Wednesday, November 26, 2014

Transmission Fundamentals - MCQs Part V - Answers

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Answers in Transmission Fundamentals - MCQs Part V

Below are the answers key for the Multiple Choice Questions in Transmission Fundamentals - MCQs Part 5.

201. -10 dB

202. 1%

203. 10 dB

204. -3 dB

205. PIN diode

206. 31 ohm, 80.5 ohm

207. 1.5

208. 6 dBm

209. Infinity

210. Minimum

211. 10 dBm

212. 0.2 mW

213. 180o out of phase

214. Purely inductive

215. Coaxial cable, stripline, waveguide

216. 7 dBm

217. All of the above

218. Slower

219. Permanently zero

220. Stub

221. Teflon

222. Surge impedance

223. 4.3 dB

224. Smith chart

225. When return loss is 0 dB

226. 3.1 dB

227. 1.56

228. T1 = 0.81

229. -23 dBm

230. 321 ohms

231. 0.25

232. Steady state

233. Reflection coefficient

234. Transmission loss

235. Decrease

236. Phillip H. Smith

237. Normalized

238. 13 dB

239. Load

240. Insertion loss

241. Directional coupler

242. 3.35

243. 0.0798 W

244. dBm

245. Neper

246. d. 33 dBm

247. Attenuation coefficient

248. Phase-shift coefficient

249. Propagation coefficient

250. Line primary constant

251. Balanced mode

252. Reflected

The 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

Complete List of MCQs in Communications Engineering per topic


Published by: Froyd Wess23:17

Transmission Fundamentals - MCQs Part V

Filed under:

MCQs in Transmission Fundamentals - Part V

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
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 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. 180o out of phase
  • b. In phase
  • c. Same value
  • d. 90o in phase

214. If the direction of the reflection coefficient is 90o, 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 108 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


Published by: Froyd Wess23:11

Miscellaneous MCQs in Communications Engineering Part VIII - Answers

Filed under:

Answers in Miscellaneous MCQs in Communications Engineering Part VIII

Below are the answers key for the Miscellaneous Multiple Choice Questions in Communications Engineering Part 8.

351. ______ are transmission circuits interconnecting two different switching centers.

  • a. Toll center
  • b. Trunk circuits
  • c. Hybrid circuits
  • d. Intertoll circuits

352. The phone system begins with ______, which is the pair of wires that connects the central office to the user’s phone.

  • a. Loop extenders
  • b. Local change
  • c. Switching office
  • d. Local loop

353. When you dial the digit “8”, the corresponding low and high group tones are generated by the phone and sent to the central office are______.

  • a. 852 and 1336 Hz
  • b. 770 and 679 Hz
  • c. 941 and 1477 Hz
  • d. 770 and 1209 Hz

354. A signal travels via cables (propagation velocity 0.7 c) from New York to Los Angeles, a distance of 3000 miles. What are the talker echo and listener echo times?

  • a. 46 ms and 78 ms
  • b. 38 ms and 69 ms
  • c. 46 ms and 69 ms
  • d. 38 ms and 78 ms

355. The word telephone is derived from the Greek word tele, meaning _____, and phone, meaning ________.

  • a. Type, audio
  • b. Far, sound
  • c. Scope, sound
  • d. Far, handset

356. What are the second harmonics of the tones for the digit “3”?

  • a. 1540, 2954 Hz
  • b. 1394, 2954 Hz
  • c. 770, 1209 Hz
  • d. 1714, 1852 Hz

357. A European unit of the traffic intensity equal to 1/30 of an Erlang.

  • a. Call second
  • b. EBHC
  • c. Erlang
  • d. Call minute

358. A two state switching device containing one or more elements that have a low transmission impedance in one state and a very high one in the others.

  • a. Crosspoint
  • b. Coordinate switch
  • c. Folded Network
  • d. Expansions

359. Is the representation of a speech signal or other analog signal by sampling at a regular rate and converting each sample to binary numbers.

  • a. QAM
  • b. FSK
  • c. PCM
  • d. PAM

360. A murray loop is connected to locate a ground in cable between two cities 64 km apart. The lines forming the loop are identical. With the bridge balanced, R1 = 645 ohms and R2 = 476 ohms. How far is the grounded point (p) from the test end.

  • a. 35.45 km
  • b. 26.28 km
  • c. 72.06 km
  • d. 54.35 km

361. Refers to the specific of how these various waves travel under different circumstances.

  • a. Scatter
  • b. Propagation
  • c. Waveguide propagation
  • d. radiation

362. Travel in a straight line from the transmitting antenna to the receiving antenna.

  • a. Ground wave
  • b. Scatter
  • c. Space wave
  • d. Sky wave

363. Are intended to pass through the earth’s ionosphere and into space, or travel from a spaced-based transmitter to a receiver on the ground.

  • a. Satellite waves
  • b. Ground waves
  • c. Line of sight
  • d. None of these

364. Ducting is also called____.

  • a. Super ducting
  • b. Superrefraction
  • c. Superdiffraction
  • d. refraction

365. Frequencies in the UHF range propagate by means of

  • a. Ground wave
  • b. Surface wave
  • c. Sky wave
  • d. Space wave

366. An electromagnetic wave travel in free space, only one of the following can happen to them.

  • a. Absorption
  • b. Attenuation
  • c. Refraction
  • d. reflection

367. VLF waves are for some types of services because

  • a. Of low powers required
  • b. They are very reliable
  • c. The transmitting antennas are of convenient size
  • d. They penetrate the ionosphere easily

368. A region where the air pressure is so low that the free electron and ions can move about for some time without getting close enough to recombine into neutral atoms.

  • a. Ionosphere
  • b. Troposphere
  • c. Sky
  • d. Sky wave propagation

369. ________ is the distance between two wave fronts having the same phase at any given instant.

  • a. Wavefront
  • b. Wavelength
  • c. Wave distance
  • d. Field intensity

370. Modulation is used to ________.

  • a. Increase the carrier power
  • b. Reduce bandwidth used
  • c. Allow the use of practical antennas
  • d. Shorten the transmission channel

371. A pre-emphasis circuit improves the signal-to-noise of an FM signal by __________.

  • a. Amplifying the higher audio frequency
  • b. Boosting the bass frequency
  • c. Amplifying the whole frequency
  • d. Increase the carrier power

372. In an AM broadcast super heterodyne receiver, the

  • a. Local oscillator operates below the signal frequency
  • b. Mixer input must be tuned to the signal frequency
  • c. Local oscillator frequency normally double the IF
  • d. RF amplifiers normally works at 455 kHz above the carrier frequency

373. Carriers are spaced at 20 kHz, beginning at 100 kHz. Each carrier is modulated by a signal with 5 kHz bandwidth. Is there interference from sideband overlap?

  • a. No
  • b. Yes
  • c. Maybe
  • d. Sure

374. The modulated peak value of a signal is 10 V and the unmodulated carrier value is 8V. What is the modulated index?

  • a. 0.80
  • b. 0.25
  • c. 0.50
  • d. 0.75

375. What is the maximum suppression for a phase error of 2o?

  • a. 41.2 dB
  • b. 35.2 dB
  • c. 23.6 dB
  • d. 12.7 dB

376. An information signal that is sent directly without modulating any carrier is called _________.

  • a. Modulating frequency
  • b. Baseband AM
  • c. Carrier frequency
  • d. Broadband AM

377. Superheterodyne receiver was invented by

  • a. A.H. Armstrong
  • b. H.E. Armstrong
  • c. E.H. Armstrong
  • d. H.A. Armstrong

378. Convert the RF signal to the intermediate frequency,

  • a. Mixer
  • b. Local oscillator
  • c. Mixer and local oscillator
  • d. Mixer and IF stage

379. ______ is a very important part of the receiving system.

  • a. RF amplifier
  • b. Mixer
  • c. Detector
  • d. AGC

380. The frequency used for out of band signaling under CCITT standard.

  • a. 3825 Hz
  • b. 3700 Hz
  • c. Both a and b
  • d. Either a and b

381. The following are advantages of the optical fiber except _____.

  • a. Greater capacity
  • b. Crosstalk immunity
  • c. Safer to handle
  • d. Lower initial cost of installation

382. The frequencies used for fiber optic system

  • a. 1014 to 1015 Hz
  • b. 107 to 1010 Hz
  • c. 109 to 1012 Hz
  • d. 1011 to 1011 Hz

383. Plastic fibers have the following advantage over glass fiber:

  • a. Flexibility
  • b. Ruggedness
  • c. Ease of installation
  • d. Low attenuation

384. A site that contains the cellular radio equipment. It can have one or more _____.

  • a. Base
  • b. Central Business District
  • c. boundary
  • d. Coverage

385. A modulated method using frequency changes to transmit data. Usually only two frequencies are used.

  • a. FM
  • b. GSM
  • c. FSK
  • d. FCC

386. Is contained in the NAM (Number Assignment Module)

  • a. ERP
  • b. FDMA
  • c. DTMF
  • d. ESN

387. The amount of attenuation present in a waveguide is due to _________.

  • a. The air dielectric filling the guide
  • b. The fine coating of silver inside
  • c. Losses the conducting walls of the guide
  • d. I2R loss

388. The advantage of microwave baseband repeater over heterodyne repeater is:

  • a. It improve noise performance
  • b. It increase power output
  • c. It provide drops and inserts
  • d. All of these

389. The correctness and accuracy of the transmitted message content is:

  • a. Verified by the modem
  • b. Determined by the sender and receiver, not by the communications system.
  • c. Ensured by use of digital techniques
  • d. All of these

390. Transmission of binary signals requires ________.

  • a. Less bandwidth than analog
  • b. More bandwidth than analog
  • c. The same bandwidth as analog
  • d. A license from the FAA

391. Which of the following is a characteristic of a LAN?

  • a. Parallel transmission
  • b. Unlimited expansion
  • c. Low cost access for low bandwidth channels
  • d. Application independent interfaces

392. ADF means

  • a. Audio Direction Findings
  • b. Automatic Direction Finder
  • c. Automatic Detection Finder
  • d. Alternate Detection Form

393. A navigational system which employs gyroscopes, accelerometers and associated electronics to sense burning rates and accelerations associated with the rotation of the earth.

  • a. CNS
  • b. INS
  • c. GPS
  • d. VOR

394. It is referred to as the range and azimuth display.

  • a. A-scan
  • b. B-Scan
  • c. C-Scan
  • d. PPI

395. GCA operates with:

  • a. DME
  • b. Master and slave stations
  • c. Ground-based radar
  • d. Local radio stations

396. Bass response means:

  • a. Maximum high frequency response
  • b. Emphasizing the high audio frequencies
  • c. By passing high audio frequencies
  • d. By passing low audio frequencies

397. Sound intensity varies directly to the square of:

  • a. Density
  • b. Velocity
  • c. Pressure
  • d. frequency

398. Audience per person usually have an absorption coefficient in unit pert sq. ft. of :

  • a. 3.5
  • b. 4.7
  • c. 6.7
  • d. 7.4

399. Early reflected sound is also called as:

  • a. Echo
  • b. Reverberation
  • c. Pure sound
  • d. Intelligible sound

100. The optimum reverberation time for a 6000 cu. Ft. room is about:

  • a. 2.0 sec
  • b. 1.5 sec
  • c. 1.1 sec
  • d. 1.0 sec

Complete List of MCQs in Communications Engineering per topic


Published by: Froyd Wess22:30

Miscellaneous MCQs in Communications Engineering Part VIII

Filed under:

MCQs in Communications Engineering

This is the Miscellaneous Multiples Choice Questions Part 8 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%).

Continue with Part VIII of the Series

351. ______ are transmission circuits interconnecting two different switching centers.

  • a. Toll center
  • b. Trunk circuits
  • c. Hybrid circuits
  • d. Intertoll circuits

352. The phone system begins with ______, which is the pair of wires that connects the central office to the user’s phone.

  • a. Loop extenders
  • b. Local change
  • c. Switching office
  • d. Local loop

353. When you dial the digit “8”, the corresponding low and high group tones are generated by the phone and sent to the central office are______.

  • a. 852 and 1336 Hz
  • b. 770 and 679 Hz
  • c. 941 and 1477 Hz
  • d. 770 and 1209 Hz

354. A signal travels via cables (propagation velocity 0.7 c) from New York to Los Angeles, a distance of 3000 miles. What are the talker echo and listener echo times?

  • a. 46 ms and 78 ms
  • b. 38 ms and 69 ms
  • c. 46 ms and 69 ms
  • d. 38 ms and 78 ms

355. The word telephone is derived from the Greek word tele, meaning _____, and phone, meaning ________.

  • a. Type, audio
  • b. Far, sound
  • c. Scope, sound
  • d. Far, handset

356. What are the second harmonics of the tones for the digit “3”?

  • a. 1540, 2954 Hz
  • b. 1394, 2954 Hz
  • c. 770, 1209 Hz
  • d. 1714, 1852 Hz

357. A European unit of the traffic intensity equal to 1/30 of an Erlang.

  • a. Call second
  • b. EBHC
  • c. Erlang
  • d. Call minute

358. A two state switching device containing one or more elements that have a low transmission impedance in one state and a very high one in the others.

  • a. Crosspoint
  • b. Coordinate switch
  • c. Folded Network
  • d. Expansions

359. Is the representation of a speech signal or other analog signal by sampling at a regular rate and converting each sample to binary numbers.

  • a. QAM
  • b. FSK
  • c. PCM
  • d. PAM

360. A murray loop is connected to locate a ground in cable between two cities 64 km apart. The lines forming the loop are identical. With the bridge balanced, R1 = 645 ohms and R2 = 476 ohms. How far is the grounded point (p) from the test end.

  • a. 35.45 km
  • b. 26.28 km
  • c. 72.06 km
  • d. 54.35 km

361. Refers to the specific of how these various waves travel under different circumstances.

  • a. Scatter
  • b. Propagation
  • c. Waveguide propagation
  • d. radiation

362. Travel in a straight line from the transmitting antenna to the receiving antenna.

  • a. Ground wave
  • b. Scatter
  • c. Space wave
  • d. Sky wave

363. Are intended to pass through the earth’s ionosphere and into space, or travel from a spaced-based transmitter to a receiver on the ground.

  • a. Satellite waves
  • b. Ground waves
  • c. Line of sight
  • d. None of these

364. Ducting is also called____.

  • a. Super ducting
  • b. Superrefraction
  • c. Superdiffraction
  • d. refraction

365. Frequencies in the UHF range propagate by means of

  • a. Ground wave
  • b. Surface wave
  • c. Sky wave
  • d. Space wave

366. An electromagnetic wave travel in free space, only one of the following can happen to them.

  • a. Absorption
  • b. Attenuation
  • c. Refraction
  • d. reflection

367. VLF waves are for some types of services because

  • a. Of low powers required
  • b. They are very reliable
  • c. The transmitting antennas are of convenient size
  • d. They penetrate the ionosphere easily

368. A region where the air pressure is so low that the free electron and ions can move about for some time without getting close enough to recombine into neutral atoms.

  • a. Ionosphere
  • b. Troposphere
  • c. Sky
  • d. Sky wave propagation

369. ________ is the distance between two wave fronts having the same phase at any given instant.

  • a. Wavefront
  • b. Wavelength
  • c. Wave distance
  • d. Field intensity

370. Modulation is used to ________.

  • a. Increase the carrier power
  • b. Reduce bandwidth used
  • c. Allow the use of practical antennas
  • d. Shorten the transmission channel

371. A pre-emphasis circuit improves the signal-to-noise of an FM signal by __________.

  • a. Amplifying the higher audio frequency
  • b. Boosting the bass frequency
  • c. Amplifying the whole frequency
  • d. Increase the carrier power

372. In an AM broadcast super heterodyne receiver, the

  • a. Local oscillator operates below the signal frequency
  • b. Mixer input must be tuned to the signal frequency
  • c. Local oscillator frequency normally double the IF
  • d. RF amplifiers normally works at 455 kHz above the carrier frequency

373. Carriers are spaced at 20 kHz, beginning at 100 kHz. Each carrier is modulated by a signal with 5 kHz bandwidth. Is there interference from sideband overlap?

  • a. No
  • b. Yes
  • c. Maybe
  • d. Sure

374. The modulated peak value of a signal is 10 V and the unmodulated carrier value is 8V. What is the modulated index?

  • a. 0.80
  • b. 0.25
  • c. 0.50
  • d. 0.75

375. What is the maximum suppression for a phase error of 2o?

  • a. 41.2 dB
  • b. 35.2 dB
  • c. 23.6 dB
  • d. 12.7 dB

376. An information signal that is sent directly without modulating any carrier is called _________.

  • a. Modulating frequency
  • b. Baseband AM
  • c. Carrier frequency
  • d. Broadband AM

377. Superheterodyne receiver was invented by

  • a. A.H. Armstrong
  • b. H.E. Armstrong
  • c. E.H. Armstrong
  • d. H.A. Armstrong

378. Convert the RF signal to the intermediate frequency,

  • a. Mixer
  • b. Local oscillator
  • c. Mixer and local oscillator
  • d. Mixer and IF stage

379. ______ is a very important part of the receiving system.

  • a. RF amplifier
  • b. Mixer
  • c. Detector
  • d. AGC

380. The frequency used for out of band signaling under CCITT standard.

  • a. 3825 Hz
  • b. 3700 Hz
  • c. Both a and b
  • d. Either a and b

381. The following are advantages of the optical fiber except _____.

  • a. Greater capacity
  • b. Crosstalk immunity
  • c. Safer to handle
  • d. Lower initial cost of installation

382. The frequencies used for fiber optic system

  • a. 1014 to 1015 Hz
  • b. 107 to 1010 Hz
  • c. 109 to 1012 Hz
  • d. 1011 to 1011 Hz

383. Plastic fibers have the following advantage over glass fiber:

  • a. Flexibility
  • b. Ruggedness
  • c. Ease of installation
  • d. Low attenuation

384. A site that contains the cellular radio equipment. It can have one or more _____.

  • a. Base
  • b. Central Business District
  • c. boundary
  • d. Coverage

385. A modulated method using frequency changes to transmit data. Usually only two frequencies are used.

  • a. FM
  • b. GSM
  • c. FSK
  • d. FCC

386. Is contained in the NAM (Number Assignment Module)

  • a. ERP
  • b. FDMA
  • c. DTMF
  • d. ESN

387. The amount of attenuation present in a waveguide is due to _________.

  • a. The air dielectric filling the guide
  • b. The fine coating of silver inside
  • c. Losses the conducting walls of the guide
  • d. I2R loss

388. The advantage of microwave baseband repeater over heterodyne repeater is:

  • a. It improve noise performance
  • b. It increase power output
  • c. It provide drops and inserts
  • d. All of these

389. The correctness and accuracy of the transmitted message content is:

  • a. Verified by the modem
  • b. Determined by the sender and receiver, not by the communications system.
  • c. Ensured by use of digital techniques
  • d. All of these

390. Transmission of binary signals requires ________.

  • a. Less bandwidth than analog
  • b. More bandwidth than analog
  • c. The same bandwidth as analog
  • d. A license from the FAA

391. Which of the following is a characteristic of a LAN?

  • a. Parallel transmission
  • b. Unlimited expansion
  • c. Low cost access for low bandwidth channels
  • d. Application independent interfaces

392. ADF means

  • a. Audio Direction Findings
  • b. Automatic Direction Finder
  • c. Automatic Detection Finder
  • d. Alternate Detection Form

393. A navigational system which employs gyroscopes, accelerometers and associated electronics to sense burning rates and accelerations associated with the rotation of the earth.

  • a. CNS
  • b. INS
  • c. GPS
  • d. VOR

394. It is referred to as the range and azimuth display.

  • a. A-scan
  • b. B-Scan
  • c. C-Scan
  • d. PPI

395. GCA operates with:

  • a. DME
  • b. Master and slave stations
  • c. Ground-based radar
  • d. Local radio stations

396. Bass response means:

  • a. Maximum high frequency response
  • b. Emphasizing the high audio frequencies
  • c. By passing high audio frequencies
  • d. By passing low audio frequencies

397. Sound intensity varies directly to the square of:

  • a. Density
  • b. Velocity
  • c. Pressure
  • d. frequency

398. Audience per person usually have an absorption coefficient in unit pert sq. ft. of :

  • a. 3.5
  • b. 4.7
  • c. 6.7
  • d. 7.4

399. Early reflected sound is also called as:

  • a. Echo
  • b. Reverberation
  • c. Pure sound
  • d. Intelligible sound

100. The optimum reverberation time for a 6000 cu. Ft. room is about:

  • a. 2.0 sec
  • b. 1.5 sec
  • c. 1.1 sec
  • d. 1.0 sec

Complete List of MCQs in Communications Engineering per topic


Published by: Froyd Wess22:14

Miscellaneous MCQs in Communications Engineering Part VII - Answers

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Answers in Miscellaneous MCQs in Communications Engineering Part VII

Below are the answers key for the Miscellaneous Multiple Choice Questions in Communications Engineering Part 7.

301. 6

302. Standing wave ratio

303. Polyethylene coaxial line

304. 1.0

305. 6.9 kW

306. AGC

307. Maximum Usable Frequency (MUF)

308. Dead zone

309. Double

310. One

311. shroud

312. Radiation pattern

313. 1.76 dB

314. Impulse noise

315. Pressure

316. trough

317. Diaphragm and generating element

318. Multipath reception

319. Class B

320. Convergence

321. QAM

322. HRC

323. All of the above

324. 26.9 kbps

325. 672

326. NRM (Normal Response Mode)

327. Flag

328. queueing

329. ASR

330. Duplexer

331. Phased Array

332. Aperture

333. End-fire array

334. 42.67 dB

335. Cassegrain feed

336. Horn antennas

337. Cass-horn antennas

338. 8 m

339. 55o

340. Loop antennas

341. Antenna current

342. 88.1

343. Chrominance subcarrier

344. Monochrome transmission

345. Center frequency

346. Pilot sub-carrier

347. Frequency deviation

348. Sound

349. Beam tilt

350. 1,000

Complete List of MCQs in Communications Engineering per topic


Published by: Froyd Wess21:43

Miscellaneous MCQs in Communications Engineering Part VII

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MCQs in Communications Engineering

This is the Miscellaneous Multiples Choice Questions Part 7 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%).

Continue with Part VII of the Series

301. In reducing the voltage by ½, there is a decrease of _____.

  • a. 2
  • b. 3
  • c. 4
  • d. 6

302. A measure if mismatch in a transmission line.

  • a. Reflection coefficient
  • b. Propagation delay
  • c. Standing wave ratio
  • d. All of these

303. Which type of transmission line has the least velocity factor?

  • a. Air-insulated parallel line
  • b. Air insulated coaxial line
  • c. Polyethylene parallel line
  • d. Polyethylene coaxial line

304. It is required to match a 73 ohm antenna to a 600 ohm transmission line, with a velocity factor of 0.66, by means of a quarter-wave matching transformer. At a frequency of 150 MHz, calculate the length of matching section, in feet.

  • a. 2,2
  • b. 0.8
  • c. 1.0
  • d. 1.8

305. A transmitter radiates 5 kW with unmodulated carrier but when the carrier is sinusoidally modulated, it radiates 6.5 kW. Now, another sine wave corresponding to 40% modulation is transmitted simultaneously. Determine the total radiated power.

  • a. 6.9 kW
  • b. 6.5 kW
  • c. 6.4 kW
  • d. 7.6 kW

306. A circuit which is used to keep the signal levels approximately constant in the RF stage and the mixer of an FM receiver.

  • a. AGC
  • b. AFC
  • c. Local oscillator
  • d. Limiter

307. The highest frequency that can be set back to earth by the ionosphere, if the wave is sent vertically upward.

  • a. Maximum Usable Frequency (MUF)
  • b. Critical frequency
  • c. Propagating frequency
  • d. Cut-off frequency

308. The difference between the farthest point the direct wave extend and the nearest point the sky wave reflected to ground.

  • a. Skip distance
  • b. Radio horizon distance
  • c. Dead zone
  • d. Fresnel zone

309. Power density is defined as radiated power per unit area, it follows that power density is reduced to ¼ of its value when distance from the source is____.

  • a. Double
  • b. Three-fold
  • c. Four-fold
  • d. Five fold

310. If the clearance above the obstruction is equal to the second Fresnel zone, the path of the reflection wave is physically _____ wavelength longer than the direct wave.

  • a. One-half
  • b. One
  • c. Two
  • d. three

311. Attached around the rim of the parabolic antenna to eliminate side-lobes causing interference to nearby microwave station.

  • a. Radome
  • b. Feed-horn
  • c. Reflector
  • d. shroud

312. It is polar diagram representing field strengths or power densities at various angular positions

  • a. Lobe
  • b. Radiation pattern
  • c. Beamwidth
  • d. All of these

313. The gain of a Hertzian dipole with respect to an isotropic antenna.

  • a. 4.15 dB
  • b. 2.15 dB
  • c. 1.76 dB
  • d. 5.15 dB

314. A kind of noise in the form of randomly occurring spikes.

  • a. White noise
  • b. Impulse noise
  • c. Johnson noise
  • d. Thermal noise

315. Sound intensity varies directly to square of

  • a. Velocity
  • b. Density
  • c. Pressure
  • d. frequency

316. Rarefraction produces

  • a. crest
  • b. sound
  • c. vibration
  • d. trough

317. What are the basic components of a microphone?

  • a. Coil and magnet
  • b. Ceramic and crystal
  • c. Diaphragm and generating element
  • d. Wired and body

318. A cause for ghost and smears

  • a. Multipath reception
  • b. Open transmission line
  • c. Improperly positioned antenna
  • d. All of these

319. An FM broadcast station with an ERP of not more than 35 kW.

  • a. Clear channel
  • b. Class A
  • c. Class B
  • d. Regional Channel

320. In television-receiver, the alignment of all these colors guns to a common point is referred to as _____.

  • a. Confetti
  • b. Convergence
  • c. Demodulation
  • d. blooming

321. It is a form of digital modulation where the digital information is contained in both the amplitude and phase of the transmitted carrier.

  • a. QAM
  • b. FSK
  • c. PCM
  • d. PSK

322. An error detection scheme that uses parity to determine if transmission error has occurred in a message.

  • a. CRC
  • b. VRC
  • c. HRC
  • d. All of the above

323. Synchronization modem usually contains a

  • a. Scrambler
  • b. Descrambler
  • c. Adaptive equalizers
  • d. All of the above

324. For a standard voice band communications channel with a S/N of 30 dB and a bandwidth of 2.7 kHz, the Shannon limit for information capacity is _______.

  • a. 8.1 kbps
  • b. 12.4 kbps
  • c. 4.03 kbps
  • d. 26.9 kbps

325. A T3 carrier time division multiplexes _______ PCM-encoded voice channels.

  • a. 692
  • b. 672
  • c. 96
  • d. 4032

326. In this mode, a secondary station can not initiate transmission without first receiving permission from the primary station.

  • a. NRM (Normal Response Mode)
  • b. ARM (Asynchronous Response Mode)
  • c. ABM (Asynchronous Balanced Mode)
  • d. LAP (Link Access Protocol)

327. With bit-oriented protocol, a frame starts with a ______.

  • a. Pad
  • b. Start bit
  • c. Flag
  • d. header

328. The controller provides

  • a. queueing
  • b. line querying
  • c. companding
  • d. buffering

329. A radar equipment located near the runway designed to accurately locate an airplane with 300 ft. of range.

  • a. ASR
  • b. PAR
  • c. ILS
  • d. ARSR

330. A circuit in a radar used to allow an antenna to function as a transmitting and a receiving antenna.

  • a. Diplexer
  • b. Duplexer
  • c. Combiner
  • d. Matrix

331. Is an electronically steerable antenna.

  • a. Yagi-Uda
  • b. Log Periodic
  • c. Phased Array
  • d. None of these

332. The ratio of the focal length to the mouth diameter of the parabola is called _______.

  • a. Aperture Number
  • b. Aperture diameter
  • c. Effective area
  • d. Aperture

333. Is an array antenna which has its maximum main beam directed along the axis of the array.

  • a. Antenna array
  • b. End-fire array
  • c. Broadside array
  • d. None of these

334. The dish antenna is operating at 10 GHz frequency. What is the directivity if the reflector is 5m at 65% efficiency?

  • a. 18.703 dB
  • b. 42.67 dB
  • c. 13.6 dB
  • d. 12.2 dB

335. It uses a hyperboloid secondary reflector.

  • a. Double reflector
  • b. Waveguide feed horn
  • c. Feed horn
  • d. Cassegrain feed

336. When a waveguide is terminated by a horn, it is called ______.

  • a. Feed antennas
  • b. Horn antennas
  • c. Feed horn
  • d. None of these

337. Radio waves are collected by the large bottom surface which is a slightly curved and are reflected upward at an angle of 45o, upon hitting the top surface which is large hyperbolic cylinder, they are reflected downward to the focal point and collected by the conical horn placed at the focus.

  • a. Horn antennas
  • b. Helical antennas
  • c. Discone antennas
  • d. Cass-horn antennas

338. Calculate the effective length of an antenna which has directive gain over an isotropic antenna of 17 dB and a radiation resistance of 350 ohms at a frequency of 144 MHz.

  • a. 8 m
  • b. 10 m
  • c. 5 m
  • d. 7 m

339. Calculate the angular aperture for a paraboloid reflector antennas for which the aperture number 0.48.

  • a. 37o
  • b. 55o
  • c. 65o
  • d. 28o

340. Is made up of one or more turns of wire on a frame which may be rectangular or circular, and is very much smaller than one wavelength across.

  • a. Circular antennas
  • b. Helical antennas
  • c. Loop antennas
  • d. None of these

341. Is the radio-frequency current on the antenna with no modulation.

  • a. Carrier current
  • b. Antenna current
  • c. Current
  • d. None of these

342. Channels for FM broadcast station begin at ____ MHz and continue is successive steps of 200 kHz to and including 107.9 MHz

  • a. 89.1
  • b. 88.1
  • c. 89.9
  • d. None of these

343. The carrier which is modulated by the chrominance information.

  • a. Carrier frequency
  • b. IF frequency
  • c. Chrominance subcarrier
  • d. Color burst

344. The transmission of television signal which can be reproduced is gradations of a single color only.

  • a. Monochrome transmission
  • b. Negative transmission
  • c. Color transmission
  • d. Video transmission

345. The carrier frequency allocated by the authority.

  • a. Frequency swing
  • b. High frequency
  • c. Center frequency
  • d. IF frequency

346. Serving as a control signal for use in the reception of FM stereophonic broadcast.

  • a. IF frequency
  • b. Pilot sub-carrier
  • c. RF frequency
  • d. Carrier frequency

347. The peak difference between the instantaneous frequency of the modulated wave and carrier frequency.

  • a. Modulated index
  • b. Frequency deviation
  • c. Modulating frequency
  • d. Percentage modulation

348. AM Broadcast station licensed for aural or _____ transmission intended for direct reception by the general public and operated on a channel in the medium frequency band.

  • a. Video
  • b. Carrier
  • c. Sound
  • d. Power

349. Is necessary to bring the main vertical beam tangential to the earth, which is curving away from it.

  • a. Radio horizon
  • b. Take off angle
  • c. Money
  • d. Beam tilt

350. In Metro Manila and Metro Cebu, the maximum effective radiated power of 350 kW for channel 2 - 6 and ____ kW for channel 7 – 13 are allowed.

  • a. 1,000
  • b. 5000
  • c. 500
  • d. 250

Complete List of MCQs in Communications Engineering per topic


Published by: Froyd Wess21:41

Miscellaneous MCQs in Communications Engineering Part VI - Answers

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Answers in Miscellaneous MCQs in Communications Engineering Part VI

Below are the answers key for the Miscellaneous Multiple Choice Questions in Communications Engineering Part 6.

251. 10 Base-5

252. Alias

253. Dc

254. 1000 Base-T

255. Run length code

256. Discrete Cosine Transform

257. 150 ft

258. use 8-bit PCM code and include 24 voice channel

259. Octet

260. 6

261. Interleaving

262. WIMAX

263. 25x15mm

264. 1 Hz to 150MHz

265. Preamble

266. a flow of loop current

267. 36 kHz

268. Equal-loudness Contour

269. Class 5

270. Cybernetics

271. 51.84 Mbps

272. 1.33 us

273. 2 Mbps

274. 1.6db

275. are limited to small data networks

276. casual plug

277. 0.752 Vmax

278. 500 ft

279. TA

280. T1

281. 4B/5B Encoding

282. 67.5%

283. 300 MHz to 50,000 MHz

284. tandem office

285. 17.95 us

286. Condenser microphone

287. 35 W

288. 0.5Mbps

289. Munsell Color Scale

290. 1 mV

291. 68.75 us

292. V.42

293. Session Layer

294. 941 Hz and 1477 Hz

295. 14

296. INTELSAT V

297. 12.5%

298. 87.75 MHz

299. A (la)

300. Baudot code

Complete List of MCQs in Communications Engineering per topic


Published by: Froyd Wess16:22