TRANSMISSION LINES

A system of conductors used to convey electric power or signal between two or more points
a. Channels
b. Optical cables
c. Transmission lines
d. Waveguides

c. Transmission lines

These conductors are uniformly spaced by insulators. They have low losses at low and medium frequencies and are economical to construct and maintain
a. Coaxial cables
b. Open-wire transmission lines
c. Optical cables
d. Waveguides

b. Open-wire transmission lines

To prevent radiation losses and interference from external sources, the inner conductor of this transmission line is completely enclosed with a metal sheath or braid
a. Coaxial cables
b. Open-wire transmission line
c. Optical cables
d. Waveguides

a. Coaxial cables

The term “balanced line” means that
a. Both conductors carry currents that flow in opposite directions
b. Conductors present equal capacitance to ground
c. One conductor is connected to ground
d. A and B above

d. A and B above

The characteristic impedance of a transmission line is determined by:
a. Its operating frequency
b. Its length
c. Its physical size and arrangement
d. The signal applied at the input terminal

c. Its physical size and arrangement

The distributed parameters of the transmission line are: the series resistance; the series inductance; the shunt capacitance and the shunt conductance. What parameter was determined due to dielectric losses?
a. Series resistance
b. Series inductance
c. Shunt capacitance
d. Shunt conductance

d. Shunt conductance

Shunt capacitance was determined due to:
a. Conductors were close to each other
b. The length and diameter of the conductors
c. Dielectric losses
d. Flux linkage

a. Conductors were close to each other

Series resistance was determined due to:
a. Conductors were close to each other
b. The length and diameter of the conductors
c. Dielectric losses
d. Flux linkages

b. The length and diameter of the conductors

At radio frequencies, a line is considered lossless because:
a. Characteristic impedance is determined by its physical structure
b. Inductive reactance is much more than the resistance
c. Capacitive reactance is much larger than the shunt conductance
d. B and C above

d. B and C above

Determine the characteristic impedance of a transmission line which has a capacitance of 30pF/m and an inductance of 75nH/m
a. 5 Ω
b. 50 Ω
c. 500 Ω
d. 5 KΩ

b. 50 Ω

The Zo of an open-wire balanced line is determined from its physical structure. [Zo = 276 log(2S/d)]. At what condition is the Zo minimum?
a. S = d
b. S = 2d
c. d = 2S
d. S >> d

a. S = d

If a change in the dielectric material decreases the capacitance, the characteristic impedance is:
a. Kept constant
b. Decreased
c. Increased
d. Halved

c. Increased

All power applied at the input of the line will be absorbed by the load if:
a. Zo > ZL
b. Zo < ZL
c. ZL = Zo
d. Zo = ZL

c. ZL = Zo

When ZL ≠ Zo, the power sent down the line toward the load is called the:
a. Incident power
b. Reflected power
c. Power dissipation
d. Carrier power

a. Incident power

When mismatch is great, this power actually causes damage to the transmitter or the line itself.
a. Incident power
b. Reflected power
c. Power dissipation
d. Carrier power

b. Reflected power

A resultant wave due to the combination of incident and reflected wave
a. Electromagnetic wave
b. Sine wave
c. Standing wave
d. Current

c. Standing wave

If the load impedance matches the characteristic impedance of the line, there are _____ standing waves
a. More
b. Less
c. No
d. Ten (10)

c. No

A measure of the mismatch between line and load impedance is called
a. Reflection coefficient
b. Standing wave ratio
c. Loss
d. Standing waves

b. Standing wave ratio

At matched condition, SWR is equal to
a. Zero
b. One
c. 100
d. Infinite

b. One

The ratio of the reflected voltage to the incident voltage on the transmission line is termed as
a. Reflection coefficient
b. Standing wave ratio
c. Loss
d. Standing waves

a. Reflection coefficient

A shorted or opened line will have a reflection coefficient of
a. Zero
b. One
c. 100
d. Infinite

b. One

The minimum voltage along a transmission line is 260V, while the maximum voltage is 390V. The SWR is
a. 0.67
b. 1.0
c. 1.2
d. 1.5

d. 1.5

At UHF and microwave frequencies, transmission lines are commonly used as
a. Antenna
b. Coupler
c. Resonant circuit
d. Transformer

d. Transformer

The time required for a wave to propagate on a transmission line will depend on the value of its
a. Series resistance and shunt conductance
b. Series inductance and shunt capacitance
c. Series resistance and series inductance
d. Shunt conductance and shunt capacitance

b. Series inductance and shunt capacitance

The current (and voltage) distribution along a matched line vary _____ with distance
a. Linearly
b. Inversely
c. Exponentially
d. Logarithmically

c. Exponentially

A measure of how the voltage or current decreases with distance along the line
a. Propagation constant
b. Attenuation constant
c. Phase constant
d. SWR

b. Attenuation constant

The value remains constant for any length of wire
a. Characteristic impedance
b. Inductance
c. Capacitance
d. Propagation constant

a. Characteristic impedance

A measure of the difference in phase between the input and output current or voltage
a. Attenuation constant
b. Reflection constant
c. Phase constant
d. Characteristic impedance

c. Phase constant

To match a 300Ω transmission line to a 100Ω load, the impedance of the quarter-wave transformer is
a. 1.732 kΩ
b. 20 Ω
c. 200 Ω
d. 173.21 Ω

d. 173.21 Ω

An attenuation of 1 Neper is equal to _____ dB
a. 8.686 × 10⁻³
b. 8.686
c. 4.343
d. 0.115

b. 8.686

Characteristic impedance and load impedance must be matched in order to transfer
a. Maximum power to the load
b. Maximum current to the load
c. Maximum voltage to the load
d. Maximum standing waves

a. Maximum power to the load

The ratio of reflected voltage to the forward or incident voltage is termed as
a. Reflection coefficient
b. SWR
c. VSWR
d. Propagation constant

a. Reflection coefficient

A more common method of expressing the degree of mismatch between Zo and ZL is return loss. [Return Loss = 20 log (1/ reflection coefficient)]. Echoes may result if return loss is
a. Too high
b. Too low
c. Zero
d. Infinite

b. Too low

The points along the line where the incident and reflected voltages are in phase are points of
a. Maximum voltage and maximum current
b. Minimum voltage and minimum current
c. Maximum voltage and minimum current
d. Minimum voltage and maximum current

a. Maximum voltage and maximum current

When incident and reflected voltages are out of phase, the voltages are
a. Added
b. Neutralized
c. Multiplied
d. Divided

b. Neutralized

If the distance of separation between centers of two parallel wires is increased, the characteristic impedance will
a. Increased
b. Decreased
c. Be the same
d. Doubled

a. Increased

Which statement is true?
a. Increasing the length of the wire will increase the SWR
b. Decreasing the length of the wire will increase the SWR
c. Increasing the length of the wire will decrease the SWR
d. Changing the length of the wire will have no effect on the SWR

d. Changing the length of the wire will have no effect on the SWR

The characteristic impedance of balanced wire varies from
a. 150 to 600 Ω
b. 40 to 150 Ω
c. 75 to 400 Ω
d. 75 to 600 Ω

a. 150 to 600 Ω

The characteristic impedance of coaxial cable varies from
a. 150 to 600 Ω
b. 40 to 150 Ω
c. 75 to 400 Ω
d. 75 to 600 Ω

b. 40 to 150 Ω

Often inserted in telephone lines at spacing as close as 1 mile (1.6 km), to counteract the capacitance of the line and thus make the line impedance more closely equivalent to a pure resistance
a. Amplifiers
b. Transformer
c. Equalizer
d. Loading coils

d. Loading coils

When the receiving end of the wire is an open circuit, it is a point of
a. Maximum current and zero voltage
b. Maximum voltage and zero current
c. Zero current and zero voltage
d. Maximum voltage and maximum current

b. Maximum voltage and zero current

If a wire is terminated on a short circuit, the end of the wire is a point of
a. Maximum current and zero voltage
b. Maximum voltage and zero current
c. Zero current and zero voltage
d. Maximum voltage and maximum current

a. Maximum current and zero voltage

The principal method of reducing noise and crosstalk to low value on open-wire lines
a. Filter method
b. Scrambling
c. Feedback
d. Transposing

d. Transposing

Used for VHF antennas
a. RG-214/U
b. RG-59/U
c. RG-11/U
d. RG-58/U

d. RG-58/U

Which transmission line has the highest attenuation?
a. RG-214/U
b. RG-59/U
c. RG-11/U
d. Twin lead

b. RG-59/U

Which transmission line has the lowest attenuation?
a. RG-214/U
b. RG-59/U
c. RG-11/U
d. Twin lead

d. Twin lead

A widely used transmission line, in which two stranded wires are separated by a flat continuous plastic insulator
a. RG-214/U
b. RG-59/U
c. RG-11/U
d. Twin lead

d. Twin lead

Used for TV antennas; cable TV; and HF antennas
a. RG-214/U
b. RG-59/U
c. RG-11/U
d. RG-58/U

b. RG-59/U

An open-wire line has an attenuation of 2.4 dB per 100 ft. The attenuation for 275 ft is
a. 2.4 dB
b. 3.3 dB
c. 4.8 dB
d. 6.6 dB

d. 6.6 dB

The ratio of velocity of propagation in the transmission line and the velocity of propagation in free space
a. Wavelength constant
b. Propagation constant
c. Velocity factor
d. Velocity of light

c. Velocity factor

This transmission line is used in microwave circuits. It consists of a narrow, flat conductor sandwiched between dielectric boards whose outside surfaces are coated with conductor
a. Stripline
b. Microstrip
c. Waveguide
d. Coax

a. Stripline

Is a narrow, flat conductor on a single dielectric board whose opposite face is metallized, much like an ordinary printed-circuit board. It is also used in microwave circuits
a. Stripline
b. Microstrip
c. Waveguide
d. Coax

b. Microstrip

Can be placed at either end of a transmission line to convert between 72-Ω unbalanced line to a 300-Ω balance line
a. Stub
b. Resonant circuit
c. Balun
d. Coupler

c. Balun

Power loss due to increased effective resistance of a conductor at microwave frequencies due to skin effect
a. Conduction loss
b. Radiation loss
c. Dielectric loss
d. Corona

a. Conduction loss

When does a transmission line terminated in a short look like a short to the source?
a. At quarter-wavelength
b. At half-wavelength
c. At less than λ/5
d. At less than λ/4

b. At half-wavelength

How many cycles of a 1 MHz wave can a 6-mile transmission line accommodate?
a. 60 cycles
b. 6 cycles
c. 16.67 cycles
d. 32.26 cycles

c. 16.67 cycles

A transmission line has a capacitance of 25 pF/ft and an inductance of 0.15 μH/ft. Determine the characteristic impedance of the line.
a. 77.5 Ω
b. 50 Ω
c. 75 Ω
d. 100 Ω

a. 77.5 Ω

For a transmission line giving a maximum RMS voltage reading of 50 V at one point and a minimum RMS voltage reading of 25 V at another point. What is the VSWR of the line?
a. 2
b. 4
c. 1
d. 5

a. 2

Two 2-mm-diameter wires held 6 cm apart center-to-center has a characteristic impedance of_______.
a. 500 Ω
b. 250 Ω
c. 491 Ω
d. 75 Ω

c. 491 Ω

Does minimum or maximum VSWR indicate best matching of antenna to transmission line?
a. Minimum
b. Maximum
c. Either a or b
d. Neither a or b

a. Minimum

If two towers of a 1100-kHz array are separated by 120°, what is the tower separation in feet?
a. 321
b. 48
c. 298
d. 412

a. 321

What is the reflection coefficient of an open-circuited transmission line?
a. 1
b. -1
c. 0
d. Infinity

a. 1

The reflection coefficient on a transmission line is 1/3, what is the SWR?
a. 0
b. 3
c. 2
d. 4

c. 2

Indicate the false statement. The SWR on a transmission line is infinity: the line is terminated in a/an
a. Short circuit
b. Open circuit
c. Pure reactance
d. Complex impedance

d. Complex impedance

Coaxial lines are used on those systems operating_______
a. Below 2 GHz
b. At 300 MHz
c. Above 10 kHz
d. Above 10 GHz

a. Below 2 GHz

What is the SWR along a transmission line having a characteristic impedance of 75 Ω and a load impedance of 300 Ω?
a. 0.25
b. 4
c. 2
d. 0.5

b. 4

Who developed the Smith Chart?
a. Philip H. Smith
b. James N. Smith
c. Philip S. Chart
d. Gunn Chart

a. Philip H. Smith

An electronic equipment used to measure standing wave ratio.
a. Reflectometer
b. Wavemeter
c. Altimeter
d. Multimeter

a. Reflectometer

What is the phase shift corresponding to λ / 4 in standing wave pattern?
a. 0°
b. 40°
c. 90°
d. 180°

c. 90°

For a parallel resonant circuit, a λ / 4 stub must be_____ at the ends.
a. Open
b. Shorted
c. Loaded
d. Complex

b. Shorted