MCQs in Communications Engineering Part 4

This is the Miscellaneous Multiples Choice Questions Part 4 of the Series in Communications Engineering. 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 past Board Questions in Communications Engineering field (Electronics Systems and Technologies). In the actual board, you have to answer 100 items in Electronic Systems and Technologies within 5 hours. You have to get at least 70% to pass the subject. Electronic Systems and Technologies is 30% of the total 100% Board Rating along with Mathematics (20%), General Engineering and Applied Sciences (20%) and Electronics Engineering (30%).

Practice Exam Test Questions

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

Miscellaneous Communications Engineering 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

PART 6: MCQs from Number 251 – 300                 Answer key: PART VI

PART 7: MCQs from Number 301 – 350                 Answer key: PART VII

PART 8: MCQs from Number 351 – 400                 Answer key: PART VIII

PART 9: MCQs from Number 401 – 450                 Answer key: PART IX

PART 10: MCQs from Number 451 – 500                 Answer key: PART X

Continue with Part IV of the Series

Choose the letter of the best answer in each questions.

151. The most common light used in fiber optic link is __

• a. Red
• b. Violet
• c. Infrared
• d. ultraviolet

152. In the telecommunications industry, the most commonly used fiber(s) is/are:

• a. 50 micron
• b. 62.5 micron
• c. 50 and 62.5 micron
• d. 125 micron

153. The abrupt change in refractive index from core to cladding of fiber optic cable is called the:

• a. Total internal reflection
• b. Numerical aperture
• c. Dispersion
• d. Step index

154. A technique that is used to minimize pulse dispersion effect is:

• a. Use a higher frequency light source
• b. Use plastic cladding
• c. Minimize the core diameter
• d. All of the above

155. Light detectors are devices used to sense light energy in fiber optic communication receivers. Which is not an important characteristic of a light detector?

• a. Responsivity
• b. Dark current
• c. Power consumption
• d. Response speed

156. The dispersion of light in fiber-optic cable caused by a portion of the light energy travelling in the cladding is called ___.

• a. Modal dispersion
• b. Material dispersion
• c. Waveguide dispersion
• d. Cable dispersion

157. Which of the following considerations is important when deciding between using a diode laser or an LED?

• a. Response time
• b. Power level
• c. Temperature sensitivity
• d. Failure characteristics

158. The light energy that is always emitted or absorbed in discrete units is called:

• a. Light ray
• b. Boson
• c. Quanta
• d. Light

159. Which of the following Ethernet fiber optic standards uses synchronous, centralized clock?

• a. 10Base-FL (Link)
• b. 10Base-FP (Passive)
• c. 10Base-FB (backbone)
• d. All of the above

160. It is a layer of plastic that surrounds a fiber or group of fiber.

• a. Buffer tube
• b. Bulk head
• c. Cladding
• d. jacket

161. The angular separation between the two half-power points on the power density radiation pattern.

• a. Beamwidth
• b. Bandwidth
• c. Azimuth
• d. Footprint

162. Refers to the direction in space of electric vector of the electromagnetic wave radiated from an antenna and is parallel of the antenna itself.

• a. Propagation
• b. Coordination
• c. Azimuth
• d. Polarization

163. This is often used to cure the problem of great thickness required of lenses used at lower microwave frequencies or for strong curved wavefronts.

• a. Splicing
• b. Zoning
• c. Curving
• d. Polarizing

164. An optic fiber is made of glass with a refractive index of 1.55 and is clad with another glass with a refractive index of 1.51. Launching takes place from air. What numerical aperture does the fiber have?

• a. 0.132
• b. 0.352
• c. 0.032
• d. 0.475

165. For an optical fiber 10 km long with a pulse-spreading constant of 5 ns/km, determine the maximum digital transmission rates for return-to-zero.

• a. 40 Mbps
• b. 30 Mbps
• c. 20 Mbps
• d. 10 Mbps

166. In fiber optics, it is a measure of the conversion efficiency of a photodetector. It is the ratio of the output current of a photodiode to the input optical power and has the unit of amperes per watt.

• a. Responsivity
• b. Dark current
• c. Spectral response
• d. Light sensitivity

167. A phenomenon also called stress corrosion resulting if the glass fiber is exposed to long periods of high humidity.

• a. Scattering loss
• b. Absorption
• c. Dispersion
• d. Static fatigue

168. The theory which states that when visible light or high-frequency electromagnetic radiation illuminates a metallic surface, electrons are emitted.

• a. Photoelectric effect
• b. Planck’s law
• c. Photoemission effect
• d. Rayleigh theory of light

169. The science of measuring only light waves that are visible to the human eye.

• a. Radiometry
• b. Optometry
• c. Optics
• d. Photometry

170. A phenomenon in optical fibers communication system that is caused by the difference in the propagation times of light rays that take different paths down the fiber.

• a. Pulse spreading
• b. Wavelength distortion
• c. Rayleigh scattering
• d. Microbending

171. Determine the fourth Fresnel radius of a microwave link having a transmitter-receiver distance of 50 km, operating at a frequency of 7 GHz. An obstruction is found 15 km from the transmitting station.

• a. 21 meters
• b. 42 meters
• c. 63 meters
• d. 84 meters

172. A radome protecting a microwave transmitting antenna has a relative permittivity of 4, and is designed as a half-wavelength relfectionless slab at operating frequency of 10 GHz. Determine its thickness.

• a. 0.5 cm
• b. 0.75 cm
• c. 0.377 cm
• d. 0.577 cm

173. A satellite transmitter operates at a 6 GHz with a transmitter power of 9 watt and an antenna gain of 45 dBi. The receiver has antenna gain of 30 dBi, and the path length is 35,000 km. calculate the signal strength at the receiver.

• a. -88 dBm
• b. -94 dBm
• c. -84 dBm
• d. -98 dBm

174. Calculate the angle of declination for an antenna using a polar mount at latitude of 75 degrees.

• a. 8.62 deg
• b. 2.61 deg
• c. 4.22 deg
• d. 6.81 deg

175. Telephone communication takes place between two earth stations via satellite 36,000 km apart. Suppose Jim calls Stifler at 8:00 am. Stifler immediately answers back. How much time has elapsed before Jim hears back the beginning of Stifler’s reply, as heard by Stifler?

• a. 0.48 sec
• b. 0.12 sec
• c. 0.36 sec
• d. 0.24 sec

176. A receiving antenna with a gain of 45 dBi looks at a sky with a noise temperature of 28 K. the loss between the antenna and the LNA input, due to the feedhorn, is 0.9 dB, and the LNA has a noise temperature of 40 K. calculate G/T.

• a. 23.42 dB
• b. 20.62 dB
• c. 26.02 dB
• d. 28.51 dB

177. What is the gain of a pyramidal horn in dB, with width and height of 15 cm and 12 cm, respectively with an operating frequency of 11.7 GHz.

• a. 172.02 dB
• b. 44.7 dB
• c. 22.35 dB
• d. 19.25 dB

178. A wide area blackout of HF radio communication as well as loss of radio contact for about an hour on the sunlit side of earth.

• a. R1
• b. R2
• c. R3
• d. R4

179. Irises are metallic plates used to match waveguide impedances. When irises are placed along the walls of a waveguide it acts as __.

• a. Capacitive
• b. Inductive
• c. LC resonant circuit
• d. Both B and C

180. A single-mode fiber is made with core diameter of 12 micrometers and is coupled to a light source with a wavelength of 1.40 micrometers. Its core glass has a refractive index of 1.55. Determine the cladding index required for producing single-mode propagation.

• a. 1.547
• b. 2.394
• c. 1.475
• d. 2.439

181. Radio waves were first predicted mathematically by:

• a. Armstrong
• b. Hertz
• c. Maxwell
• d. Marconi

182. The power per transponder of a typical Ku-band satellite is in the range:

• a. 5 to 25 watts
• b. 50 to 250 watts
• c. 500 to 2500 watts
• d. Depends on its orbit

183. The loss in single-mode fiber-optic cable due to a splice is about:

• a. 0.02 dB
• b. 0.2 dB
• c. 1 dB
• d. 3 dB

184. An exclusive meteorological satellite launched by Indian Satellite system. It is located at 74 degree East longitude.

• a. KALPANA-1
• b. INSAT-2E
• c. EDUSAT
• d. SHIVA

185. If light leaves a material of refractive index 1.75 and crosses an abrupt boundary into a material of refractive index 1.20, the fresnel loss would be:

• a. 0.346 dB
• b. 0.149 dB
• c. 0.613 dB
• d. 0.153 dB

186. A white fiber with a black tracer is most likely to be fiber number:

• a. 18
• b. 16
• c. 12
• d. 14

187. The temperature range for fiber operation, range typically

• a. 0 to 60 degree Celsius
• b. -30 to +70 degree Celsius
• c. -40 to +80 degree Celsius
• d. -100 to +100 degree Celsius

188. A disadvantage of microstrip compared with stripline is that microstrip:

• a. Does not readily lend itself to printed circuit techniques
• b. Is more likely to radiate
• c. Is bulkier
• d. Is more expensive and complex to manufacture

189. In fiber optics, the SONET channel with capacity sending up to 40 Gbps.

• a. OC-48
• b. OC-768
• c. OC-214
• d. OC-1

190. The orbital inclination of ISS is:

• a. 56.1 degrees
• b. 65.1 degrees
• c. 61.5 degrees
• d. 51.6 degrees

191. The process of adjusting the orbit of a geostationary satellite so that it appears to remain stationary above a point on earth.

• a. Station keeping
• b. Station hunting
• c. Station kicking
• d. None of the above

192. A typical value for the spectral width of a laser is:

• a. 1310 nm
• b. 850 nm
• c. 3 nm
• d. 62.5 nm

193. A range of microwave frequencies more easily passed by the atmosphere than the others is called a ___

• a. Window
• b. Critical frequency
• c. Gyro frequency range
• d. Resonance in the atmosphere

194. An acronym for short range navigation, a type of electronic navigation and bombing system with a precision radar beacon used in the B-26 and B-29 bomber aircraft during the Korean war.

• a. LORAN
• b. LORAN D
• c. SHORAN
• d. SHORAN D

195. The bending radius during installation for a lightweight fiber cable.

• a. 70 mm
• b. 175 mm
• c. 350 mm
• d. 500 mm

196. In radio navigation, what is known in Russia as the counterpart of the LORAN-C US navigation system?

• a. Omega
• b. Chayka
• c. Alpha
• d. Decca

197. What is the effective earth’s radius when Ns=300?

• a. 8500 km
• b. 6370 km
• c. 7270km
• d. 7950 km

198. The TWT is sometimes preferred to the multicavity klystron amplifier because it

• a. Is more efficient
• b. Has a greater bandwidth
• c. Has a higher number of modes
• d. Produces a higher output power

199. A ray of light in a transparent material of refractive index 1.5 is approaching a material with a refractive index of 1.48. At the boundary, the critical angle is:

• a. 90 degrees
• b. 9.4 degrees
• c. 75.2 degrees
• d. 80.6 degrees

200. In fusion splicing of the fibers, the arc that occurs between the two electrodes is about ___ with an adjustable current up to ___.

• a. 7,000 volts 25 mA
• b. 10,000 volts 125 mA
• c. 1,000 volts 251 mA
• 70,000 125 mA

Complete List of MCQs in Communications Engineering per topic

Series of Multiple Choice Questions in Electronics Systems and Technologies

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