WorksheetsTransmission Line
Total questions: 50
Worksheet time: 48mins
Calculate the minimum length of a line conductor using Teflon as dielectric material with 2.3 as relative permittivity operating at 1Mcycles to be considered as a transmission line.
19.8 m
17.6 m
18.9 m
16.7 m
The reason that an RF transmission line should be matched at the transmitter end is to:
Prevent frequency drift
Overcome fading of the transmitted signal
Ensure radiated signal has intended polarization
Transfer maximum amount of power to the antenna
If the antenna is correctly matched to a transmitter, the length of transmission line
Must be an even number of half-waves
Will have no effect on the matching
Must be an odd number of quarter wave
Must be a full wavelength long
To obtain efficient power transmission from a transmitter to an antenna requires:
Inductive impedance
High load impedance
Matching of impedances
Low ohmic impedance
When analyzing a transmission line, its inductance and capacitance are considered to be:
lumped
distributed
Equal reactances
Ideal elements
A transmission line operating at 1.18 Mcycles is cut 60° from the load. Transmission line length in inches:
1,666.7 in
1,777.8 in
1,888.9 in
1,555.6 in
A lossless transmission line using air as dielectric material has an inductance of 625 nH/m and capacitance of 40 pF/ft. Calculate the velocity of propagation in megameters per second.
114.20
120.14
110.42
140.12
For a given length of RG 8A/U coaxial cable with a distributed capacitance of 96.6 pF/m, a distributed inductance of 241.56 nH/m, and a relative dielectric constant of 2.3, determine the velocity factor.
0.90
0.81
0.69
0.66
The velocity of propagation on a transmission line is controlled by which of the following line characteristics?
Conductance
Inductance only
Capacitance only
Capacitance & Inductance
Find the inductance of a 5-meter length transmission line if the characteristic impedance is 52 ohms and the capacitance is 75 pF/m.
1.015 H
1.015 mH
1.015 μH
1.015 nH
A 50-ohm transmission line with 75% velocity of propagation is operating at 52 MHz. Calculate for the series inductance per meter and shunt capacitance per meter of a given transmission line.
222.28 nH/m;88.91 pF/m
282.22 nH/m;89.18 pF/m
222.28 μH/m;88.91 nF/m
282.22 μH/m;89.18 nF/m
In what values are RF feed line losses expressed?
dB per unit length
ohms per meter
ohms per MHz
dB per MHz
As frequency increases, the resistance of the wire:
decreases
increases
stays the same
changes periodically
The characteristic impedance of a transmission line is determined by:
Its operating frequency
The signal applied at the input terminal
Its length
Its physical size and arrangement
Which of the following is not a common transmission line impedance?
50 ohms
75 ohms
20 ohms
300 ohms
A loss-free line transmission line has an inductance of 263.2 nH/m and a capacitance of 46.8 pF/m. If the generator produces a sinusoidal voltage at 3 MHz of 2V peak, determine the phase change if the line is 3 meter long.
11.34 deg
10.34 deg
12.34 deg
13.34 deg
What happens to the shunt capacitance of a parallel-wire transmission line if the conductors are moved farther apart?
increases
constant
decreases
Not enough info
The characteristic impedance of a 15-meter length of transmission line is 75 ohms. If 7.5 meters were cut off, the impedance would be:
75 Ω
37.5 Ω
150 Ω
100 Ω
A transmission line has a characteristic impedance of 50 Ωand a distributed resistance of 0.1 Ω/m. If the line is distortionless, determine the attenuation constant in Np/m.
0.014
0.002
0.020
0.140
In a distortionless coaxial cable, the value of series resistance and shunt capacitance values are doubled, then the values of attenuation constant and phase constant ________ and _______ respectively.
halves, doubles
quadruple, halves
doubles, doubles
doubles, halves
What is the characteristic impedance of an open wire line with conductors 4 mm in diameter separated by 15 mm?
252.41 Ω
241.52 Ω
421.52 Ω
452.21 Ω
What is the characteristic impedance of a coaxial cable using a solid polyethylene dielectric, an inner conductor of 1 mm diameter and an outer conductor of diameter 5 mm?
69.8 Ω
68.9 Ω
66.3 Ω
63.6 Ω
Calculate the time delay in nanosecond introduced by a 100 ft coaxial cable with a dielectric constant of 2.3
113.54
135.41
145.31
154.13
TDR equipment receives the signal 250 ns after the test signal had been transmitted. If the discontinuity of the line is found 35 meter from the test point, what is the velocity factor of the line?
0.993
0.933
0.339
0.399
Using TDR, a transmission line impairment is located 2000m from the source. For a velocity of propagation of 0.9c, determine the elapsed time from the beginning of the pulse to reception of the echo.
16.77 μs
13.75 μs
15.62 μs
14.81 μs
A time-domain reflectometer is commonly used to:
Measure the characteristic impedance of a cable
Replace a slotted-line
Find the position of a defect in a cable
All of the mentioned
In transmission lines, whenever current flows through one of these conductors, some energy is dissipated in the form of heat. This heat loss is a power loss and referred to as _______.
Copper loss
Induction loss
Radiation loss
Dielectric loss
This refers to a loss in transmission line that results from the heating effect on the insulation between the conductors.
Radiation loss
Copper loss
Dielectric loss
Induction loss
This refers to a loss in transmission line that occurs when the electromagnetic field about a conductor cuts through any nearby metallic object.
Copper loss
Induction loss
Radiation loss
Dielectric loss
This refers to a loss in transmission line that occurs because some magnetic lines of force about a conductor do not return to the conductor when the cycle alternates
Radiation loss
Dielectric loss
Copper loss
Induction loss
If the load impedance is equal to line characteristic impedance, which of the following can you can observe?
There is maximum power transfer
The standing wave ratio is equal to 1
The reflection coefficient is zero
All of the given choices can be observed
When sending power down a transmission line, it is usually desirable that as much power as possible will be absorbed by the load and as little as possible will be reflected back to the source. A negative voltage pulse sent down a transmission line terminated with its characteristic impedance:
Would reflect as a positive pulse
Would reflect as a positive pulse followed by a negative pulse
Would reflect as a negative pulse
Would not reflect at all
A positive voltage pulse sent down a transmission line terminated in a short-circuit:
Would reflect as a positive pulse followed by a negative pulse
Would reflect as a positive pulse
Would reflect as a negative pulse
Would not reflect at all
The most desirable reflection coefficient is:
infinity
0.5
1
0
On a transmission line, reflections begin at which of the following locations?
load
middle
source
half-wavelength point
A 75-ohm lossless line is terminated in error with a 93-ohm resistor. A generator sends 100 mW down the line. What is the reflection coefficient?
0.0107
0.178
0.115
0.199
If the characteristic impedance of the feedline does not match the antenna input impedance, then:
The antenna will not radiate any signal
The SWR reading falls to 1:1
Standing waves are produced in the feedline
Heat is produced at the junction
What does an SWR reading of 1:1 mean?
No power is going to the antenna
The SWR meter is broken
An antenna for another frequency band is probably connected
The best impedance match has been matched
The forward power in a transmission line is 150 W and the reverse power is 20 W. Calculate the SWR on the line.
3.15
1.15
4.15
2.15
Determine the standing wave ratio of a 300-ohm line whose load is 400 + j150 ohms.
1.67
2.67
3.67
4.67
What proportion of incident power is reflected back from the load for a 75-ohm line terminated with 50 - j25 ohms?
6.84%
7.84%
5.84%
8.84%
A transmitter supplies 20 W to load through line with SWR of 2. The power absorbed by the load:
17.6 W
16.7 W
18.7 W
17.8 W
If the length of an open-circuited stub is less than quarter-wavelength but greater than 0, the stub behaves as:
inductor
complex
resistor
capacitor
A shorted half-wave line at the operating frequency acts like a(n):
Capacitor
Inductor
Parallel resonant circuit
Series resonant circuit
Which of the following sections of transmission line can be used as a parallel resonant circuit?
A shorted 1/2-wavelength section
An open 3/4-wavelength section
A shorted 1/4-wavelength section
An open 1/4-wavelength section
Which of the following ratios samples the magnetic field along the line?
PSWR
VSWR
ISWR
RSWR
A 75-ohm transmission line could be matched to the 300-ohm feedpoint of an antenna:
By using a 4 to 1 balun
By using a 4 to 1 trigatron
By inserting a diode in one leg of the antenna
With an extra 250 ohm resistor
What would be the approximate series impedance of a quarter-wave matching line used to match a 600 ohms feed to 70 ohms antenna?
405 Ω
305 Ω
105 Ω
205 Ω
In a twin-wire transmission line in air, the adjacent voltage maxima are at 12.5 cm and 27.5 cm. The operating frequency is A. 1 GHz B. 4 GHz C. 2 GHz D. 3 GHz
1 GHz
4GHz
2GHz
3GHz
A 75-ohm characteristic impedance transmission line is terminated by a load impedance of 120 ohms. Determine the input impedance looking into the line 1 meter long, if the line has a velocity factor of 0.9 and operates at a frequency of 50 MHz.
51.8-j18.4 ohm
12.2-j34.4 ohm
34.4-j12.2 ohm
18.4-j51.8 ohm
