MCQs in Communications Engineering Part 3

Compiled Miscellaneous Multiple Choice Questions in Communications Engineering Part 3 of the series. Familiarize each and every questions compiled here in Preparation for the ECE Board Exam

MCQs in Communications Engineering

This is the Miscellaneous Multiples Choice Questions Part 3 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%).

The Series

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

Miscellaneous Communications Engineering 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 with Part III of the Series

Choose the letter of the best answer in each questions.

101. A device launches or receives a wave in a transmission line or waveguide in one direction only.

  • a. Cross-field tube
  • b. Directional coupler
  • c. Linear-beam tube
  • d. Slow-wave structure

102. A type of linear-beam microwave tube that uses velocity modulation of the electron beam.

  • a. Buncher
  • b. Gunn device
  • c. Catcher
  • d. Klystron

103. A line of sight radio link operating at a frequency of 6 GHz has a separation of 50 km between antennas. An obstacle in the path is located 20 km from the transmitting antenna. By how much must the beam clear the obstacle?

  • a. 24.47 meters
  • b. 24.47 kilometers
  • c. 14.67 meters
  • d. 14.67 kilometers

104. Variation in received field strength over time due to changes in propagation conditions.

  • a. Fading
  • b. Fade margin
  • c. Diversity
  • d. Fresnel zones

105. Which of the following antenna types is not designed for transmitting at 10 GHz?

  • a. Horn antenna
  • b. Dish antenna
  • c. Zepp antenna
  • d. Helical antenna

106. The type of radio wave responsible for long distance communications by multiple skips is the

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

107. Line of sight communications is not a factor in which frequency range?

  • a. VHF
  • b. UHF
  • c. HF
  • d. Microwaves

108. It is often defined as the loss incurred by an electromagnetic wave as it propagates in a straight line through a vacuum with no absorption or reflection of energy from nearby objects.

  • a. Transmission loss
  • b. Atmospheric loss
  • c. Free space loss
  • d. Spreading loss

109. A type of microwave protection system where each working channel has a dedicated back up or space channel.

  • a. Diversity
  • b. Space diversity
  • c. Hybrid diversity
  • d. Hot standby

110. A laser that uses organic dyes enclosed in a glass tube for an active medium, dye is circulated into the tube with a pump. A powerful pulse of light excites the organic dye.

  • a. Solid laser
  • b. Gas laser
  • c. Liquid laser
  • d. Semiconductor laser

111. ___ means that the characteristics and performance of an antenna are the same whether the antenna is radiating or intercepting an electromagnetic signal.

  • a. Antenna reciprocity
  • b. Antenna grounding
  • c. Antenna polarization
  • d. None of the above

112. Calculate the gain (relative to an isotropic) of a parabolic antenna that has a diameter of 3 m, an efficiency of 60% and operates at a frequency of 4 GHz.

  • a. 39.8 dBi
  • b. -18.1 dBi
  • c. 75.3 dBi
  • d. -43.8 dBi

113. A dipole antenna has a radiation resistance of 67 ohms and a loss resistance of 5 ohms, measured at the feed point. Calculate the efficiency.

  • a. 90%
  • b. 93%
  • c. 92%
  • d. 94%

114. An antenna’s beamwidth is measured __

  • a. Between half-power points
  • b. From front to back
  • c. Between the minor sidelobes
  • d. From +90 to -90 degrees

115. “ground effects” refers to the effects on an antenna’s radiation pattern caused by:

  • a. Radio signals reflecting off the ground
  • b. Buildings and other structures on the ground
  • c. Fading
  • d. Faulty connection of the feed cable ground

116. An antenna can be matched to a feed line using

  • a. A shorted stub
  • b. An LC network
  • c. A loading coil
  • d. All of the above

117. As the length of a “long-wire” antenna is increased, ___.

  • a. The number of lobes increases
  • b. The efficiency decreases
  • c. The number of nodes decreases
  • d. None of the above

118. It is the receiving antenna with a built-in preamplifier

  • a. Passive antenna
  • b. Active antenna
  • c. Coil antenna
  • d. LC antenna

119. Antennas that transmit an equal amount of energy in the horizontal direction are called __

  • a. Bidirectional
  • b. unidirectional
  • c. Omnidirectional
  • d. Unilateral

120. The ability of an antenna to send or receive signals over a narrow horizontal directional range is referred to as:

  • a. Focal factor
  • b. Directivity
  • c. Permittivity
  • d. Horizontal range

121. A basic antenna connected to a transmission line plus one or more additional conductors that are not connected to the transmission line form a:

  • a. Parasitic antenna
  • b. Bidirectional array
  • c. Half-wave antenna
  • d. Counterpoise

122. An antenna made up of a driven element and one or more parasitic elements is generally referred to as a ___.

  • a. Hertz antenna
  • b. Marconi antenna
  • c. Yagi antenna
  • d. Collinear antenna

123. Which antennas usually consist of two or more half-wave dipoles mounted end to end?

  • a. Yagi antenna
  • b. Collinear antenna
  • c. Hertz antenna
  • d. Marconi antenna

124. A stacked collinear antenna consisting of half wave dipoles spaced from one another by one-half wavelengths is the _.

  • a. End-fire antenna
  • b. Parasitic antenna
  • c. Wide bandwidth antenna
  • d. Broadside antenna

125. When the characteristic impedance of the transmission line matched the impedance of the transmitter and the impedance of the antenna itself

  • a. The SWR will be 10:1
  • b. Minimum power will take place
  • c. The SWR will be 1:10
  • d. Maximum power will take place

126. A one-quarter wavelength of coaxial or balanced transmission line of specific impedance connected between a load and a source in order to match impedance is:

  • a. A balun
  • b. An autotransformer
  • c. A Q section
  • d. None of the above

127. By how much should two antennas be separated for space diversity in the 15 GHz band?

  • a. 4 m
  • b. 5 m
  • c. 6 m
  • d. 7 m

128. How far from the transmitter could a signal be received if the transmitting and receiving antennas are 40 m and 22 m, respectively, above level terrain.

  • a. 49.22 km
  • b. 16.98 km
  • c. 45.22 m
  • d. 16.98 m

129. A signal propagates in a waveguide has a full wave of electric intensity change between the two further walls, and no component of the electric field in the direction of propagation, the mode of the waveguide is:

  • a. TE1,1
  • b. TE1,0
  • c. TE2,0
  • d. TE2,1

130. It is a microwave device that allows RF energy to pass in one direction with very little loss, but absorbs RF power in the opposite direction.

  • a. Circulator
  • b. Resonator
  • c. Isolator
  • d. Wave trap

131. A metal wrapped around the parabolic antenna aperture to eliminate sidelobes interfering nearby stations is called __.

  • a. Radome
  • b. Shroud
  • c. Shield
  • d. Bass drum

132. The wavelength of a wave in a waveguide

  • a. Is greater than in free space
  • b. Depends only on the waveguide dimensions and the free space wavelengths
  • c. Is inversely proportional to the phase velocity
  • d. Is directly proportional to the group velocity

133. Geostationary satellites are located at ___ with respect to the equator.

  • a. 0 deg latitude
  • b. 45 deg latitude
  • c. 0 deg longitude
  • d. 45 deg longitude

134. The quality of a space-link is measured in terms of ___ ratio.

  • a. S/N
  • b. C/N
  • c. G/T
  • d. EIRP

135. Why does the downlink frequency appear to vary by several kHz during a low earth orbit satellite pass?

  • a. The distance between the satellite and ground station is changing, causing the Kepler effect.
  • b. The distance between the satellite and ground station is changing, causing the Bernoulli effect.
  • c. The distance between the satellite and ground station is changing, causing the Boyle’s law effect.
  • d. The distance between the satellite and ground station is changing, causing the Doppler effect.

136. The most ambitious LEO constellation to date is:

  • a. Teledesic
  • b. Globalstar
  • c. NAVSTAR
  • d. Iridium

137. A satellite-dish owner has a 3 meter dish designed for C-Band (4 GHz) operation. The owner wants to use the same dish with a new feed horn, for Ku-Band 12 GHz) satellites. What effect will the change in frequency have on the gain and beamwidth of the antenna?

  • a. Gain increases by 9.54 dB, beamwidth decreases to 1.3 of its former value.
  • b. Gain decreases by 9.54 dB, beamwidth decreases to 1.3 of its former value.
  • c. Gain increases by 9.54 dB, beamwidth increases to 1.3 of its former value.
  • d. Gain increases by 9.54 dB, beamwidth increases to 1.3 of its former value.

138. The moon orbits the earth with a period of approximately 28 days. How far away is it? Assume circular orbit.

  • a. 380 Mm
  • b. 382 Mm
  • c. 384 Mm
  • d. 386 Mm

139. What is the length of the path to a geostationary satellite from an Earth station if the angle of elevation is 30 degrees?

  • a. 6400 km
  • b. 36000 km
  • c. 39000 km
  • d. 42400 km

140. What is the nominal uplink frequency for Ku Band?

  • a. 14 MHz
  • b. 12 MHz
  • c. 14 GHz
  • d. 12 GHz

141. To cover all inhabited regions of the earth, the number of polar-orbit satellite required is __.

  • a. 1
  • b. 2
  • c. 3
  • d. 4

142. What is the phase velocity of a rectangular waveguide with a dimension of 6 cm by 4 cm, desired operating frequency of 6 GHz and operates in TE11 mode? (Erroneous)

  • a. 5.43x10^8 m/s
  • b. 6.02x10^8 m/s
  • c. 3.31x10^8 m/s
  • d. 4.69x10^8 m/s

143. The highest frequency that can be used for skywave propagation between two specific points on earth’s surface.

  • a. Critical frequency
  • b. Cut-off frequency
  • c. Maximum usable frequency
  • d. Mid frequency

144. It is the height above Earth’s surface from which a refracted wave appears to have been reflected. It is the maximum height that this hypothetical reflected wave would have reached.

  • a. Virtual height
  • b. Actual height
  • c. Average height
  • d. Mean height

145. The height above mean sea level of a satellite in a geosynchronous orbit around Earth is:

  • a. 35,786 miles
  • b. 35,768 miles
  • c. 35,786 kilometers
  • d. 35,768 kilometers

146. A point in the orbit of an object orbiting the earth that is located closest to Earth.

  • a. Apogee
  • b. Perigee
  • c. Perihelion
  • d. Sub-satellite orbit

147. Find the velocity of a satellite in a circular orbit 500 km above the earth’s surface.

  • a. 7.61 km/s
  • b. 7.61 m/s
  • c. 761 m/s
  • d. 761 km/s

148. The outline of a communications satellite antenna pattern on the earth is known as:

  • a. Beam
  • b. Spot
  • c. Propagation pattern
  • d. Footprint

149. An earth station look angle is determined by:

  • a. Azimuth and elevation
  • b. Latitude and longitude
  • c. Bearing
  • d. True north

150. An ITU radiocommunications standard for satellite services which provides information on the range of frequencies that can be used by fixed satellite service systems for emergency and disaster relief operations.

  • a. ITU-R M1854
  • b. ITU-R 2009
  • c. ITU-R S.1001-2
  • d. ITU R S.004

Complete List of MCQs in Communications Engineering per topic


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