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Transmission Lines

1. SWR stands for:

A. Shorted Wave Radiation

B. Sine Wave Response

C. Shorted Wire Region

D. None of the choices

2. TDR stands for:

A. Total Distance of Reflection

B. Time-Domain Reflectometer

C. Time-Domain Response

D. Transmission Delay Ratio

3. An example of an unbalanced line is:

A. A coaxial cable

B. 300-ohm twin-lead TV cable

C. An open-wire-line cable

D. All of the choices

4. When analyzing a transmission line, its inductance and capacitance are considered to be:

A. lumped

B. distributed

C. Equal reactance

D. Ideal elements

5. As frequency increases, the resistance of a wire:

A. increases

B. decreases

C. Stays the same

D. Changes periodically

6. The effect of frequency on the resistance of a wire is called:

A. I2R loss

B. the Ohmic effect

C. The skin effect

D. There is no such effect

7. As frequency increases, the loss in a cable's dielectric:

A. increases

B. decreases

C. Stays the same

D. There is no loss in a dielectric

8. The characteristic impedance of a cable depends on:

A. The resistance per foot of the wire used

B. The resistance per foot and the inductance per foot

C. The resistance per foot and the capacitance per foot

D. The inductance per foot and the capacitance per foot

9. For best matching, the load on a cable should be:

A. Lower than Z0

B. Higher than Z0

C. Equal to Z0

D. 50 ohms

10. The characteristic impedance of a cable:

A. Increases with length

B. Increases with frequency

C. Increases with voltage

D. None of the choices

11. The velocity factor of a cable depends mostly on:

A. The wire resistance

B. The dielectric constant

C. The inductance per foot

D. All of the choices

12. A positive voltage pulse sent down a transmission line terminated in a short circuit:

A. Would reflect as a positive pulse

B. Would reflect as a negative pulse

C. Would reflect as a positive pulse followed by a negative pulse

D. Would not reflect at all

13. A positive voltage pulse sent down a transmission line terminated with its characteristic impedance:

A. Would reflect as a positive pulse

B. Would reflect as a negative pulse

C. Would reflect as a positive pulse followed by a negative pulse

D. Would not reflect at all

14. A positive voltage-pulse sent down a transmission line terminated in an open-circuit:

A. Would reflect as a positive pulse

B. Would reflect as a negative pulse

C. Would reflect as a positive pulse followed by a negative pulse

D. Would not reflect at all

15. The optimum value for SWR is:

A. zero

B. one

C. As large as possible

D. There is no optimum value

16. A non-optimum value for SWR will cause:

A. Standing waves

B. Loss of power to load

C. Higher voltage peaks on cable

D. All of the choices

17. VSWR stands for:

A. variable SWR

B. vacuum SWR

C. voltage SWR

D. None of the above

18. The impedance "looking into" a matched line:

A. Is infinite

B. Is zero

C. Is the characteristic impedance

D. 50 ohms

19. A Smith Chart is used to calculate:

A. Transmission line impedances

B. Propagation velocity

C. Optimum length of a transmission line

D. Transmission line losses

20. Compared to a 300-ohm line, the loss of a 50-ohm cable carrying the same power:

A. Would be less

B. Would be more

C. Would be the same

D. Cannot be compared

21. A balanced load can be connected to an unbalanced cable:

A. directly

B. By using a filter

C. By using a "balun"

D. Cannot be connected

22. On a Smith Chart, you "normalize" the impedance by:

A. Assuming it to be zero

B. Dividing it by 2π

C. Multiplying it by 2π

D. Dividing it by Zo

23. The radius of the circle you draw on a Smith Chart represents:

A. The voltage

B. The current

C. The impedance

D. None of the choices

24. The center of the Smith Chart always represents:

A. zero

B. one

C. The characteristic impedance

D. None of the choices

25. A TDR is commonly used to:

A. Measure the characteristic impedance of a cable

B. Find the position of a defect in a cable

C. Replace a slotted-line

D. All of the choices

26. Which of the following is a definition of characteristic impedance?

A. Coaxial line impedance

B. Impedance at any point

C. Impedance of infinite line

D. Impedance at front end

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

A. 30° phase shift

B. 60° phase shift

C. 90° phase shift

D. No phase shift

28. One use of a quarter-wavelength transformer is:

A. Step down current

B. Match line resistance to load resistance

C. Shift voltage

D. All of the choices

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

A. Impedance match

B. filters

C. Balanced lines

D. Discrete circuit simulation

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

A. VSWR

B. Generator frequency

C. Unknown load impedance

D. All of the choices

31. 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, energy sent down a wire may be reflected back.

C. At high frequencies, there are inductive, capacitive, and resistive effects to transmission lines.

D. All of the choices

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

A. Low radiation loss

B. Low noise pickup

C. Simple construction

D. Low inductive loss

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

A. increase

B. decrease

C. Remain the same

D. Lacks data

34. 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. increase

B. decrease

C. Remain the same

D. Lacks data

35. 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. Radiation loss

B. The skin effect

C. Induction loss

D. Resistive attenuation

36. Which will reduce the radiation loss of transmission line?

A. Use coaxial transmission line

B. Use better shielding

C. Terminate the line with a resistive load equal to the transmission line's characteristic impedance

D. All of the choices

37. 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. 295 ns

C. 49.9 ns

D. 9.983 us

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

A. increase

B. decrease

C. Remain the same

D. Lacks data

39. 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. resonant

C. lossy

D. nonresonant

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

A. reactive

B. resonant

C. lossy

D. nonresonant

41. 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 8V at t = 45 microseconds

B. The voltage changes from 0V to 4V at t = 45 microseconds

C. The voltage changes from 0V to -4V at t = 45 microseconds

D. The voltage changes from 0V to 4V at t = 45 microseconds

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

A. An in-phase reflected voltage that is equal in magnitude to 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 smaller in magnitude than the incident voltage

D. An opposite-phase reflected voltage that is smaller in magnitude than the incident voltage

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

A. An in-phase reflected current that is equal in magnitude to the incident current

B. An opposite-phase reflected current that is equal in magnitude to the incident current

C. An in-phase reflected current that is smaller in magnitude than the incident current

D. An opposite-phase reflected current that is smaller in magnitude than the incident current

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

A. An in-phase reflected current that is equal in magnitude to the incident current

B. An opposite-phase reflected current that is equal in magnitude to the incident current

C. An in-phase reflected current that is smaller in magnitude than the incident current

D. An opposite-phase reflected current that is smaller in magnitude than the incident current

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

A. -1

B. 0

C. +1

D. infinity

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

A. -1

B. 0

C. +l

D. infinity

47. 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. 0

C. +l

D. infinity

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

A. -1

B. 0

C. +l

D. infinity

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

A. -1

B. 0

C. +l

D. infinity

50. 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. 0

C. +l

D. infinity

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

A. 6

B. 0.166

C. -0.714

D. 0.714

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

A. The fully generated power does not reach the load

B. The cable dielectric may break down

C. The existence of reflections increases the power loss

D. All of the choices

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

A. 50 ohms

B. 0 ohms (a short)

C. infinite (open)

D. 100 ohms

54. The input impedance of a half-wavelength section of 50 ohm transmission line that is terminated with a short is

A. 50 ohms

B. 0 ohms (a short)

C. infinite (open).

D. 100 ohms

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

A. 50 ohms

B. 0 ohms (a short)

C. infinite (open)

D. 100 ohms

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

A. Moving a quarter-wavelength down the transmission line

B. Moving a half-wavelength down the transmission line

C. Moving a full wavelength down the transmission line

D. Moving two wavelengths down the transmission line

57. The center of the Smith chart represents:

A. An open circuit load impedance

B. A short circuit load impedance

C. A matched load impedance

D. a 1 ohm load impedance

58. The perimeter of the Smith chart graph represents:

A. the SWR of a transmission line terminated with an open circuit

B. the SWR of a transmission line terminated with a short circuit

C. An infinite SWR circle

D. All of the choices

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

A. 50 ohms

B. 75 ohms

C. 150 ohms

D. 187.5 ohms

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

A. slotted-line measurements

B. SWR measurements

C. time-domain reflectometry

D. Stub tuning

61. Near-end crosstalk is best defined as

A. A measure of the level of crosstalk within a cable

B. A measure of the signal coupling outside the cable

C. A measure of the level inside the cable

D. A desired performance objective

62. CAT5e cable can handle a l00 MHz bandwidth up to a length of:

A. 22 meters

B. 110 meters

C. 330 meters

D. 100 meters

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

A. 802.3

B. 802.11

C. ACR

D. TIA 568B

64. ACR is a combined measurement of

A. T568A and T568B

B. Attenuation and crosstalk

C. Crosstalk and PSNEXT

D. CAT3 and CAT5

65. The CAT1 specification for twisted pair:

A. Same as CAT3

B. Same as TIA 568B

C. Never existed

D. CAT4

66. An impedance value of Z=l+j0 indicates it is:

A. capacitive

B. inductive

C. 50 Ω

D. Purely resistive

67. The characteristic impedance of a network analyzer is set to 50Ω. A ZT =0.5+j0.5 translates to:

A. 25+j0

B. 50+j25

C. 25+j25

D. 25+j50

68. At resonance, a series RLC circuit will be:

A. Resistive only

B. Capacitive only

C. Inductive only

D. reactive

69. If the SWR on a transmission line is infinity, therefore the line is terminated in______(false statement).

A. A short circuit

B. A complex impedance

C. An infinite load impedance

D. A pure reactance

70. A (25-j50)Ω is connected to a coaxial transmission line of Zo = 25 Ω, at 7 GHz. The best method of matching is:

A. A iris placed closest to the load

B. An inductance at the load

C. A capacitance at some specific distance

D. A short-circuited stub at some specific distance from the load

71. Which of the following is true about the velocity factor of a transmission line?

A. Depends on the dielectric constant of the material used

B. Increases the velocity along the transmission line

C. Is inversely proportional with the speed of light

D. Is higher for a solid dielectric than for air

72. Impedance inversion can happen in:

A. A short-circuited stub

B. a 0.707 wavelength of the line

C. A quarter-wave line

D. A half-wave line

73. Why are short-circuited stubs preferred than open- circuited stubs?

A. short-circuited stubs are more difficult to make an connect

B. short-circuited stubs are made of a transmission line with a different

C. open-circuited stubs are liable to radiate

D. open-circuited incapable of giving a full range of reactance

74. In load matching for a transmission-line over a range of frequencies, the best device is:

A. balun

B. Q section

C. Double stub

D. Single stub of adjustable position

75. Which is the main disadvantage of the two-hole directional coupler?

A. Difficulty in creating the holes

B. Poor directivity

C. high SWR

D. Narrow bandwidth

76. Used for coaxial line to a parallel-wire line coupling:

A. Slotted line

B. balun

C. isolator

D. quarter-wave transformer

Use the statement below to answer the next 4 questions. A commonly used coaxial cable, RG-8A/U, has a capacitance of 29.5 pF/ft and inductance of 73.75 nH/ft.

Determine its characteristic impedance for a 1 mi.

A. 100 Ω

B. 75 Ω

C. 50 Ω

D. 53 Ω

78. Determine its characteristic impedance for a 1ft.

A. 100 Ω

B. 75 Ω

C. 50 Ω

D. 53 Ω

79. Determine the amount of delay for a 1 ft section.

A. 1.475 ns

B. 4.751 ns

C. 5.712 ns

D. 2.231 ns

80. Determine the velocity of propagation introduced by 1 ft section.

A. 2.07 x 10^8 m/s

B. 3 x 10^8 m/s

C. 4.33 x 10^8 m/s

D. 2.673 x 10^8 m/s

81. Determine the characteristic impedance of a parallel wire line with D/d= 2 with air dielectric.

A. 166 Ω

B. 51.2 Ω

C. 50 Ω

D. 74 Ω

82. Determine the characteristic impedance of a parallel wire line with D/d= 2.35 with air dielectric.

A. 166 Ω

B. 51.2 Ω

C. 50 Ω

D. 74 Ω

83. Determine the characteristic impedance of RG-8A/U coaxial cable with D = 0.285 in. And d = 0.08 in. It uses a polyethylene dielectric.

A. 166 Ω

B. 51.2 Ω

C. 50 Ω

D. 74 Ω

84. Determine the wavelength of a 100 MHz signal in free space.

A. 1 m

B. 2 m

C. 3 m

D. 4 m

85. Determine the wavelength of a 100 MHz while traveling through an RG-8A/U coaxial cable.

A. 1 m

B. 2 m

C. 3 m

D. 4 m

Use the statement below to answer the next 4 questions. A citizen's band transmitter operating at 27 MHz with 4W output is connected via 10 m of RG-8A/U cable to an antenna that has an input resistance of 300 Ω.

Find the reflection coefficient.

A. 0.61

B. 0.5

C. 0.36

D. 0.71

87. Find the electrical length of the cable in wavelengths.

A. 2 λ

B. 3 λ

C. 1.3 λ

D. 2.1 λ

88. Determine the VSWR.

A. 4

B. 2

C. 4

D. 6

89. Find the amount of the transmitter's 4 W output absorbed by the antenna.

A. 2.23 W

B. 1.55 W

C. 4W

D. 1.96 W

Use the statement below to answer the next 3 questions. The forward power in a transmission line is 150 W, and the reverse power is 20 W.

Solve for the reflection coefficient.

A. 0.675

B. 0.365

C. 0.243

D. 0.764

91. Calculate the SWR on the line.

A. 2.15

B. 5.12

C. 1.12

D. 2.66

92. Determine the power absorbed.

A. 150 W

B. 20 W

C. 130 W

D. 76 W

93. 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. 336 m

B. 112 m

C. 787 m

D. 168 m

94. To match the 50 Ω line at a frequency of 100 MHz to a load with ZL = 50 + j75 Ω

A. Use a capacitor C = 21.2 pF

B. Use an inductor L = 21.2 nH

C. Use a capacitor C = 12.2 pF

D. Use an inductor L = 12.2 nH

Use the statement below to answer the next 2 questions. A transmitter is required to deliver 100W to an antenna through 45 m of coaxial cable with a loss of 4 dB/100 m.

How much is the loss in dB?

A. 2.1 dB

B. 7.7 dB

C. 1.8 dB

D. 3 dB

96. What must be the output power of the transmitter, assuming the line is matched?

A. 511 W

B. 121 W

C. 151 W

D. 78 W

97. A series tuned circuit operating at a frequency of 1 GHz is to be constructed from a shorted section of air-dielectric coaxial cable. What length should be used?

A. 0.285 m

B. 0.142 m

C. 0.455 m

D. 2 m

Use the statement below to answer the next 2 questions. A transmitter supplies 50 W to a load through a line with an SWR of 2:1.

Find the power absorbed by the load.

A. 44.44 W

B. 5.55 W

C. 33.33 W

D. 31.5 W

99. Find the reflection coefficient.

A. 0.77

B. 0.33

C. o.23

D. 0.89

100. Find the propagation velocity for a cable with a Teflon dielectric (εr=2).

A. 207 x 10^6 m/s

B. 278 x 10^6 m/s

C. 3 x 10^8 m/s

D. 2.88 x 10^8 m/s

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