Transmission Lines
1. What is the impedance of two sections of quarterwave transformer (connected in series) needed in order
to match a line 54 Ω to a load of 300 Ω
A. 28.9 Ω, 958.4 Ω
B. 82.9 Ω, 195.4 Ω
C. 8.9 Ω, 15.4 Ω
D. 182.9 Ω, 295.4 Ω
3. A transmitter is required to deliver 100 W to an
antenna through 45 m of coaxial cable with a loss of 4
dB/100m. What must be the output power of the
transmitter, assuming the line is matched?
9. A transmission line of unknown impedance is
terminated with two different resistances, and the SWR
is measured each time. With a 75 Ω termination, the
SWR measures 1.5. With a 300 Ω termination, it
measures 2.67. What is the impedance of the line
A. 1.12 Ω
B. 32 Ω
C. 50 Ω
D. 112 Ω
A. 34.51 W
11. A 10 V positive going pulse is sent down a 50 m of
lossless 50 Ω cable with a velocity factor of 0.8. The
cable is terminated with a 150Ω resistor. Calculate the
length of time it will take the reflected pulse to return
to the start and the amplitude of the reflected pulse.
B. 345 W
A. 381 ns, 7.5 V
C. 1.51 W
B. 587 ns, 6 V
D. 151 W
C. 417 ns, 5 V
D. 256 ns, 12 V
5. A TDR display shows a discontinuity 1.4 μs from the
start. If the line has a velocity factor of 0.8 how far is the
fault from the reflectometer?
A. 16.8 m
B. 168 m
C. 32.5 m
D. 325 m
13. A transmitter delivers 50 W into a 600 Ω lossless line
that is terminated with an antenna that has an
impedance of 275 Ω, resistive. How much power
actually reaches the antenna?
A. 43.1 W
B. 10.71 W
C. 22.42 W
7. The forward power in a transmission line is 150 W,
and the reverse power is 20 W. Calculate the SWR on
the line.
A. 0.55
B. -1.6
C. 2.15
D. 0.15
D. 38.43 W
15. A properly matched transmission line has a loss of
1.5 dB/m. If 10 W is supplied to one end of the line, how
many watts reach the load, 27 m away?
A. 9.8 W
B. 6.1 W
C. 7.8 W
D. 9.1 W
17. Calculate the impedance looking into a 50 Ω line 1 m
long, terminated in a load impedance of 100 Ω, if the
line has velocity factor of 0.8 and operates at a
frequency of 30 MHz.
B. 0.493 dB/m
C. 0.568 dB/m
D. 0.0493 dB/m
A. 10 – j50 Ω
B. 40 - j30 Ω
C. 30 – j60 Ω
D. 20 – j40 Ω
27. On a Smith Chart, you "normalize" the impedance
by:
A. assuming it to be zero
B. dividing it by 2π
19. A coaxial cable has a capacitance of 90 pF/m and a
characteristic impedance of 50 Ω. Find the inductance
of a 1 m length.
A. 225 nH/m
B. 22.5 nH/m
C. 2.25 nH/m
D. 225 pH/m
C. multiplying it by 2π
D. dividing it by Z0
29. The velocity factor of a cable depends mostly on:
A. the wire resistance
B. the dielectric constant
C. the inductance per foot
D. dimension of the line
21. As frequency increases, the resistance of a wire:
A. increases
B. decreases
C. stays the same
D. changes periodically
31. In ferrite, what does YIG mean?
A. Yttrium-Immense-Garnet
B. Yttrium-Iron-Garnet
C. Yttrium-Iron-Gold
D. Yttrium-Immense-Gold
23. The attenuation coefficient of a line is 0.0006 N/m.
Determine the attenuation coefficient in dB/m
B. 0.521 dB/m
33. For a shorted load TL, the value of reflection
coefficient and standing wave ratio is _____, _____
respectively.
C. 0.00521 dB/m
A. -1, ∝
D. 5.21 dB/m
B. 0, -1
A. 0.0521 dB/m
C. ∝, 1
25. The primary line constant for a coaxial cable at a
frequency of 10 MHz were determine approximately as;
L = 234 nH/m, C = 93.5 pF/m, R = 0.568 Ω/m, G = 0
Calculate the attenuation coefficient in dB/m.
A. 0.00568 dB/m
D. -1, 0
35. Determine the magnitude of the reflected voltage if
a 10 V signal is applied to a 50 Ω coaxial transmission
line terminated in a 200 Ω load.
C. as large as possible
D. there is no optimum value
A. 8V
C. 7.5V
45. Calculate the velocity factor for a transmission line
with a series inductance of 280 nH/m and a shunt
capacitance of 82.5 pF/m
D. 12V
A. 1.24
B. 6V
B. 1.42
37. RG-59U, a common type of transmission line for
microwave applications, has an open circuit impedance
of 150∠25° Ω and a short circuit impedance of 37.5∠25°
Ω. What is the characteristic impedance of the line?
C. 0.693
A. 55∠-35° Ω
47. A non-optimum value for SWR will cause:
B. 35∠-15° Ω
A. standing waves
C. 95∠-55° Ω
B. loss of power to load
D. 75∠-5° Ω
C. higher voltage peaks on cable
D. 0.936
D. all of the above
39. Find the impedance on a 50 Ω transmission line at a
distance of λ/8 from a 400 Ω load.
A. 130∠-51° Ω
B. 350∠-81° Ω
C. 950∠-83° Ω
D. 50∠-76° Ω
49. Calculate the characteristic impedance of a line with
a shunt capacitance of 95 pF/m and having a dielectric
medium with a 1.55 index of refraction
A. 72.38 Ω
B. 54.38 Ω
C. 64.8 Ω
41. The effect of frequency on the resistance of a wire is
called:
A. I 2 R loss
D. 74 Ω
C. the skin effect
51. Determine the amount of distributed resistance of a
15-m coaxial cable with a total capacitance of 1.4025
nF, total inductance of 3.51 μH and total attenuation of
0.7395 dB
D. the flywheel effect
A. 0.569 Ω/m
B. the Ohmic effect
B. 5.69 Ω/m
43. The optimum value for SWR is:
C. 569 Ω/m
A. zero
D. 56.9 Ω/m
B. one
53. Calculate the amount of phase shift coefficient in
rad/m for a line with a velocity factor of 0.85 and
operating at 12 MHz.
C. 9.08 cm
D. 90.8 cm
A. 0.296 rad/m
B. 29.6 rad/m
C. 296 rad/m
D. 2.96 rad/m
63. For an open load TL, the value of return loss and
reflection coefficient is _____, _____ respectively.
A. -1, ∝
B. 1, 1
C. -1, 1
55. A positive voltage pulse sent down a transmission
line terminated with its characteristic impedance:
D. ∝, -1
A. would reflect as a positive pulse
B. would reflect as a negative pulse
65. A GUNN device has a thickness of 7 μm. At what
frequency will it oscillate in the transit-time mode?
C. would reflect as a positive pulse followed by a
negative pulse
A. 1.3 GHz
D. would not reflect at all
B. 1.43 GHz
C. 14.3 GHz
57. What is the equivalent capacitance for a 50 Ω shotcircuited line 3λ/8 in length at 500 MHz?
A. 56 pF
D. 143 GHz
C. 6.4 pF
67. A microstrip line is formed using a 0.095-in thick PC
board (εr=1.8) with a bottom groundplane and a single
0.15-in wide, 0.008-in thick track on the top. What is the
characteristic impedance?
D. 23.5 pF
A. 112.14 Ω
B. 90.2 pF
B. 72.4 Ω
59. Find the characteristic impedance of the waveguide
if the cut-off frequency is 3.75 GHz and will operate at
5GHz.
C. 85.34 Ω
D. 66.8 Ω
A. 50 Ω
B. 570 Ω
C. 5.7 Ω
D. 57 Ω
69. Calculate the group and phase velocities for an angle
of incidence of 33°
A. 1.6x108 m/s, 5.51x108 m/s
B. 2.8x108 m/s, 3.2x108 m/s
C. 5.51x108 m/s , 1.6x108 m/s
61. Calculate the guide wavelength for the waveguide
whose cut-off is 3.75 GHz and operates at 5 GHz.
A. 98 cm
B. 908 cm
D. 3.2x108 m/s , 2.8x108 m/s
71. A waveguide with a 4.5 GHz cut-off frequency is
excited with a 6.7 GHz signal. Find the wavelength in
free space, and the wavelength in the waveguide.
C. Resistive impedance
D. An inductive impedance
A. 0.716 m, 0.224 m
C. 0.448 m, 0.136 m
81. What are the minimum and maximum combined
VSWR limits at an interface characterized by a 1.25:1
VSWR and a 2.00:1 VSWR?
D. 0.224 m, 0.716 m
A. 3.75:1 (min), 1.25:1 (max)
B. 0.136 m, 0.448 m
B. 1.60:1 (min), 2.50:1 (max)
73. A 50-Ω short circuited line is 0.1λ in length, at a
frequency of 500 MHz. Calculate the equivalent
inductance.
C. 0.75:1 (min), 3.25:1 (max)
D. 1.75:1 (min), 2.25:1 (max)
A. 24.5 nH
C. 245 nH
83. While we're on the subject of Smith charts, what is
the impedance of the point at the far right edge of the
center horizontal line?
D. 2.45 nH
A. 0 - j50 Ω
B. 0.245 nH
B. 50 ± j0 Ω
75. At very high frequencies, transmission lines are used
as
C. 0 ± j0 Ω
D. 0 ± j∞ Ω
A. Antennas
B. Resistors
C. Insulators
85. What happens to the noise figure of a receiver when
a 10 dB attenuator is added at the input?
D. Tuned circuits
A. Noise figure increases by 10 dB
B. Noise figure doesn't change
77. While we're on the subject of Smith charts, what is
the impedance of the point at the dead center line?
C. Noise figure decreases by 10 dB
D. All of the above
A. 0 - j50 Ω
B. 50 ± j0 Ω
C. 0 ± j0 Ω
87. What is the impedance seen at the input when the
transmission line is shorted?
D. 0 ± j∞ Ω
A. jZo tan( ) βA
B. −jZo cot( ) βA
79. On a Smith chart, what does a point in the bottom
half of the chart represent?
A. A capacitive impedance
B. Power saturation
C. 0
D. ∞
89. The forward-progress velocity of the wavefront in a
waveguide is called as ______.
99. What is the main reason why coaxial cable is not
used in microwave signal transmission?
A. Velocity of propagation
A. Number of repeaters
B. Phase velocity
B. High attenuation
C. Wave velocity
C. Wide bandwidth
D. Group velocity
D. Low impedance
91. A standing wave ratio is a measure of
101. An electronic equipment used in radio
communications to measure standing wave ratio
A. power out compared to noise out
B. the amount of power received
C. power radiated from the surface
D. power out compared to reflected power back
A. Oscilloscope
B. Reflectometer
C. Wave meter
D. Radio meter
93. An SWR reading which has a short circuit
termination.
A. One
B. Infinity
C. Zero
D. Unstable
103. Referred as the dielectric constant of a
transmission line material
A. Inductance and capacitance
B. Propagation velocity
C. Characteristic impedance
D. Velocity factor
95. Which of the following term is used to describe the
attenuation and phase shift per unit length of a
transmission line?
A. Propagation constant
B. Degree of shift
C. Phase shift
D. Line constant
105. What is the input impedance equivalent of an open
ended transmission line which is longer than a quarter
wavelength?
A. Equivalent to reactive circuit
B. As pure inductor
C. As resistive equivalent
D. Open equivalent
97. Energy that has neither been radiated into space nor
completely transmitted
A. Modulated waves
B. Captured waves
C. Standing waves
D. Incident waves
107. The greater the diameter of a wire, the _____ is
the resistance.
A. unstable
B. lesser
A. Velocity factor
B. Characteristic impedance
C. Standing wave ratio
D. Surge impedance
C. stable
D. higher
109. Technical study which deals with production,
transport and delivery of a quality signal from source to
destination
A. Communication System Engineering
B. Telephony Engineering
117. In a transmission line, if the maximum current to
minimum current ratio is 2:1 what is the ratio of the
maximum voltage?
A. 1:2
B. 2:1
C. 4:1
D. 1:4
C. Telegraphic Engineering
D. Transmission System Engineering
119. Transmission line must be matched to the load to
A. transfer maximum power to the load
111. What is the meaning of the term velocity factor of
a transmission line?
A. The velocity of the wave on the transmission line
multiplied by the velocity of light in vacuum
B. reduce the load current
C. transfer maximum current to the load
D. transfer maximum voltage to the load
B. The index of shielding for coaxial cable
C. The ratio of the characteristic impedance of the line
to the terminating impedance
121. Which of the following determine the
characteristic of a transmission line?
D. The velocity of the wave on the transmission line
divided by the velocity of the light in a vacuum
A. Physical dimensions
B. Capacitance
C. Length
113. Best reason for pressurizing waveguides with dry
air
D. Inductance
A. To reduce the possibility of internal arcing
C. To increase the speed of propagation
123. Characteristic impedance of a transmission line is
the impedance measured at the ______when its length
is infinite.
D. To maintain propagation
A. output
B. To maintain temperature of the waveguide
B. shorted end of the line
115. What is the term for the ratio of actual velocity at
which a signal travels through a line to the speed of
light in a vacuum?
C. midsection
D. input
125. Transmission lines when connected to antenna
have
A. resistive load whose resistance is greater than the
characteristic impedance of the line
B. resistive load whose resistance is less than
characteristic impedance
C. resistive load at the resonant frequency
D. capacitive load
127. Transmission lines are either balanced or
unbalanced will respect to
A. positive terminal
B. input
C. ground
D. negative terminal
129. Propagation mode of microwave in a waveguide is
known as
A. TM
B. SW
C. TEM
D. TE