# MCQ in Transmission Fundamentals Part 3 | ECE Board Exam

(Last Updated On: May 6, 2020) This is the Multiples Choice Questions Part 3 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 3 of the Series

101. The frequency range over which a rectangular waveguide is excited in the dominant mode is limited to

a. the difference between the frequency for which the reflection angle is 90o and the frequency for which angle is zero

b. the difference between the frequency for which the free-space wavelength is equal to the cutoff value and the frequency for which the free-space wavelength is equal to the guide wavelength

c. the difference between the frequency at which the cutoff wavelength is twice the narrow dimension

d. none of these

Solution:

102. If a rectangular waveguide is to be excited in the dominant mode, the E-probe should be inserted

a. at the sealed end

b. at a distance of one quarter –wavelength from the sealed end

c. at a distance of one-half wavelength from the sealed end

d. at a distance of three-quarters of a wavelength from the sealed end

Solution:

103. A quarter-wave line is connected to an RF generator and is shorted out at the far end. What is the input impedance to the line generator?

a. A low value of resistance

b. A high value of resistance

c. A capacitive resistance which is equal in the value to the line’s surge impedance

d. An inductive resistance which is equal to the value to the line’s surge impedance

Solution:

104. If the SWR on a transmission line has a high value, the reason could be

a. an impedance mismatch between the line and the load

b. that the line is non-resonant

c. a reflection coefficient of zero at the load

d. that the load is matched to the line

Solution:

105. If a quarter-wave transmission line is shorted at one end

a. there is minimum current at the shorted end

b. the line behaves as a parallel-tuned circuit in relation to the generator

c. the line behaves as a series-tuned circuit in relation to the generator

d. there is a minimum voltage at the shorted end

Solution:

106. A 50-ohm transmission line is feeding an antenna which represents a 50 ohm resistive load. To shorten the line, the length must be

a. any convenient value

b. an odd multiple of three quarters of a wavelength

c. an odd multiple of half a wavelength

d. an even multiple of a quarter of a wavelength

Solution:

107. The outer conductor of the coaxial cable is usually grounded

a. at the beginning and at the end of the cable

b. only at the beginning of the cable and only at the end of the cable

c. only at the end of the cable

d. at the middle of the cable

Solution:

108. A feature of an infinite transmission line is that

a. its input impedance at the generator is equal to the line’s surge impedance

b. its phase velocity is greater than the velocity of light

c. no RF current will be drawn from the generator

d. the impedance varies at different positions on the line

Solution:

109. When the surge impedance of a line is matched to a load, the line will

a. transfer maximum current to the load

b. transfer maximum voltage to the load

c. transfer maximum power to the load

d. have a VSWR equal to zero

Solution:

110. A lossless line is terminated by a resistive load which is not equal to the surge impedance. If the value of the reflection coefficient is 0.5, the VSWR is

a. 2

b. 3

c. 4

d. 15

Solution:

111. Ratio of the mismatch between the antenna and the transmitter power.

a. Standing wave pattern

b. Reflection coefficient

c. SWR

d. Index of refraction

Solution:

112. Emission designation for a facsimile.

a. H3E and A4E

b. R3E and A4E

c. F4E and J3E

d. F3C and A3E

Solution:

113. Commonly used telephone wire.

a. AWG #19

b. AWG #18

c. AWG #30

d. AWG #33

Solution:

114. What is the distance traveled by a wave in the time of one cycle?

a. Frequency

b. Hop

c. Wavelength

d. Crest

Solution:

115. The velocity factor is inversely proportional with respect to the _______.

a. square of the dielectric constant

b. square root of the dielectric constant

c. dielectric current

d. square root of refractive index

Solution:

116. ________ is a hollow structure that has no center conductor but allows waves to propagate down its length.

a. Waveguide

b. Hybrid

c. Pipe

d. Directional coupler

Solution:

117. To connect a coaxial line to a parallel wire line, _______ is used.

a. hybrid circuit

b. balun

c. directional coupler

d. quarter-wave transformer matching circuit

Solution:

118. What length for which the input power has been halved for a transmission line with an attenuation of 6 dB/km?

a. 1.5 km

b. 0.5 km

c. 63 km

d. 2 km

Solution:

119. Ina waveguide, _______ is a specific configuration of electric and magnetic fields that allows a wave to propagate.

a. set-up

b. coupler

c. channel

d. mode

Solution:

120. A rectangular waveguide has dimensions of 3 cm x 5 cm. What is the dominant mode cut-off frequency?

a. 2 GHz

b. 3 GHz

c. 2.5 GHz

d. 3.5 GHZ

Solution:

121. ________ are transmission lines which can convey electromagnetic waves only in higher order modes?

a. Coaxial cables

b. Twisted pairs of telephone wire

c. Power cables

d. Waveguides

Solution:

122. The amount of uncertainty in a system of symbols is also called

a. bandwidth

b. loss

c. entropy

d. quantum

Solution:

123. The twists in twisted wire pairs

a. reduced electromagnetic interference

b. occur at a 30-degree angle

d. were removed due to cost

Solution:

124. An example of a bounded medium is

a. coaxial cable

b. waveguide

c. fiber-optic cable

d. all of the above

Solution:

a. resistor

b. capacitor

c. bullet

d. inductance

Solution:

126. What is the most commonly used transmission line for high frequency application?

a. Two-wire balance line

b. Single wire

c. Three-wire line

d. Coaxial

Solution:

127. The characteristic impedance of a transmission line does not depend upon its

a. length

b. conductor diameter

c. conductor spacing

d. dielectric material

Solution:

128. One of the following is not a common transmission line impedance.

a. 50 ohms

b. 75 ohms

c. 120 ohms

d. 300 ohms

Solution:

129. For maximum absorption of power at the antenna, the relationship between the characteristic impedance of the line Zo and the load impedance ZL should be

a. Zo = ZL

b. Zo > ZL

Solution:

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130. The mismatch between antenna and transmission line impedance cannot be corrected for by

a. using LC matching network

c. using a balun

d. adjusting the length of transmission line

Solution:

131. ________ is a pattern of voltage and current variations along a transmission line not terminated in its characteristic impedance.

a. An electric field

c. Standing waves

d. A magnetic field

Solution:

132. Which is the desirable SWR on a transmission line?

a. 0

b. 1

c. 2

d. Infinity

Solution:

133. A 50ohm coax is connected to a 73-ohm antenna. What is the SWR?

a. 0.685

b. 1

c. 1.46

d. 2.92

Solution:

134. What is the most desirable reflection coefficient?

a. 0

b. 0.5

c. 1

d. Infinity

Solution:

135. What is the ratio expressing the percentage of incident voltage reflected on a transmission line?

a. Velocity factor

b. Standing-wave ratio

c. Reflection coefficient

d. Line efficiency

Solution:

136. The minimum voltage along a transmission line is 260 V, while the maximum is 390 V, the SWR is

a. 0.67

b. 1.0

c. 1.2

d. 1.5

Solution:

137. One meter is one wavelength at a frequency of

a. 150 MHz

b. 164 MHz

c. 300 MHz

d. 328 MHz

Solution:

138. At very high frequencies, transmission lines act as

a. Tuned circuits

b. Antennas

c. Insulators

d. Resistors

Solution:

139. A shorted quarter-wave line at the operating frequency acts like a/an

a. Capacitor

b. Inductor

c. Series resonant circuit

d. Parallel resonant circuit

Solution:

140. A shorted half-wave line at the operating frequency acts like a/an

a. Capacitor

b. Inductor

c. Series resonant circuit

d. Parallel resonant circuit

Solution:

141. A medium least susceptible to noise?

a. Shielded pair

b. Twisted pair

c. Fiber-optic

d. Coaxial

Solution:

142. A medium most widely used in LANs?

a. Parallel-wire line

b. Twisted pair

c. Fiber-optic cable

d. Coaxial

Solution:

143. The most commonly used transmission line in television system.

a. Parallel-wire line

b. Coaxial cable

c. Waveguide

d. Open-wire ceramic supports

Solution:

144. The impedance of a TV transmission line depends on several factors. Which is not one of those factors?

a. Diameter

b. Length of the wire

c. Dielectric material

d. Separation between conductors

Solution:

145. DC blocks are used in coaxial transmission line for the purpose of

a. passing DC while blocking AC

b. passing AC voltage but prevent DC

c. preventing AC voltage from reaching the pre-amplifier

d. preventing AC power supply voltage from being shorted by a balun or band splitter

Solution:

146. _______ is a type of interference caused by off-air TV channels 2 and 4, plus a satellite dish operating on channel 3.

b. Ghost

c. Co-channel interference

d. Crosstalk

Solution:

147. Dithering (in TVRO communication) is a process of

a. Reducing the effect of noise on the TVRO video signal

b. Centering the video fine tuning on TVRO channels

c. Moving the feedhorn rotor to the precise angle

d. Moving the actuator exactly onto the desired satellite beam

Solution:

148. A network that has an input of 75dB and an output of 35dB. The loss of the network is

a. -40 db

b. 40 db

c. 40 dBm

d. -4 dBm

Solution:

149. Important useful quantities describing waveforms.

a. Time and frequency

b. Voltage and current

c. Frequency and voltage

d. Power and frequency

Solution:

150. Halving the power means

a. 6-dB gain

b. 3-dB loss

c. 3-dB gain

d. 6-dB loss

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

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

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