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.

### Online Questions and Answers 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**

**MCQs from Number 1 – 50**Answer key:

**PART I**

**MCQs from Number 51 – 100**Answer key:

**PART II**

**MCQs from Number 101 – 150**Answer key:

**PART III**

**MCQs from Number 151 – 200**Answer key:

**PART IV**

**MCQs from Number 201 – 250**Answer key:

**PART V**

**MCQs from Number 251 – 300**Answer key:

**PART VI**

**MCQs from Number 301 – 350**Answer key:

**PART VII**

**MCQs from Number 351 – 400**Answer key:

**PART VIII**

**MCQs from Number 401 – 450**Answer key:

**PART IX**

**MCQs from Number 451 – 500**Answer key:

**PART X**

### Continue Practice Exam Test Questions Part III 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

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

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

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

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

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

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

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

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

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

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

112. Emission designation for a facsimile.

- a. H3E and A4E
- b. R3E and A4E
- c. F4E and J3E
- d. F3C and A3E

113. Commonly used telephone wire.

- a. AWG #19
- b. AWG #18
- c. AWG #30
- d. AWG #33

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

- a. Frequency
- b. Hop
- c. Wavelength
- d. Crest

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

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

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

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

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

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

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

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

- a. bandwidth
- b. loss
- c. entropy
- d. quantum

123. The twists in twisted wire pairs

- a. reduced electromagnetic interference
- b. occur at a 30-degree angle
- c. eliminate loading
- d. were removed due to cost

124. An example of a bounded medium is

- a. coaxial cable
- b. waveguide
- c. fiber-optic cable
- d. all of the above

125. Loading means the addition of

- a. resistor
- b. capacitor
- c. bullet
- d. inductance

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

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

- a. length
- b. conductor diameter
- c. conductor spacing
- d. dielectric material

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

- a. 50 ohms
- b. 75 ohms
- c. 120 ohms
- d. 300 ohms

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

- a. Zo = ZL
- b. Zo > ZL
- c. Zo < ZL
- d. Zo = 0

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

- a. using LC matcging network
- b. adjusting antenna length
- c. using a balun
- d. adjusting the length of transmission line

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

- a. An electric field
- b. Radio waves
- c. Standing waves
- d. A magnetic field

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

- a. 0
- b. 1
- c. 2
- d. Infinity

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

134. What is the most desirable reflection coefficient?

- a. 0
- b. 0.5
- c. 1
- d. Infinity

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

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

137. One meter is one wavelength at a frequency of

- a. 150 MHz
- b. 164 MHz
- c. 300 MHz
- d. 328 MHz

138. At very high frequencies, transmission lines act as

- a. Tuned circuits
- b. Antennas
- c. Insulators
- d. Resistors

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

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

141. A medium least susceptible to noise?

- a. Shielded pair
- b. Twisted pair
- c. Fiber-optic
- d. Coaxial

142. A medium most widely used in LANs?

- a. Parallel-wire line
- b. Twisted pair
- c. Fiber-optic cable
- d. Coaxial

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

- a. Parallel-wire line
- b. Coaxial cable
- c. Waveguide
- d. Open-wire ceramic supports

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

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

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

- a. Adjacent channel interference
- b. Ghost
- c. Co-channel interference
- d. Crosstalk

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

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

- a. -40db
- b. 40db
- c. 40dBm
- d. -4dBm

149. Important useful quantities describing waveforms.

- a. Time and frequency
- b. Voltage and current
- c. Frequency and voltage
- d. Power and frequency

150. Halving the power means

- a. 6-dB gain
- b. 3-dB loss
- c. 3-dB gain
- d. 6-dB loss