 MCQs in Transmission Fundamentals Part IV

(Last Updated On: September 10, 2019) This is the Multiples Choice Questions Part 4 of the Series in Transmission Fundamentals 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 Transmission System
• MCQs in Transmission Medium
• MCQs in Velocity and Line Wavelength
• MCQs in Characteristics Impedance
• MCQs in Primary Line Constants and Propagation Constants
• MCQs in Standing Waves
• MCQs in Voltage Standing Wave Ratio
• MCQs in Telephone Lines and Cables
• MCQs in Wave Guides
• MCQs in Balanced and Unbalanced Lines
• MCQs in Twisted pair wire, Coaxial Cable
• MCQs in Decibel
• MCQs in Signal and Noise Fundamentals

MCQs in Transmission Fundamentals Series

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

Transmission Fundamentals 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 Practice Exam Test Questions Part IV of the Series

151. One Neper (Np) is how many decibels?

• a. 8.866
• b. 8.686
• c. 8.688
• d. 8.868

152. A signal is amplified 100 times in power. The dB gain is

• a. 20 dB
• b. 119 dB
• c. 15 dB
• d. 25 dB

153. Which of the following is used to measure SWR?

• a. Spectrum analyzer
• b. Reflectometer
• c. Oscilloscope
• d. Multimeter

154. 214-056 twin lead which is commonly used for TV lead-in has a characteristic impedance of

• a. 52 ohms
• b. 75 ohms
• c. 600 ohms
• d. 300 ohms

155. What is the characteristic impedance of a transmission line which is to act a s a quarterwave matching transformer between a 175 ohms transmission line and 600 ohms load?

• a. 300.04 ohms
• b. 324.04 ohms
• c. 310.04 ohms
• d. 320.04 ohms

156. What is the EIRP in dBW of a 50dB antenna connected to a transmitter with an output of 10kW through a transmission line with loss of 5dB?

• a. 85 dBW
• b. 955 dBW
• c. 90 dBW
• d. 80 dBW

157. A coaxial cable is a good example of a/an

• a. Unbounded medium
• b. Transmission channel
• c. Non-metallic medium
• d. Bounded medium

158. If a quarterwave transformer is required to match a 180 ohm load to a transmission line with and impedance of 300 ohms, what should be the characteristic impedance of the matching ransformer? Assume that the matching transformer is to be connected directly to the load.

• a. 180 ohms
• b. 232 ohms
• c. 300 ohms
• d. 480 ohms

159. A transmitter of 100W RF power output, 100% modulated is operating on a frequency of 169MHz. The antenna transmission line consists of a 50 ohms coaxial cable 150ft long. The coaxial inner conductor outer diameter is 0.162in. determine the outside diameter of the outer conductor if the outer conductor has a thickness of 0.05 in(assume K=1).

• a. 1.0 in
• b. 0.9 in
• c. 0.7 in
• d. 0.5 in

160. In the preceding problem , calculate the line current.

• a. 1.7A
• b. 1.3A
• c. 1.5A
• d. 1.0A

161. Determine also the total attenuation of the line in the preceding problem.

• a. 2.0dB
• b. 1.5 dB
• c. 2.5 dB
• d. 1.0 dB

162. What is the maximum subscriber loop length, in ft, of a telephone system if the signaling resistance is 1800ohms using a telephone cable pair of gauge #26 with loop resistance of 83.5 ohms per 100ft. Assume the telephone set resistance is equal to 200 ohms.

• a. 15,161.7 feet
• b. 19,161 feet
• c. 15,300 feet
• d. 20,000 feet

163. If the same subscriber loop above limits the voice attenuation to a maximum of 6dB, what is the maximum allowable subscriber loop length, in feet, using the same gauge #26 telephone wire? Assume a 2.7dB loss per mile.

• a. 20,000 ft
• b. 13,900 ft
• c. 15,280 ft
• d. 11,733 ft

164. The input is 0.1W and the network gain is 13dB, the output is

• a. 2.0 W
• b. 2.5 W
• c. 1.5 W
• d. 1.8 W

165. Known as one-tenth of a neper.

• a. dB
• b. dBm
• c. dBp
• d. dNp

166. the input impedance of a quarterwave short-circuited transmission line at its resonant frequency is

• a. 0 ohms
• b. Infinite or an open circuit
• c. Ohm
• d. 70 ohms

167. The ratio of the largest rms value to the smallest rms value of the voltage in the line is called

• a. SWR
• b. ISWR
• c. VSWR
• d. Coefficient of reflection

168. An open-wire, two-wire transmission line is to be connected to a dipole antenna through a quarter-wave matching stub. At a frequency of 10 MHz, compute the length of the dipole

• a. 20 meters
• b. 7.5 meters
• c. 15 meters
• d. 25 meters

169. From the preceding problem, compute also the length of the quarterwave stub.

• a. 15 meters
• b. 7.5 meters
• c. 20 meters
• d. 25 meters

170. To find the characteristic impedance of a coaxial cable, measurements are made with (a) the far end open circuited and (b) far end short circuited, the corresponding readings being a) Ro=3ohms and Xc=55 ohms, capacitive b) RS = 10 ohms and XL = 90 ohms, inductive. What is the characteristic impedance Zo of the line?

• a. 75.7 – j2.0 ohms
• b. 70.7 + j1.19 ohms
• c. 87.5 – j5 ohms
• d. 70.7 – j1.97 ohms

171. A TV antenna receives a signal measured at 200mV and is immediately amplified by a preamplifier with a 15dB gain. This amplified signal then passes through a coaxial cable with 3dB loss, what is the resulting input to the TV set, in dBmV?

• a. 1.98
• b. 13.98
• c. -1.98
• d. -13.98

172. The characteristic impedance of a transmission line does not depend upon its___________.

• a. Conductor spacing
• b. Conductor diameter
• c. Length
• d. Conductor radius

173. What does a power difference of -3dB mean?

• a. A loss of one third of the power
• b. A loss of one half of the power
• c. A loss of three watts of power
• d. No significant change

174. Which of the following is an advantage of the balance transmission line?

• a. Easy installation
• b. Outer shield eliminates radiation losses
• c. Low attenuation
• d. None of these

175. Waveguides are used mainly for microwave transmission because

• a. They are bulky at lower frequencies
• b. Losses are heavy at lower frequencies
• c. They depend on straight line propagation
• d. No generators are powerful enough to excite them

176. The input is 1W and the network loss is 27dB, the output is

• a. 1 mW
• b. 3 mW
• c. 2 mW
• d. 4 mW

177. A combiner has two inputs +30dBm and +30dBm, what is the resultant output?

• a. +36 dBm
• b. +30 dBm
• c. +60 dBm
• d. +33 dBm

178. The ratio of the smallest to the largest rms current value is called

• a. SWR
• b. VSWR
• c. ISWR
• d. Coefficient of reflection

179. If the ratio of the maximum current to minimum current in a transmission line is 2:1 then the ratio of the maximum voltage to minimum voltage is

• a. 4:1
• b. 1:2
• c. 1:4
• d. 2:1

180. Two wires of 600 ohms characteristic impedance is to be constructed out of a number 12 wire (81 mils). Find the attenuation of the line at 0.6GHz per 100feet length

• a. 0.05 dB
• b. 0.55 dB
• c. 0.44 dB
• d. 0.35 dB

181. In the preceding problem, determine the spacing between wires from center to center.

• a. 6 in
• b. 4 in
• c. 5 in
• d. 3 in

182. A lossless transmission line has a shunt capacitance of 100nF/m and a series inductance of 4mH/m. What is the characteristic impedance?

• a. 500 ohms
• b. 400ohms
• c. 300 ohms
• d. 200 ohms

183. A ten times power change in transmission system is equivalent to

• a. 10 dBm
• b. 1 dB
• c. 20 dB
• d. 100 dB

184. A type of transmission line employed where balanced properties are required.

• a. Balun
• b. Parallel-wire line
• c. Coaxial line
• d. Quarterwave line

185. What is the characteristic impedance of a transmission line which has a capacitance of 40nF/ft and an inductance of 0.5mH/ft

• a. 111.8 ohms
• b. 110.8 ohms
• c. 112.8 ohms
• d. 109.8 ohms

186. The input power to a loss-free cable is 5W. If the reflected power is 7dB down on the incident power, the output power to the load is

• a. 4 W
• b. 5 W
• c. 6 W
• d. 7 W

187. To be properly matched the ratio of a maximum voltage along a transmission line should be equal to

• a. 1
• b. 10
• c. 50
• d. 2

188. A coaxial line with an outer diameter of 6mm has a 50 ohms characteristic impedance. If the dielectric constant of the insulation is 1.60., calculate the inner diameter.

• a. 2.09 cm
• b. 2.09 in
• c. 2.09 mm
• d. 2.09 mm

189. If an amplifier has equal input and out impedance, what voltage ratio does the gain of 50dB represent?

• a. 316.2
• b. 325.2
• c. 320.1
• d. 315.0

190. What is the inductance per foot of a cable that has a capacitance of 50 pF/ft and a characteristic impedance of 60 ohms?

• a. 0.167uH/ft
• b. 0.178 uH/ft
• c. 0.19 uH/ft
• d. 0.18 uH/ft

191. The ratio between the energy absorbed by a surface to the total energy received by the surface.

• a. Reflection coefficient
• b. Absorption coefficient
• c. Linear coefficient
• d. Thermal coefficient

192. When the diameter of the conductors of a wire transmission line is held constant, the effect of decreasing the distance between the conductors is

• a. Increase the surge impedance
• b. Increase the radiation resistance
• c. Decrease the SWR
• d. Decrease the impedance

193. The higher the gauge number if a conductor

• a. The bigger the diameter
• b. The higher the resistance or the smaller the diameter
• c. The higher the resistance
• d. None of the above

194. A short length transmission line used to reduce/eliminate standing waves in the main transmission line.

• a. Stub
• b. Balun
• c. λ/4 transformer
• d. slot

195. ratio of reflected power to incident power?

• a. Incidence
• b. Reflectance
• c. Reflection index
• d. None of these

196. A quarter wave transformer is used to match a 600 ohms lad antenna to a ling of 52 ohms impedance, the characteristic impedance of the matching transformer is

• a. 200 ohms
• b. 150 ohms
• c. 176 ohms
• d. 300 ohms

197. What is the capacitance of 55 miles #44 copper wire spaced 18 inches? From wire tables, #44 wire has a radius to 0.10215 in.

• a. 0.476 uF
• b. 0.476 nF
• c. 0.476 pF
• d. 0.476 fF

198. A two-transmission line consists of No. 12 wire AWG (81mils). The distance between wire centers is 10 inches. What is the characteristic impedance of the line?

• a. 650 ohms
• b. 300 ohms
• c. 600 ohms
• d. 660 ohms

199. In the preceding problem, what is the attenuation in dB per 100ft of the line for a frequency of 4 MHz?

• a. 0.05
• b. 0.03
• c. 0.04
• d. 0.06

200. What is the SWR when a transmission line is terminated in a short circuit?

• a. Zero
• b. One
• c. Infinite
• d. indeterminate

Complete List of MCQs in Communications Engineering per topic

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