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# MCQ in Antennas Part 5 | ECE Board Exam

This is the Multiples Choice Questions Part 5 of the Series in Antennas 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

• MCQ in Basic considerations
• MCQ in Wire Radiators in Space
• MCQ in Current and Voltage Distributions
• MCQ in Resonant and Non-resonant Antennas
• MCQ in Antenna Terms and Definition
• MCQ in Antenna Gain and Resistance
• MCQ in Bandwidth, Beamwidth and Polarization
• MCQ in Grounded and Ungrounded Antennas
• MCQ in Grounding Systems and Matching Systems
• MCQ in Antenna Types
• MCQ in Directional and Non-directional Antennas
• MCQ in Microwave Antennas
• MCQ in Wideband and Special Purpose Antennas

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

201. An ungrounded antenna near the ground

a. Acts as a single antenna of twice the height

b. Is unlikely to need an earth mat

c. Acts as an antenna array

d. Must be horizontally polarized

Solution:

202. One of the following consists of non-resonant antennas

a. Rhombic antenna

b. Folded dipole

c. End-fire array

Solution:

203. One of the following is very useful as a multiband HF receiving antenna. This is the:

a. Conical horn

b. Folded dipole

c. Log-periodic

d. Square loop

Solution:

204. Which of the following antennas is best excited from a waveguide?

a. Biconical

b. Horn

c. Helical discone

d. None of the above

Solution:

205. Indicate which of the following reasons for using a counterpoise with antennas is false:

a. Impossibility of a good ground connection

b. Protection of personnel working underneath

c. Provision of an earth for the antenna

d. Rockiness of the ground itself

Solution:

206. One of the following is not a reason for the use of an antenna coupler

a. To make the antenna look resistive

b. To provide the output amplifier with the correct load impedance

c. To discriminate against harmonics

d. To prevent re-radiation of the local oscillator

Solution:

207. Indicate the antenna that is not wideband:

a. Discone

b. Folded dipole

c. Helical

d. Marconi

Solution:

208. Indicates which of the following reasons for the use of an earth mat with antennas is false.

a. Impossibility of a good ground connection

b. Provision of an earth for the antenna

c. Protection of personnel working underneath

d. Improvement f the radiation pattern of the antenna

Solution:

209. Which of the following terms does not apply to the Yagi-Uda array?

a. Good bandwidth

b. Parasitic elements

c. Folded dipole

d. High gain

Solution:

210. An antenna that is circularly polarized is the

a. Helical

b. Small circular loop

c. Parabolic reflector

d. Yagi-Uda

Solution:

211. The standard reference antenna for the directive gain is the

a. Infinitesimal dipole

b. Isotropic antenna

c. Elementary doublet

d. Half-wave dipole

Solution:

212. Top loading is sometimes used with an antenna in order to increase its

a. Effective height

b. Bandwidth

c. Beamwidth

d. Input capacitance

Solution:

213. Cassegrain feed is used with a parabolic reflector to

a. Increase the gain of the system

b. Increase the beamwidth of the system

c. Reduce the size of the main reflector

d. Allow the feed to be placed at a convenient point

Solution:

214. Zoning is used with a dielectric antenna in order to

a. Reduce the bulk of the lens

b. Increase the bandwidth of the lens

c. Permit pin-point focusing

d. Correct the curvature if the wavefront from a horn that is too short

Solution:

215. A helical antenna is used for satellite tracking because of its

a. Circular polarization

b. Maneuverability

d. Good front-to-back ratio

Solution:

216. The discone antenna is

a. A useful direction-finding antenna

b. Used as a radar receiving antenna

c. Circularly polarized like other circular antennas

d. Useful as a HF receiving antenna

Solution:

217. One of the following is not an omnidirectional antenna:

a. Half-wave dipole

b. Log-periodic

c. Discone

d. Marconi

Solution:

218. How is it possible to lower the resonant frequency of a Hertz dipole antenna?

a. Reduce the frequency at the transmitter

b. Connect a capacitor in series with the antenna

c. Connect an inductor in series with the antenna

d. Reduce the length of the antenna

Solution:

219. Which of the following antennas receives signals in the horizontal plane equally well from all directions?

a. Horizontal Hertz antenna

b. Vertical loop antenna

c. Vertical Yagi antenna

d. A vertical antenna which is a quarter-wavelength long

Solution:

220. A one-quarter-wavelength shut-fed vertical Marconi antenna:

a. Has maximum radiation in a vertical direction

b. Must have a horizontal receiving antenna for the best reception

c. Must use a receiving antenna which has an electric field in a horizontal direction

d. Must have a vertical receiving antenna for the best reception

Solution:

221. A shunt-fed quarter-wavelength Marconi antenna:

a. Has maximum RF impedance to ground at its feedpoint

b. Has a current null at its feedpoint

c. Has zero dc resistance to ground

d. Uses balanced twin line as its feeder cable

Solution:

222. The parasitic element of an antenna system will:

a. Decrease its directivity

b. Increase its directivity

c. Give the antenna unidirectional properties

d. Both B and C

Solution:

223. If the length of the antenna is changed from 2.5 meters to 2.8 meters, its resonant frequency will

a. Increase

b. Decrease

c. Depend on the velocity factor so the resonant frequency can either be increased or decreased

d. Will be unchanged

Solution:

224. What is the effect of adding a capacitor in series with an antenna?

a. The antennaโs resonant frequency will increase

b. The antennaโs resonant frequency will decrease

c. A capacitor is never added in series with an antenna

d. The purpose is to block dc from being applied to the antenna

Solution:

225. How does the electric field strength of a broadcast station vary with the distance from the antenna?

a. The field strength varies inversely proportional to the distance from the antenna

b. The field strength is directly proportional to the square of the distance from the antenna

c. The field strength varies directly proportional to the square of the distance from the antenna

d. The field strength varies inversely as the distance from the antenna

Solution:

226. Stacking elements in a transmitting antenna system

a. Increases the field strength at the receiving antenna

b. Increases the directivity of the transmitter antenna

c. Decreases the size of the major lobe in the radiation pattern

d. Both a and b

Solution:

227. The rhombic antenna is primarily used for

a. Ground wave propagation

b. Skywave propagation

c. Space wave propagation

d. Tropospheric propagation

Solution:

228. If the antenna current is doubled, the field strength at a particular position is

a. Doubled

b. Halved

c. Multiplied by a factor of four

d. Multiplied by a factor of 1.414

Solution:

229. A vertical loop antenna has a

a. Unidirectional radiation pattern in the horizontal plane

b. Unidirectional radiation pattern in the vertical plane

c. Bidirectional radiation pattern in the horizontal plane

d. Omnidirectional radiation pattern in the horizontal plane

Solution:

230. In order to get maximum radiation to all surrounding points in the horizontal plane, the antenna used is a(an)

a. Vertical loop

b. Vertical quarter-wavelength rod

c. Array which includes parasitic elements

d. Horizontal Hertz dipole

Solution:

231. The physical length of a Hertz dipole resonant at a 100 MHz is

a. 9.84 ft

b. 4.92 ft

c. 4.68 ft

d. 2.46 ft

Solution:

232. What is meant by the term antenna gain?

a. The numerical ratio relating the radiated signal strength of an antenna to that of another antenna

b. The ratio if the signal in the forward direction to the signal in the back direction

c. The ratio of the amount of power produced by the antenna compared to the output power of the transmitter

d. The final amplifier gain minus the transmission losses

Solution:

233. What is meant by the term antenna bandwidth?

a. Antenna length divided by the number of elements

b. The frequency range over which an antenna can be expected to perform well

c. The angle between the half-power radiation points

d. The angle formed between two imaginary-lines drawn through the ends of the elements

Solution:

234. What is the wavelength of a shorted stub used to absorb even harmonics?

a. ยฝ ฮป

b. 1/3 ฮป

c. ยผ ฮป

d. 1/8 ฮป

Solution:

235. What is a trap antenna?

a. An antenna for rejecting interfering signals

b. A highly sensitive antenna with maximum gain in all directions

c. An antenna capable of being used on more than one band because of the presence of parallel LC networks

d. An antenna with a large capture area

Solution:

236. What is the disadvantage of using a trap antenna?

a. It has a high directivity in the high-frequency bands

b. It has a high gain

c. It minimizes harmonic radiation pattern

d. It may be used for multi-band operation

Solution:

237. What is the disadvantage of using a trap antenna?

b. It can only be used for single band operation

c. It is too sharply directional at lower frequencies

d. It must be neutralized

Solution:

238. What is the principle of a trap antenna?

a. Beamwidth may be controlled by nonlinear impedance

b. The traps form a high impedance to isolate parts of the antenna

c. The effective radiated power can be increased if the space around the antenna sees a high impedance

d. The traps increase the antenna gain

Solution:

239. What is a parasitic element of an antenna?

a. An element polarized 90 degrees opposite the driven element

b. An element dependent on the antenna structure for support

c. An element that receives its excitation from mutual coupling rather than from a transmission line

Solution:

240. How does a parasitic element generate an electromagnetic field?

a. By the RF current received from a connected transmission line

b. By interacting with the earthโs magnetic field

c. By altering the phase of the current on the driven element

d. By currents induced into the element from a surrounding electric field

Solution:

241. How much power will an antenna having a radiation resistance of 50 โฆ radiate when fed with a 20 A current?

a. 20, 000 W

b. 1000 W

c. 2 kW

d. 10 kW

Solution:

242. Determine the Q of an antenna if it has a bandwidth of 0.06 MHz and is cut to a frequency of 30 MHz.

a. 50

b. 100

c. 150

d. 250

Solution:

243. How does the length of the reflector element of a parasitic element beam antenna compare with that of the driven element?

a. It is about 5% longer

b. It is about 5% shorter

c. It is twice as long

d. It is one-half as long

Solution:

244. How does the length of the director element of a parasitic element beam antenna compare with that of the driven element?

a. It is about 5% longer

b. It is about 5% shorter

c. It is twice as long

d. It is one-half as long

Solution:

245. What is meant by the radiation resistance for an antenna?

a. Losses in the antenna elements and feedline

b. The specific impedance of the antenna

c. An equivalent resistance that would dissipate the same amount of power as that radiated from an antenna

d. The resistance in the trap coils to received signals

Solution:

246. What are the factors that determine the radiation resistance of an antenna?

a. Transmission line length and height of antenna

b. The locations of the antenna with respect to nearby objects and the length/diameter ratio of the conductors

c. It is a constant for all antennas since it is a physical constant

d. Sunspot activity and the time of day

Solution:

247. In a half-wave dipole, where are the current nodes?

a. At the ends

b. At the feedpoint

c. Three-quarters of the way from the feedpoint towards the end

d. One-half of the way from the feedpoint toward the end

Solution:

a. Lower Q

b. Greater structural strength

c. Higher losses

Solution:

249. What is the beamwidth of a symmetrical pattern antenna with a gain of 30 dB as compared to an isotropic radiator?

a. 3.2 degrees

b. 6.4 degrees

c. 37 degrees

d. 60.4 degrees

Solution:

250. A microwave communications uses plane reflectors as passive repeaters. The diameter of the parabolic antenna is 18 ft while the effective area is 310 sq ft. Determine the reflector coupling factor.

a. 0.76

b. 0.906

c. 0.92

d. 0.706

Solution:

#### Questions and Answers in Antennas Series

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

MCQ in Antennas
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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