utilized in intermodulation noise rates on PCM audio channels?

• A. CCIT Rec. G.151
• B. CCIT Rec. G.172
• C. CCIT Rec. G.190
• D. CCIT Rec. G.190

15. What is the reference frequency of CCIT phosphomeric noise measurement?

• A. 800 Hz
• B. 1000 Hz
• C. 1500 Hz
• D. 3400 Hz

16. Reference temperature use in noise analysis

• A. 75 K
• B. 250 K
• C. 290 K
• D. 300 K

17. Which noise is produced by lighting discharges in thunderstorms?

• A. White noise
• B. Extraterrestrial noise
• C. Industrial noise
• D. Atmospheric noise

18. Man-made noise is usually from _______.

• A. transmission over power lines and by ground wave
• B. sky-wave
• C. space-wave
• D. troposphere

19. nif stands for

• A. Non-intrinsic figure
• B. Noise improvement factor
• C. Narrow intermediate frequency
• D. Noise interference figure

20. Industrial noise frequency is between _____.

• A. 0 to 10 KHz
• B. 160 MHz to 200 MHz
• C. 15 to 160 MHz
• D. 200 to 3000 MHz

21. External noise fields are measured in terms of _______.

• A. rms values
• B. dc values
• C. average values
• D. peak values

22. Form of interference caused by rain or dust storms.

• A. Precipitation static
• B. Shot-noise
• C. Galactic noise
• D. Impulse noise

23. At 17˚ C, the noise voltage generated by 5kΩ resistor, operating over a bandwidth of 20KHz is

• A. 1.3 nV
• B. 1.3 µV
• C. 1.3 pV
• D. 1.3 mV

24. ________ is an electric noise produced by thermal agitation of electrons in conductor and semiconductor.

• A. External noise
• B. Internal noise
• C. Thermal noise
• D. Flicker

25. Three identical circuits having 10 dB signal noise-to-noise ratio each are connected in tandem with each other, what is the overall S/N?

• A. 5.23 dB
• B. 14.77dB
• C. 30 dB
• D. 40 dB

26. The noise figure of the first circuit in tandem connection is 10.5 dB while its power gain is 15, what is the over all noise figure if the second circuit has a noise figure of 11 dB?

• A. 11.59 dB
• B. 11.23 dB
• C. 10.79 dB
• D. 10.5 dB

27. Is the interference coming from other communications channels?

• A. Jitter
• B. Crosstalk
• C. RFI
• D. EMI

28. What is the reference noise level?

• A. 10 pW
• B. 0 dBm
• C. 1mW
• D. -90 dBm

29. What is the unit of noise power of psophometer?

• A. pWp
• B. dBa
• C. dBm
• D. dBrn

30. A large emission of hydrogen from the sun that affects communications.

• A. Solar flare
• B. Cosmic disturbance
• C. Ballistic disturbance
• D. Solar noise

31. Atmospheric noise is known as _______noise.

• A. static
• B. cosmic
• C. solar
• D. lunar

32. Standard design reference for environmental noise temperature.

• A. 300 K
• B. 290 K
• C. 32 ˚F
• D. 212˚F

33. Absolute temperature in Kelvin.

• A. ˚C + 273
• B. ˚C + 75
• C. ˚C + 19
• D. ˚C + 290

34. If bandwidth is doubled, the signal power is _________.

• A. not changed
• C. tripled
• D. doubled

35. Name one or more sources of noise bearing on electronic communications.

• A. Steam boiler
• B. Galaxies
• C. Internal combustion engine
• D. Both B and C

36. The transmitter technique adopted to reduce the noise effect of the preceding question is called

• A. noise masking
• B. anitnoise
• C. noise killing
• D. preemphasis

37. Deemphasis in the receiver in effect attenuates modulating signal components and noise in what frequency range?

• A. dc
• B. low
• C. intermediate
• D. high

38. Atmospheric noise or static is not a great problem

• A. at frequencies below 20 MHz
• B. at frequencies below 5 MHz
• C. at frequencies above 30 MHz
• D. at frequencies above 1 MHz

39. What is the proper procedure for suppressing electrical noise in a mobile station?

• A. Apply shielding and filtering where necessary
• B. Insulate a all plain sheet metal surfaces from each other
• C. Apply anti-static spray liberally to all nonmetallic
• D. Install filter capacitors in series with all dc wiring

40. Where is the noise generated that primarily determines the signal-to-noise ratio in a VHF (150MHz) marine-band receiver?

• A. Man-made noise
• B. In the atmosphere
• C. In the receiver front end
• D. In the ionosphere

41. The difference between signal strength at a given point and a reference level is________.

• A. power
• B. dBm
• C. level
• D. ratio

42. Interfering effect of noise, C message weighted, is _________.

• A. dBa
• B. dBm
• C. dBmc
• D. dB

43. F1A weighting refers to ___________.

• A. -90 dBm
• B. dBrnc0
• C. dBrnc
• D. F1A handset

44. Reading a 58 dBrnC on your Western Electric 3A test set at a +7 test point is equal to ______ dBrnc0.

• A. 58
• B. 51
• C. 65
• D. 27

45. Reading a 58 dBrn, at a +7 test point is equal to ________ dBa0.

• A. 26
• B. 65
• C. 51
• D. 46

46. A reading of -50 dBm on the disturbing pair, and -80 on the disturbed pair equals _____ dB of crosstalk coupling.

• A. 20
• B. 30
• C. 60
• D. 25

47. Power is __________.

• A. actual amount of power reference to 1mW
• B. logarithmic ratio of two powers
• C. definite amount of energy per time period
• D. current flow per time period

48. 15 dBa F1A weighted, equals ___________.

• A. -90 dBm
• B. -82 dBm
• C. -85 dBm
• D. -70 dBm

49. You are measuring noise in a voice channel with a Lenkurt 601A, F1A weighting network and a flat meter. Your meter reads -47dBm. What is this reading in dBa?

• A. 77 dBa
• B. 35 dBa
• C. 38 dBa
• D. 32 dBa

50. You are measuring noise at a +3 dB level point, using the Lenkurt 601A, F1A weighting network, and a flat meter. The meter reading is -57dBm. This is ________dBa0.

• A. 20
• B. 15
• C. 25
• D. 17

Complete List of MCQs in Communications Engineering per topic

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