TRANSMISSION LINES

Transmission Lines

1. When the transmission line is matched to the load, it

a. Transfers maximum current to the loadb. Transfers maximum voltage to the loadc. Transfers maximum power to the loadd. Reduces the load current

2. To couple a coaxial line to a parallel wire line, it is best to use a _____

a. Slotted lineb. Directional couplerc. Balund. Quarter wavelength transformer

3. To be properly matched, the ratio of maximum to minimum voltage along a transmission line should be equal to

a. 50

b. 10

c. 2

d. 1

4. For transmission line load matching over a range of frequencies, it is best to use a

a. Balunb. Broadband directional coupler

c. Double stubd. Single adjustable stub

5. The property of a material that determines how much electrostatic energy can be stored per unit volume when voltage is applied.

a. Permeabilityb. Magnetic effectc. Capacitanced. Permittivity6. When mismatch is great, this power actually cause damage to the transmitter or the line itself.

a. The incident powerb. The reflected powerc. The power dissipationd. The carrier power7. The measure of the superiority of a material over vacuum as a path for magnetic lines of force is

a. Permitivityb. Permeability

c. Conductivityd. Resistivity

8. A coax line has an attenuation of 2.4 dB per 100 ft. The attenuation for 2.75 ft. is ____ dB.

a. 2.4

b. 4.8

c. 3.3

d. 6.6

9. The characteristic impedance of a transmission line is determined by

a. Its lengthb. Its height above ground

c. Its physical constructiond. The operating frequency

10. Considering a coaxial transmission line, maximum voltage on the line divided by the minimum voltage equals the

a. Characteristic Impedance

b. ISWR

c. VSWR

d. Inductive Reactance

11. Transmission lines are either balanced or unbalanced with respect to

a. Negative terminal

b. Input

c. Ground

d. Positive terminal

12. The radiation resistance of a quarter wave antenna is

a. 49 ohms

b. 288 ohms

c. 72 ohms

d. 144 ohms

13. The VSWR for a line terminated in its Zo is

a. 0

b. 1

c. 1.5

d. Infinity14. A 75-j50 ohm load is connected to a coaxial transmission line of Z0 = 75 ohms at 10GHz. The best method of matching consists in connecting

a. A short-circuited stub at the loadb. A capacitance at some specific distance from the loadc. An inductance at the loadd. A short-circuited stub at some specific distance from the load

15. A resultant wave due to the combination of incident and reflected wave.

a. Electromagnetic waveb. Sine wavec. Standing waved. Current16. If the load impedance matches the characteristic impedance of the line, there are __________ standing waves.

a. Moreb. Lessc. Nod. Ten (10)

17. Reflections on a transmission line can occur whena. Impedance of the source and load are matchedb. Impedance of the source and the load are mismatchedc. Resonance conditions are obtainedd. Power transfer between source and load is maximum18. A measure of the mismatch between line and load impedance is called asa. Reflection coefficientb. Standing wave ratioc. Lossd. Standing waves

19. At matched condition, SWR is equal toa. Zerob. Onec. 100

d. Infinite20. A characteristic of an infinite transmission line is thata. The impedance in equals impedance outb. It carries waves at the velocity of light

c. It can be connected to mismatched loadsd. The impedance varies with the length of the line21. The outer conductor of a coaxial transmission line is usually grounded at the:

a. Input and outputb. Output onlyc. Input only

d. Point of infinite resistance

22. If the input impedance of an antenna is 300 ohms and it is fed with a 600 ohm balanced transmission line, the SWR on the line is

a. 4

b. 3

c. 2

d. 0.5

23. The ratio of the reflected voltage to the incident voltage on the transmission line is termed as

a. Reflection coefficientb. Standing wave ratioc. Lossd. Standing waves

24. Termination meansa. Load connected to the output end of a transmission lineb. Result of disconnecting a line from a transmitter

c. Looking back impedance of a line with no loadd. Result of cutting both ends of a conductor25. Permeability is the measure of superiority of a material over vacuum as a path of magnetic lines of force. The permeability of free space is equal to ______ henry/metera. 1.257 x 10exp-6

b. 1.527 x 10exp 6

c. 7.251 x 10exp-6

d. 5.217 x 10exp-6

26. The characteristic impedance of a transmission line does not depend upon itsa. Lengthb. Conductor diameterc. Conductor spacing

d. Thickness of armor27. It is required to match a 73-ohm antenna to a 600 ohm polyethylene coaxial feeder line, with a velocity factor of 0.66 by means of a quarter wave matching transformer. At a frequency of 150 MHz, the impedance of the matching section is ________ ohms.a. 209.28

b. 310.5

c. 150.28

d. 450.82

28. The characteristic impedance of a transmission line is the impedance measured at the _____ when its length is infinite.a. Shorted end of the lineb. Midsectionc. Input

d. Output

29. It is required to match a 200 ohm load to a 300 ohm transmission line to reduce the SWR and attain resonance. A quarter wave transformer used, directly connected to the load has a Zo of ______ ohms.a. 245

b. 425

c. 524

d. 254

30. The mismatch between antenna and transmission line impedances cannot be corrected bya. Using an LC network

b. Adjusting antenna length

c. Using a balun

d. Adjusting the length of the transmission line

31. The most desirable value of SWR on a transmission line isa. 0

b. 1

c. 2

d. Infinity32. At very high frequencies, transmission lines are used as ________

a. Tuned circuitsb. Antennas

c. Insulators

d. Resistors33. The minimum voltage along a transmission line is 260 volts, while the maximum is 390 volts. The SWR isa. 0.67

b. 1.0

c. 1.2

d. 1.5

34. What characteristic impedance is needed to match a 50-ohm line to a 300 ohm-load?a. 221 ohms

b. 122 ohms

c. 212 ohms

d. 112 ohms

35. A (75 j50) -( load is connected to a coaxial transmission line of Zo = 75 (, at 10 GHz. The best method of matching consists in connectinga. A short-circuited stub at the loadb. An inductance at the loadc. A capacitance at some specific distance from the load

d. A short-circuited stub at some specific distance from the load36. What is the characteristic impedance of a single wire with diameter d = 0.25 mm placed at the center between grounded parallel planes separated by 1 mm apart. The wire is held by a material with a velocity factor of 0.75.a. 85 ohms

b. 63 ohms

c. 50 ohms

d. 75 ohms

37. Referred to the dielectric constant of a transmission line material

a. Inductance and capacitanceb. Velocity factorc. Characteristic impedanced. Propagation velocity38. To couple a coaxial line to a parallel-wire line, it is best to use aa. Slotted lineb. Balunc. Directional couplerd. Quarter-wave transformer39. Transmission line consisting of two conductors that have equal resistance per unit length.a. Unbalanced line

b. Open-wire line

c. Balanced line

d. Coaxial line

40. For maximum absorption of power at the antenna, the relationship between the characteristic impedance of the line Zo and the load impedance Zl should bea. Zo = ZLb. Zo > Zlc. Zo < Zld. Zo = 0

41. In the study of transmission cable, twin lead is also referred to as a __________.a. Twisted pair

b. Double cable

c. Ribbon cable

d. Open pair

42. A ratio expressing the percentage of incident voltage reflected on a transmission line is known as thea. Velocity factor

b. Standing-wave ratio

c. Reflection coefficient

d. Line efficiency

43. An open quarter-wave line at the operating frequency acts like a(n)

a. Series resonant circuit

b. Parallel resonant circuit

c. Capacitor

d. Inductor

44. At UHF and microwave frequencies, transmission lines are commonly used asa. Antennab. Couplerc. Resonant circuitd. Transformer45. Transmission line is a two-wire cable that connects the transmitter to the antenna or the antenna to the receiver. The purpose of the transmission line is toa. Amplify the RF signal

b. Modulate the signal

c. Carry the RF energy for the desired distance

d. All of the above

46. 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 cable

b. Open-wire transmission lines

c. Optical cables

d. Waveguides

47. The characteristic impedance of a transmission line is determined by:a. Its operating frequencyb. Its lengthc. Its physical size and arrangementd. The signal applied at the input terminal48. Shunt capacitance was determined due to:a. Conductors were closed to each other

b. The length and diameter of the conductors

c. Dielectric losses

d. Flux linkages

49. 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. Both B and C

50. If a change in the dielectric material decreases the capacitance, the characteristic impedance isa. Kept constant

b. Decreased

c. Increased

d. halved

5