# MCQs in Noise Part V

Compiled MCQs in Noise Part 5 of the series as one topic in Electronic System and Technologies (Communications Engineering) in the ECE Board Exam.

This is the Multiples Choice Questions Part 5 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 decibel (dB)

### 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

### Continue Practice Exam Test Questions Part V of the Series

201. A power level of 50 ÂµW could be expressed as:

• a. 1.39 dBm
• b. -4.3 dBm
• c. 1 dBm
• d. -13 dBm

202. If a power of 0.25 mW is launched into a fiber system with an overall loss of 15 dB the output power would be:

• a. 250 Âµ/W
• b. 31.6 ÂµW
• c. 7.9 ÂµW
• d. 15 dBm

203. A system having an input power of 2 mW an output power of 0.8mW has a loss of:

• a. 2.98 dBm
• b. 3.98 dB
• c. 3.98 ÂµW
• d. 1.98 mW

204. An output of -10 dB means that the power has been

• a. Halved in value
• b. Increased by a factor of 10
• c. Reduced by a factor of 10
• d. Doubled

205. Any unwanted form of energy interfering the reception of wanted signal is called

• a. Noise
• b. Sideband
• c. Harmonics
• d. Modulation

206. Is the reduction of signal amplitude as it passed over the transmission medium.

• a. Noise
• b. Distortion
• c. Attenuation
• d. Interference

207. Signal waveform perturbation or deviation caused by imperfect response of the system to the desired signal

• a. Noise
• b. Aliasing
• c. Distortion
• d. Interference

208. Signal attenuation can be corrected by

• a. Filtering
• b. Modulation
• c. Equalization
• d. Amplification

209. Distortion in a waveform can be corrected by

• a. Filtering
• b. Modulation
• c. Equalization
• d. Amplification

210. Signal contamination by extraneous or external sources, such as, other transmitters, power lines, and machinery.

• a. Noise
• b. Distortion
• c. Harmonics
• d. Interference

211. Man-made or industrial noise is also known as

• a. Noise
• b. Distortion
• c. Interference
• d. Thermal Noise

212. The noise performance of a receiver or circuit. It is expressed as ratio of the S/N power at the output.

• a. Noise figure
• b. S/N ratio
• c. Signal figure
• d. Figure of merit

213. Noise that is caused by natural disturbances such as lightning discharge.

• a. Static noise
• b. Space noise
• c. Atmospheric noise
• d. A or C

214. Atmospheric or static noise becomes less severe at frequencies

• a. Below 30 KHz
• b. Between 30 KHz and 300 KHz
• c. Between 300 KHz and 30 MHz
• d. Above 30 MHz

215. Considered as space noise or extraterrestrial noise

• a. Solar noise
• b. Cosmic noise
• c. Black-body noise
• d. All of the above

216. Which statement is true

• a. Industrial noise is usually of impulse type
• b. Distant stars produce atmospheric noise
• c. Active switches are sources of man-made noise
• d. Static noise is due to lightning discharges and other natural electric disturbances occurring in the atmosphere.

217. Noise performance of microwave system is usually expressed in terms of

• a. Noise voltage, Vn = √4KTBR
• b. Noise power, Pn = KTB
• c. Noise temperature, Te = (F – 1)290
• d. Noise figure, F = (S/N)I / (S/N)o

218. Which circuit contributes most to the noise at the receiver?

• a. RF amplifier
• b. Mixer
• c. Detector
• d. Local Oscillator

219. Which noise figure represents the lowest noise?

• a. 1.5 dB
• b. 2.0 dB
• c. 3.7 dB
• d. 4.1 dB

220. Denote the interference of noise in dB above an adjusted reference noise. The adjusted reference noise level was a 1 kHz tone, set at -85 dBm

• a. dBa
• b. dBm
• c. dBa0
• d. pWp

221. The extent of noise referred to a test tone level of zero dBm.

• a. dBa
• b. dBm
• c. dBa0
• d. pWp

222. An amplifier operating over a 4 MHz bandwidth has a 100 â„¦ input resistance and is operating at 300°K. Determine the noise power generated.

• a. 1.656 x 10-14 Watts
• b. 1656 nW
• c. 1.656 pW
• d. 1.656 uW

223. Generally used when noise readings are measured using the C-message weighting network. The reference level was 1 kHz tone, set at -90 dBm

• a. dBa
• b. dBm
• c. dBaO
• d. dBmC

224. The measurement of noise was made with a C-message filter, and the reading is taken at a test point where the level is zero dBm.

• a. dBaO
• b. dBmCo
• c. dBa
• d. dBmC

225. Which of the following is not an important cause of distortion in DC signaling

• a. line resistance
• b. line inductance
• c. line capacitance
• d. all of the above

226. There are a number of different sources of radio noise, the most important being

• a. Galactic noise
• c. Atmospheric noise
• d. All of the above

227. The amount of noise power is measured using a psophometric weighting network. This unit of measurement is generally used in Europe where the standard reference tone is 800 hertz, 1 picowatt.

• a. dBa
• b. dBm
• c. dBaO
• d. pWp

228. Noise produced mostly by lightning discharges in thunderstorms.

• a. White noise
• b. Industrial noise
• c. Atmospheric noise
• d. Extraterrestrial noise

229. Propagation of man made noise is chiefly by

• a. Transmission over power lines and by ground wave
• b. Space wave
• c. Sky wave
• d. None of these

230. A more precise evaluation of the quality of a receiver as far as noise is concerned

• a. S/N
• b. VSWR
• c. Noise factor
• d. Noise margin

231. NIF stands for

• a. Non-intrinsic figure
• b. Noise interference figure
• c. Noise improvement factor
• d. Narrow intermediate frequency

232. External noise fields are measured in terms of

• a. Dc values
• b. Rms values
• c. Peak values
• d. Average values

233. Form of interference caused by rain, hail, snow or dust storms

• a. Shot noise
• b. Galactic noise
• c. Impulse noise
• d. Precipitation static

234. Extra-terrestrial noise is observable at frequencies from

• a. 0 to 20 KHz
• b. 8 MHz to 1.43 GHz
• c. 5 to 8 GHz
• d. 15 to 160 MHz

235. Industrial noise is observable from

• a. 15 to 160 MHz
• b. 200 to 3000 MHz
• c. 0 to 10 kHz
• d. 8 Mhz to 1.43 GHz

236. Noise that becomes significant at VHF range and above

• a. Atmospheric
• b. Transit-time
• c. Galactic
• d. White

237. Noise figure for an amplifier with noise is always

• a. 0 dB
• b. Infinite
• c. Less than 1
• d. Greater than 1

238. The noise generated by the tube, transistor or integrated circuit in an amplifier.

• a. White noise
• b. Amplification noise
• c. Active noise
• d. Dynamic Noise

239. Electrical noise inherent to a particular device, circuit or system that remains when no other signal is present.

• a. Shot noise
• b. Thermal noise
• c. Background noise
• d. Static noise

240. A wideband form of impulse noise generated by the electric arc in the spark plugs of an internal combustion engine. This noise is a common problem in mobile radio system.

• a. Thermal noise
• b. Shot noise
• c. Amplification noise
• d. Ignition noise

241. The amount of power in dB referred to one Kilowatt

• a. dBW
• b. dBk
• c. dBm
• d. Dbv

242. Noise in any form of electromagnetic interference that can be traced to non-natural causes.

• b. Distortion
• c. External noise
• d. Internal noise

243. The frequency range wherein noise is said to be intense.

• a. Noise equivalent bandwidth
• b. Spectral response
• c. Cut-off frequency
• d. Noise cut-off frequency

244. Refers to the temperature that corresponds to the spectral energy distribution of a noise.

• a. Absolute temperature
• b. Temperature band
• c. Noise-equivalent temperature
• d. Critical temperature

245. A passive circuit, usually consisting of capacitance and/or inductance, that I inserted in series with the a-c power cord of an electronic device which will allow the 60-Hz current to pass and suppressed high frequency noise components.

• a. Noise filter
• b. Noise limiter
• c. Noise floor
• d. Noise quieting

246. What do you call the level of background noise, relative to some reference signal.

• a. Noise figure
• b. Minimum noise
• c. Reference noise
• d. Noise floor

247. A circuit often used in radio receivers that prevents externally generated noise from exceeding amplitude. They are also called noise clippers

• a. Noise floor
• b. Noise filter
• c. Noise limiter
• d. Noise clamper

248. It is referred to as a short burst of electromagnetic energy.

• a. Pulse
• b. Noise pulse
• c. Spike
• d. Noise floor

249. The reduction of internal noise level in a frequency-modulated (FM) receiver as a result of an incoming signal.

• a. Noise quieting
• b. Noise limiting
• c. Noise suppression

250. Noise generated within electronic equipment by either passive or active components.

• a. Shot noise
• b. Thermal noise
• c. Circuit noise
• d. External noise

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

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