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# MCQ in Transmission Fundamentals Part 5 | ECE Board Exam

This is the Multiple Choice Questions Part 5 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.

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

• MCQ in Transmission System
• MCQ in Transmission Medium
• MCQ in Velocity and Line Wavelength
• MCQ in Characteristics Impedance
• MCQ in Primary Line Constants and Propagation Constants
• MCQ in Standing Waves
• MCQ in Voltage Standing Wave Ratio
• MCQ in Telephone Lines and Cables
• MCQ in Wave Guides
• MCQ in Balanced and Unbalanced Lines
• MCQ in Twisted pair wire, Coaxial Cable
• MCQ in Decibel
• MCQ in Signal and Noise Fundamentals

#### Continue Practice Exam Test Questions Part 5 of the Series

Choose the letter of the best answer in each questions.

201. If the 10% of the microwave power is reflected at the mismatch, find the return loss.

a. 0.1 dB

b. 10 dBm

c. -10 dB

d. -10 dBm

Solution:

202. If the return loss is 20 dB, find the present reflected power.

a. 1%

b. 10%

c. 5%

d. 20%

Solution:

203. Convert โten times biggerโ to the equivalent numerical dB

a. 20 dB

b. 15 dB

c. 5 dB

d. 10 dB

Solution:

204. Convert โone-half as largeโ to equivalent numerical dB

a. 3 dB

b. -3 dB

c. 2 dB

d. -2 dB

Solution:

205. Special semiconductor diode use for electronically adjustable attenuation

a. Ideal diode

b. PIN diode

c. Zener diode

d. Tunel diode

Solution:

206. A 50 ohm line is probed and found to have a SWR of 2.6, what are the two possible quarter wave transformers sizes that may be used to match the load to the line of the transformer are properly positioned.

a. 22 ohm, 82 ohm

b. 31 ohm, 80.5 ohm

c. 26.2 ohm, 12.71 ohm

d. 12.32 ohm, 26.7 ohm

Solution:

207. A balanced load of 900 ohm pure resistance is fed through a balanced 600 ohm transmission line which is 90 electrical degree long. The balanced 600 ohm transmission line is in turn fed from a 50 ohm coaxial line by means of a half-wave balancing section. What is the standing wave ratio on the 600 ohm line?

a. 1.0

b. 2.5

c. 1.5

d. 2.0

Solution:

208. Given cascaded circuit; first stage is a filter circuit with insertion loss of 3 dB, followed by an amplifier with a gain of 10 dB and followed by cable having an insertion loss of 1 dB. If the input power of the filter circuit is 1 mW, find the total insertion loss.

a. 6 dBm

b. 5 dBm

c. 7 dBm

d. 2 dBm

Solution:

209. For a short circuited line or open circuited line, the standing wave ratio value is always _____.

a. Unity

b. Infinity

c. Zero

d. Cannot be determined

Solution:

210. If the voltage reading at a particular section of a transmission line is maximum, the current reading should be:

a. Maximum

b. Minimum

c. Average

d. Zero

Solution:

211. If five signals entered to an X-device at 3 dBm each, find the output power in dBm.

a. 12 dBm

b. 11 dBm

c. 10 dBm

d. 8 dBm

Solution:

212. Given incident power of 0.4 mW and insertion loss of 3 dB, find the transmitted power.

a. 0.2 mW

b. 0.3 mW

c. 0.4 mW

d. 0.5 mW

Solution:

213. The reflected voltage and reflected current along the transmission line are always:

a. 180ยฐ out of phase

b. In phase

c. Same value

d. 90ยฐ in phase

Solution:

214. If the direction of the reflection coefficient is 90ยฐ, the nature of the lien is,

a. Resistive

b. Purely inductive

c. Purely capacitive

d. None of these

Solution:

215. What are the three types of microwave transmission line?

a. Coaxial cable, open wire line, waveguide

b. Coaxial cable, stripline, waveguide

c. Open-wire line, waveguide, coaxial line

d. None of these

Solution:

216. If the incident power is -27 dBm and insertion loss of 20 dB, find for the transmitted power.

a. 12 dBm

b. 7 dBm

c. 2 dBm

d. 0 dBm

Solution:

217. Energy applied to a transmission line may become dissipated before reaching the load.

b. Conductor heating

c. Dielectric heating

d. All of the above

Solution:

218. The velocity of light is very nearly 3 x 10^8 m/s in a vacuum and ___ in all other media.

a. Higher

b. Slower

c. Same

d. All of these

Solution:

219. At a point exactly a quarter-wavelength from the load, the current is ______.

a. 180 degrees in of phase

b. 180 degrees out of phase

c. Permanently zero

d. None of these

Solution:

220. Is a piece of transmission line which is normally short-circuited at the far end.

a. Terminator

b. Stub

c. Quarter wave transformer

d. None of these

Solution:

221. For high frequencies, the best dielectric may be_______.

a. Polyethylene

b. Polyethylene foam

c. Teflon

d. None of these

Solution:

222. Characteristic impedance are sometimes called _______.

a. Ohmic resistance

b. Surge impedance

c. Wave impedance

d. None of these

Solution:

223. A transmission line is connected to a mismatched load. Calculate the VSWR in dB if the reflection coefficient is 0.25

a. 2.6 dB

b. 1.67 dB

c. 4.3 dB

d. 3.6 dB

Solution:

224. Is a power tool for the RF design

a. Calculator

b. Graphical solution

c. Smith chart

d. None of these

Solution:

225. When will the system encounter a tremendous increase of interference.

a. When return loss is 0 dB

b. When the incident power is higher than the reflected

c. When the transmission line used is coaxial cable

d. None of these

Solution:

226. In a two-stage amplifier, amplifier 1 has a noise figure of 3 dB and a gain of 20 dB. The second amplifier has a noise figure of 6 dB. Find the total noise figure.

a. 3.1 dB

b. 4.2 dB

c. 2.6 dB

d. 2.27 dB

Solution:

227. If the return loss is 13 dB, find the equivalent SWR.

a. 1.6

b. 3.2

c. 1.56

d. 2.6

Solution:

228. Which of the following will you choose in order to minimize mismatch?

a. SWR = 1.4

b. T1 = 0.81

c. Return loss = 20 dB

d. None of these

Solution:

229. If the equipment has input power of 33 dBm, what is the gain of the resulting output power is 10 dBm.

a. -26 dBm

b. -23 dBm

c. -33 dBm

d. 33 dBm

Solution:

230. A stripline transmission line is built on a 4 mm thick printed wiring board that has a relative dielectric constant of 5.5. Calculate the characteristics impedance of the width of the strip is 2 mm.

a. 256 ohms

b. 321 ohms

c. 126 ohms

d. 425.35 ohms

Solution:

231. A 50 ohms transmission line is connected to a 30 ohm resistive load. Calculate reflection coefficient.

a. 0.35

b. 0.25

c. 0.10

d. 0.15

Solution:

232. The term _________ implies a sine wave of constant amplitude, phase and frequency.

b. State of constant

c. State of calamity

d. Constant sine wave

Solution:

233. Is defined as the ratio of the reflected signal to the incident signal.

a. VSWR

b. SWR

c. Reflection coefficient

d. None of these

Solution:

234. It is a measure of one way loss of power in a transmission line due to reflection from the load.

a. Return loss

b. Transmission loss

c. Propagation loss

d. None of these

Solution:

235. If the velocity factor is equal to 0.66, the speed of light will be_____.

a. Increase

b. Decrease

c. Same

d. None of these

Solution:

236. In 1939, _________ published a graphical device for solving transmission line design.

a. Phillip A. Smith

b. Phillip R. Smith

c. Phillip H. Smith

d. Phillip S. Smith

Solution:

237. In order to make the smith chart universal, the impedances along the pure resistance line are _________.

a. Normal

b. Normalized

c. Open circuit

d. Short circuit

Solution:

238. Calculate the gain off an amplifier with an input power 10 kW and an output power of 200 kW.

a. 15 dB

b. 13 dB

c. 20 dB

d. 10 dB

Solution:

239. A perfect termination for a transmission line.

a. Receiving end

c. Antenna

d. Terminal end

Solution:

240. It can be measured, and includes losses due to reflection and absorption inside the component

b. Attenuation

c. Insertion loss

d. Return loss

Solution:

241. A component that samples the microwave signal traveling in one direction down a transmission line

a. Isolator

b. Directional coupler

c. Combiner

d. attenuator

Solution:

242. A transmission line having air dielectric is operated at a frequency of 110 MHz. What is the phase shift constant of the line is degrees per inch?

a. 2.56

b. 3.35

c. 4.6

d. 1.25

Solution:

243. Consider the three networks in series, the first is an attenuator with a 12 dB loss, the second network is an amplifier with 35 dB gain, and the third has an insertion loss of 10 dB. The input of the first network is 4 mW; what is the output of the third network in watts?

a. 0.798 W

b. 0.00798 W

c. 0.0798 W

d. 798 W

Solution:

244. Is a power level related to 1 mW.

a. dB

b. dBm

c. dBM

d. dBW

Solution:

245. A transmission unit used in a number of Northern European countries as an alternative to the decibel is ________.

a. Attenuation

b. Loss

c. Neper

d. dB loss

Solution:

246. Adding two +30 dBm will produce how much dBm at the output.

a. 60 dBm

b. 15 dBm

c. 23 dBm

d. 33 dBm

Solution:

247. Determines how the voltage or current decreases with distance

a. Phase-shift coefficient

b. Attenuation coefficient

c. Propagation coefficient

d. Numerical coefficient

Solution:

248. Determines the phase angle of the voltage or current variation with distance

a. Phase-shift coefficient

b. Attenuation coefficient

c. Propagation coefficient

d. Numerical coefficient

Solution:

249. Determines variation of voltage or current with distance along transmission line

a. Phase-shift coefficient

b. Attenuation coefficient

c. Propagation coefficient

d. Numerical coefficient

Solution:

250. The R, L, G, and C in the transmission line are called________.

a. Passive elements

b. Active elements

c. Line primary constant

d. Reactances

Solution:

#### Questions and Answers in Transmission Fundamentals Series

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

MCQ in Transmission Fundamentals
PART 1: MCQ from Number 1 โ 50                        Answer key: PART 1
PART 2: MCQ from Number 51 โ 100                   Answer key: PART 2
PART 3: MCQ from Number 101 โ 150                 Answer key: PART 3
PART 4: MCQ from Number 151 โ 200                 Answer key: PART 4
PART 5: MCQ from Number 201 โ 250                 Answer key: PART 5
PART 6: MCQ from Number 251 โ 300                 Answer key: PART 6
PART 7: MCQ from Number 301 โ 350                 Answer key: PART 7
PART 8: MCQ from Number 351 โ 400                 Answer key: PART 8
PART 9: MCQ from Number 401 โ 450                 Answer key: PART 9
PART 10: MCQ from Number 451 โ 500                Answer key: PART 10

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

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