Deck 12: Transmission Lines

Question 1

When current travels in a wire,what is created?
A.High frequencies
B.Electromagnetic field
C.Crosstalk
D.Increase in signal-transmission performance

Answer 1

Electromagnetic field

Question 2

What type of cable must not be stepped on,crimped,or bent in too small a radius?
A.Coaxial
B.Flexible
C.Electrical
D.Solid dielectric

Answer 2

Coaxial

Question 3

What are circuits called that convert between balanced and unbalanced operation?
A.Power-sum
B.Coaxial
C.Baluns
D.Dielectric

Answer 3

aluns

Question 4

What does power-sum testing measure?
A.Total crosstalk of all cable pairs
B.Diameter of copper, cable handling, and dielectric differences
C.Signal reflection results from impedance changes
D.Any noise or unwanted signal picked up by the balanced line

Question 5

A _________ is a transmission line that is terminated with an impedance that is not equal to its characteristic impedance.
A.nonresonant line
B.line wavelength
C.terminated line
D.resonant line

Question 6

What is one of the simplest and yet most useful measuring instruments at very high frequencies?
A.Time-domain reflectometry
B.Slotted line
C.Double-stub tuner
D.Balun

Question 7

_____________is a measure of the difference in time between the fastest and the slowest wire pair in a UTP cable.
A.Attenuation
B.Reflection
C.Return loss
D.Delay skew

Question 8

Three major losses occur in transmission lines: copper,radiation or induction,and ______________.
A.electric
B.dielectric
C.power
D.voltage

Question 9

The _________ characteristics of the two-wire transmission line depend primarily on the construction of the line.
A.electrical
B.magnetic
C.radiation
D.conductive

Question 10

The problem of radiation loss is of consequence for only what type of transmission lines?
A.Unshielded twisted-pair
B.Twisted pair
C.Parallel-wire
D.Shielded pair

Question 11

What is one the most useful properties of the Smith chart?
A.Its ability to solve impedance-matching problems.
B.It is an easy measure indication of the severity of mismatch.
C.It exhibits properties of inductance and capacitance.
D.It can determine the effects on impedance of changes to component values.

Question 12

What is the principal advantage of the shielded pair?
A.Inexpensive to construct
B.Measures difference in time between fastest and slowest wire pair
C.Transmit-signal levels strong
D.Conductors balanced to ground

Question 13

What substance is commonly used as the dielectric in transmission lines?
A.Teflon
B.Pyrex
C.Rubber
D.Copper

Question 14

____________ are hollow tubes used to conduct electromagnetic energy at microwave frequencies.
A.Antennas
B.Transmission lines
C.Cables
D.Waveguides

Question 15

Which of the following would measure of the level of crosstalk,or signal coupling,within a cable?
A.Delay skew
B.Near-end crosstalk (NEXT)
C.Standing wave ratio (SWR)
D.Voltage standing wave ratio (VSWR)

Question 16

What speed does a wave that is radiated through "free space" travel?
A.Speed of light
B.Speed of sound
C.Actual velocity
D.Velocity of propagation

Question 17

A very common problem with transmission line communications involves what type of failure between communications terminals?
A.Capacitor
B.Antenna
C.Cable
D.Voltage

Question 18

Which of the following is a disadvantage of not having a perfectly matched (flat line)system?
A.The existence of reflections increases the power surge.
B."Ghost" signals can be destroyed.
C.The full generator power does not reach the load.
D.Noise problems are increased by matches.

Question 19

What is the ratio of reflected voltage to incident voltages called?
A.Voltage standing-wave ratio
B.Reflection coefficient
C.Return loss
D.Standing wave

Question 20

A ___________ is created as the result of the instantaneous vector addition of the incident-wave amplitude with that of the reflected wave created as the result of impedance mismatch between the transmission line and the load.
A.flat line
B.wavelength
C.traveling wave
D.standing wave

Question 21

The shielded pair consists of parallel conductors separated from each other,and surrounded by a solid dielectric. Which of the following materials acts as the shield?
A.Copper braid tubing
B.Polystyrene
C.Insulating spacers
D.Inert gases

Question 22

The resistance of any conductor is never zero _________.
A.ohms
B.voltage
C.current
D.impedance

Question 23

A ______________ terminated in an open has a reflected voltage wave that is always of the same polarity and amplitude as the incident voltage wave.
A.transmission line
B.magnetic field
C.wavelength
D.circuit

Question 24

What substance allows the construction of a flexible cable whose dielectric losses,though higher than air,are still much lower than the losses that occur with other types of low-cost dielectrics?
A.Rubber
B.Polyethylene
C.Teflon
D.Pyrex