This is the Multiples 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.

### Multiple Choice Questions 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**

### Continue Part V of the Series

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

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

- a. 1%
- b. 10%
- c. 5%
- d. 20%

203. Convert “ten times bigger” to the equivalent numerical dB

- a. 20 dB
- b. 15 dB
- c. 5 dB
- d. 10 dB

204. Convert “one-half as large” to equivalent numerical dB

- a. 3 dB
- b. -3 dB
- c. 2 dB
- d. -2 dB

205. Special semiconductor diode use for electronically adjustable attenuation

- a. Ideal diode
- b. PIN diode
- c. Zener diode
- d. Tunel diode

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

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

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

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

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

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

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

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

- a. 180
^{o} out of phase
- b. In phase
- c. Same value
- d. 90
^{o} in phase

214. If the direction of the reflection coefficient is 90^{o}, the nature of the lien is,

- a. Resistive
- b. Purely inductive
- c. Purely capacitive
- d. None of these

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

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

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

- a. Radiation
- b. Conductor heating
- c. Dielectric heating
- d. All of the above

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

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

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

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

- a. Polyethylene
- b. Polyethylene foam
- c. Teflon
- d. None of these

222. Characteristic impedance are sometimes called _______.

- a. Ohmic resistance
- b. Surge impedance
- c. Wave impedance
- d. None of these

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

224. Is a power tool for the RF design

- a. Calculator
- b. Graphical solution
- c. Smith chart
- d. None of these

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

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

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

- a. 1.6
- b. 3.2
- c. 1.56
- d. 2.6

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

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

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

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

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

- a. Steady state
- b. State of constant
- c. State of calamity
- d. Constant sine wave

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

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

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

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

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

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

239. A perfect termination for a transmission line.

- a. Receiving end
- b. Load
- c. Antenna
- d. Terminal end

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

- a. Fading
- b. Attenuation
- c. Insertion loss
- d. Return loss

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

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

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

244. Is a power level related to 1 mW.

- a. dB
- b. dBm
- c. dBM
- d. dBW

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

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

247. Determines how the voltage or current decreases with distance

- a. Phase-shift coefficient
- b. Attenuation coefficient
- c. Propagation coefficient
- d. Numerical coefficient

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

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

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

251. Two wire line is usually operated in the:

- a. Balanced mode
- b. Unbalanced mode
- c. High frequency
- d. None of these

252. When the load impedance doesn’t not match the line impedance, part of the energy in the incident wave is ________ at the load.

- a. Forwarded
- b. Reflected
- c. Same
- d. None of these

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