# MCQ in Noise Part 1 | ECE Board Exam

(Last Updated On: January 26, 2024)

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.

#### MCQ Topic Outline included in ECE Board Exam Syllabi

• MCQ in External Noise
• MCQ in Phase Noise
• MCQ in Noise Calculation and Measurements

#### Start Practice Exam Test Questions Part 1 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

Explanation:

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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

Explanation:

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3. Quantizing noise occurs in

A. PCM

B. PLM

C. PDM

D. PAM

Explanation:

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

A. transmitter

B. channel

C. information source

D. destination

Explanation:

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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

Explanation:

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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

Explanation:

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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

Explanation:

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8. A particular circuit that rids FM of noise

A. Detector

B. Discriminator

C. Phase Shifter

D. Limiter

Explanation:

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

A. 17

B. 273

C. 25

D. 30

Explanation:

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10. Unwanted radio signal on assigned frequency.

A. Splatter

B. RFI

C. Noise

D. EMI

Explanation:

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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

Explanation:

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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

Explanation:

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13. Which standard recommends crosstalk limits?

A. CCIT G.152

B. CCIT G.150

C. CCIT G.151

D. CCIT G.161

Solution:

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

Solution:

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

A. 800 Hz

B. 1000 Hz

C. 1500 Hz

D. 3400 Hz

Solution:

16. Reference temperature use in noise analysis

A. 75K

B. 250K

C. 290K

D. 300K

Explanation:

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

A. White noise

B. Extraterrestrial noise

C. Industrial noise

D. Atmospheric noise

Explanation:

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18. Man-made noise is usually from _______.

A. transmission over power lines and by ground wave

B. sky-wave

C. space-wave

D. troposphere

Explanation:

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19. nif stands for

A. Non-intrinsic figure

B. Noise improvement factor

C. Narrow intermediate frequency

D. Noise interference figure

Solution:

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

Explanation:

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

A. rms values

B. dc values

C. average values

D. peak values

Solution:

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

A. Precipitation static

B. Shot-noise

C. Galactic noise

D. Impulse noise

Explanation:

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

Explanation:

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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. 14.77 dB

C. 30 dB

D. 40 dB

Solution:

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

Solution: What is the over all noise figure

Solution:

27. Is the interference coming from other communications channels?

A. Jitter

B. Crosstalk

C. RFI

D. EMI

Explanation:

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28. What is the reference noise level?

A. 10 pW

B. 0 dBm

C. 1mW

D. -90 dBm

Explanation:

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

A. pWp

B. dBa

C. dBm

D. dBrn

Solution:

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

A. Solar flare

B. Cosmic disturbance

C. Ballistic disturbance

D. Solar noise

Explanation:

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31. Atmospheric noise is known as _______noise.

A. static

B. cosmic

C. solar

D. lunar

Explanation:

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32. Standard design reference for environmental noise temperature.

A. 300K

B. 290K

C. 32˚F

D. 212˚F

Explanation:

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33. Absolute temperature in Kelvin.

A. ˚C + 273

B. ˚C + 75

C. ˚C + 19

D. ˚C + 290

Explanation:

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

A. not changed

C. tripled

D. doubled

Solution:

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

Explanation:

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

B. anitnoise

C. noise killing

D. preemphasis

Explanation:

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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

Explanation:

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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

Solution:

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

Explanation:

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

B. In the atmosphere

C. In the receiver front end

D. In the ionosphere

Explanation:

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

A. power

B. dBm

C. level

D. ratio

Explanation:

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

A. dBa

B. dBm

C. dBmc

D. dB

Explanation:

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43. F1A weighting refers to ___________.

A. -90 dBm

B. dBrnc0

C. dBrnc

D. F1A handset

Explanation:

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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

Explanation:

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48. 15 dBa F1A weighted, equals ___________.

A. -90 dBm

B. -82 dBm

C. -85 dBm

D. -70 dBm

Solution:

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

A. 77 dBa

B. 35 dBa

C. 38 dBa

D. 32 dBa

Solution:

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 -57 dBm. This is ________dBa0.

A. 20

B. 15

C. 25

D. 17

Solution:

#### Questions and Answers in Noise Series

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

MCQ in Noise
PART 1: MCQ from Number 1 – 50                        Answer key: PART 1
PART 2: MCQ from Number 51 – 100                   Answer key: PART 2
PART 3: MCQ from Number 101 – 150                 Answer key: PART 3
PART 4: MCQ from Number 151 – 200                 Answer key: PART 4
PART 5: MCQ from Number 201 – 250                 Answer key: PART 5

### Complete List of MCQ in Communications Engineering per topic

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