Deck 12: Transmission Lines

Question 1

A transmission line having a delay time of 45 microseconds and terminated with an open is applied with a 4 VDC incident voltage. At the load end of the line:

A) the voltage changes from 0V to -4V at t = 45 microseconds.
B) the voltage changes from 0V to 8V at t = 45 microseconds.
C) the voltage changes from 0V to 4V at t = 40 microseconds.
D) the voltage changes from 0V to 4V at t = 45 microseconds.
E) the voltage changes from 0V to 8V to t = 90 microseconds.

Answer 1

B

Question 2

If the length of a section of RG-59 coaxial cable is doubled, its velocity factor will:

A) decrease
B) increase
C) remain the same.

Answer 2

C

Question 3

A transmission line that is terminated with a resistive load that is equal to the characteristic impedance of the line is called:

A) reactive
B) lossy
C) resonant
D) nonresonant

Answer 3

D

Question 4

A non-lossy transmission line terminated with an open circuit will have:

A) an opposite-phase reflected current that is smaller in magnitude than the incident current.
B) an in-phase reflected current that is smaller in magnitude than the incident current.
C) an opposite-phase reflected current that is equal in magnitude to the incident current.
D) an in-phase reflected current that is equal in magnitude to the incident current.

Question 5

A transmission line that is terminated with an impedance that is not equal to its characteristic impedance is called:

A) nonresonant
B) reactive
C) resonant
D) lossy

Question 6

What makes conductors behave differently at high frequencies than they do at low frequencies?

A) At high frequencies, there are many sources of line loss.
B) At high frequencies, there are inductive, capacitive, and resistive effects to transmission lines.
C) At high frequencies, energy sent down a wire may be reflected back.
D) all of the above.

Question 7

Which of the following is not an application of a transmission line?

A) filters
B) balanced lines
C) discrete circuit simulation
D) impedance match

Question 8

A commonly used coaxial cable, RG-58, has a characteristic impedance of 50 ohms. If the spacing between the conductors is doubled, its characteristic impedance will:

A) remain the same.
B) decrease.
C) increase.

Question 9

Which will reduce the radiation loss of transmission line?

A) use better shielding
B) terminate the line with a resistive load equal to the transmission line's characteristic impedance
C) use coaxial transmission line
D) all of the above

Question 10

Which of the following can be determined using a slotted line method?

A) generator frequency
B) unknown load impedance
C) VSWR
D) all of the above

Question 11

A non-lossy transmission line terminated with an open circuit will have:

A) an opposite-phase reflected voltage that is smaller in magnitude than the incident voltage.
B) an opposite-phase reflected voltage that is equal in magnitude to the incident voltage.
C) an in-phase reflected voltage that is equal in magnitude to the incident voltage.
D) an in-phase reflected voltage that is smaller in magnitude than the incident voltage.

Question 12

A transmission line terminated with an open has a VSWR of:

A) +1.
B) 0.
C) infinity.
D) -1.

Question 13

In a conductor at high frequencies, most of the current flow is at the outer surface of the conductor. This phenomena is known as:

A) the skin effect.
B) radiation loss.
C) resistive attenuation.
D) induction loss.
E) surface loss.

Question 14

Determine the amount of delay in a 200 ft. section of RG-8A/U coaxial cable if its inductance is 73.75 nH per ft. and its capacitance is 29.5 pf per ft.

A) 217.5 ns
B) 49.9 ns
C) 295 ns
D) 9.983 us

Question 15

A non-lossy transmission line terminated with a short circuit will have:

A) an in-phase reflected current that is smaller in magnitude than the incident current.
B) an in-phase reflected current that is equal in magnitude to the incident current.
C) an opposite-phase reflected current that is equal in magnitude to the incident current.
D) an opposite-phase reflected current that is smaller in magnitude than the incident current.

Question 16

A commonly used coaxial cable, RG-58, has a characteristic impedance of 50 ohms. If its length is doubled, its characteristic impedance will:

A) remain the same.
B) decrease.
C) increase.

Question 17

What is an advantage of open-wire line over coaxial cable?

A) low inductive loss
B) simple construction
C) low noise pickup
D) low radiation loss

Question 18

Which of the following is a definition of characteristic impedance?

A) coaxial line impedance
B) impedance of infinite line
C) impedance at front end
D) impedance at any point

Question 19

When moving from the source to load, current and voltage traveling waves move:

A) 90 phase shift
B) 60 phase shift
C) 30 phase shift
D) no phase shift

Question 20

One use of a quarter-wavelength transformer is:

A) match line resistance to load resistance.
B) shift voltage.
C) step down current.
D) all of the above.

Question 21

The center of the Smith chart represents:

A) a short circuit load impedance.
B) a matched load impedance.
C) a 1 ohm load impedance.
D) an open circuit load impedance.

Question 22

Moving a full revolution around an SWR circle on the Smith chart represents:

A) moving a half-wavelength down the transmission line.
B) moving a quarter-wavelength down the transmission line.
C) moving a full wavelength down the transmission line.
D) moving two wavelengths down the transmission line.

Question 23

The disadvantage of not having a perfectly matched transmission line in a communication system is:

A) the cable dielectric may break down.
B) the existence of reflections increases the power loss.
C) noise problems are increased.
D) the fully generated power does not reach the load.
E) none of the above

Question 24

A pulse-technique used in determining the location of a fault in a transmission line is called:

A) stub tuning.
B) time-domain reflectometry.
C) SWR measurements.
D) slotted-line measurements.

Question 25

Wiring of the RJ-45 connector CAT6 cable is defined by the telecommunications industry standard:

A) ACR
B) 802.3
C) TIA 568B
D) 802.11
E) None of the above

Question 26

The input impedance of a quarter-wavelength section of 50 ohm transmission line that is terminated with an open is:

A) 0 ohms (a short).
B) 50 ohms.
C) infinite (open).
D) 100 ohms.

Question 27

A transmission line terminated with an open has a reflection coefficient at the load of:

A) 0.
B) -1.
C) +1.
D) infinity.

Question 28

A transmission line terminated with a load resistance that is equal to the transmission line's characteristic impedance has a reflection coefficient at the load of:

A) -1.
B) +1.
C) infinity.
D) 0.

Question 29

A transmission line terminated with a short has a reflection coefficient at the load of:

A) -1.
B) +1
C) 0.
D) infinity.

Question 30

CAT 5e cable can handle a 100MHz bandwidth up to a length of:

A) 22 meters
B) 110 meters
C) 100 meters
D) 90 meters
E) 330 meters

Question 31

A quarter-wavelength transmission line is terminated with a 300 ohm load. Its input impedance is 75 ohms. Its characteristic impedance is:

A) 75 ohms.
B) 150 ohms.
C) 50 ohms.
D) 300 ohms.
E) 187.5 ohms.

Question 32

A transmission line terminated with a short has a VSWR of:

A) -1.
B) +1.
C) 0.
D) infinity.

Question 33

33. The perimeter of the Smith chart graph represents:

A) the SWR of a transmission line terminated with an open circuit.
B) an infinite SWR circle.
C) the SWR of a transmission line terminated with a short circuit.
D) all of the above

Question 34

At resonance, a series RLC circuit will be:

A) capacitive only
B) inductive only
C) resistive only
D) reactive
E) none of the above

Question 35

A transmission line terminated with a load resistance that is equal to the transmission line's characteristic impedance has a VSWR of:

A) -1.
B) infinity.
C) +1
D) 0.

Question 36

A 50 ohm transmission line that has a load impedance of 300 ohms has a reflection coefficient of:

A) 6.
B) 0.666.
C) 0.166.
D) -0.714.
E) 0.714.

Question 37

The CAT1 specification for twisted pair:

A) never existed
B) same as TIA 568B
C) CAT 4
D) same as CAT3
E) none of the above

Question 38

Near-end crosstalk is best defined as

A) a desired performance objective
B) a measure of the signal coupling outside the cable
C) a measure of the level in side the cable
D) a measure of the level of crosstalk within a cable
E) none of the above

Question 39

The input impedance of a half-wavelength section of 50 ohm transmission line that is terminated with an open is:

A) 100 ohms.
B) 50 ohms.
C) 0 ohms (a short).
D) infinite (open).

Question 40

ACR is a combined measurement of

A) CAT3 and CAT5
B) T568A and T568B
C) crosstalk and PSNEXT
D) attenuation and crosstalk
E) none of the above