Wave Propagation

1. The polarization of an electromagnetic wave is determined by the direction of:

A. B field

B. H field

C. E field

D. All of the choices

2. The diffraction process allows reception beyond a mountain in all but a small area known as:

A. Dead zone

B. Shadow zone

C. masking

D. Open space

3. A term used to describe variations in signal strength that occur at a receiver during the time a signal is being received is known as:

A. skipping

B. refraction

C. bouncing

D. fading

4. An electronic system performing the reception, frequency translation, and retransmission is called a:

A. TRF

B. superheterodyne

C. satellite

D. transponder

5. Another term for groundwave is:

A. Space wave

B. Sky wave

C. Surface wave

D. Direct wave

6. A device that converts electrical energy into electromagnetic energy is known as

A. A light bulb

B. An antenna

C. A transducer

D. All of the choices

7. The characteristic impedance of free space is:

A. 50 ohms

B. 75 ohms

C. 300 ohms

D. 377 ohms

8. The bending of electromagnetic waves due to its passing through regions of different densities is known as:

A. radiation

B. reflection

C. refraction

D. diffraction

9. The type of wave that is limited to line-of-sight transmission distances is:

A. Ground wave

B. Space wave

C. Sky wave

D. All of the choices

10. RFI is:

A. polarization

B. reactive

C. radiofrequency Interference

D. All of the above

11. A point in space that radiates equally in all directions is:

A. Parabolic reflector

B. isotropic Point source

C. Electromagnetic wave

D. An antenna

12. The term for the case when the same signal arrives at the TV receiver at the two different times is:

A. ghosting

B. phasing

C. tagging

D. pulsing

13. The constant temperature stratosphere is also called the:

A. ionosphere

B. perisphere

C. Sunspot region

D. None of the choices

14. The highest frequency transmitted vertically under given ionosphere conditions that will be returned to the earth is called the:

A. Reflected frequency

B. Damped frequency

C. Critical angle

D. Critical frequency

15. Between the point where the ground wave is completely dissipated and the point where the fist sky wave returns is called:

quiet zone
skip zone
fading

A. A only

B. B only

C. both A and D

D. both A and B

16. What is used to accommodate severe fading problems?

A. Space diversity

B. Frequency diversity

C. Angle diversity

D. Diversity reception

17. Which term applies to troposcatter propagation:

A. SIDs

B. Fading

C. Atmospheric storms

D. Miller effect

18. For some type of services, VLF waves are used because:

A. They provide faster transmission rate

B. The transmitting antennas are of convenient size

C. They are very reliable

D. The penetrate the ionosphere easily

19. Which is not used for beyond-the-horizon terrestrial communications without the use of repeaters:

A. 350 kHz

B. 150 MHz

C. 60 Hz

D. 12 GHz

20. High-frequency waves are

A. Absorbed by the F1 layer

B. Reflected by the D layer

C. Are also called microwaves

D. Affected by the solar cycle

21. Why the distance near the skip distance does is used for the sky-wave propagation?

A. To avoid tilting

B. To prevent sky-wave and upper ray interference

C. To avoid the Faraday effect

D. To avoid super-refraction

22. A ship-to-ship communications system is plagued by fading. The best solution seems to be use of

A. A more directional antenna

B. An antenna with wide bandwidth

C. Frequency diversity

D. Space diversity

23. A term used for a specific range of microwave frequencies more easily passed by the atmosphere compared to others:

A. window

B. Critical frequency

C. bandwidth

D. Resonance in the atmosphere

24. Frequencies in the UHF range normally propagate by means of

A. Ground waves

B. Sky waves

C. Vertically polarized waves

D. Space waves

25. Tropospheric scatter or troposcatter is used with frequencies in what spectrum?

A. HF

B. VHF

C. UHF

D. SHF

26. The ground wave eventually disappears, as the distance gets longer from the transmitter. This is due to:

A. Interference from the sky wave

B. Loss of line-of-sight conditions

C. Faraday’s rotation

D. tilting

27. Polarization of electromagnetic waves:

A. Is caused by reflection

B. Is due to the transverse nature of the waves

C. Results from the longitudinal nature of the waves

D. Is either horizontal or vertical only

28. Which of the following is the only thing that can happen when an electromagnetic waves travel in free space?

A. absorption

B. attenuation

C. refraction

D. diffraction

29. Absorption of electromagnetic waves by the atmosphere depends on

A. Their frequency

B. Their distance from the transmitter

C. The polarization of the waves

D. Impedance of the antenna feed point

30. Refraction of electromagnetic waves happens when:

A. The signal passes into a medium of different

B. The signals are polarized at right angles to the direction of propagation

C. The signal encounters a perfect conducting plane

D. The signal passes through an edge of an object

31. Diffraction of electromagnetic waves:

A. Will happen if the critical angle is smaller than the incident angle

B. Arises only with spherical wavefronts

C. Will occur when the waves pass through a large slot

D. May occur around the edge of a sharp obstacle

32. A microwave signal following the curvature of the earth:

A. Faraday effect

B. ducting

C. tilting

D. Ionospheric reflection

33. Helical antennas are good for satellite tracking at VHF due to:

A. troposcatter

B. Its horizontal polarization

C. Ionospheric refraction

D. the Faraday effect

34. Radio waves were first predicted mathematically by:

A. Armstrong

B. Hertz

C. Maxwell

D. Marconi

35. Radio waves were first demonstrated experimentally by:

A. Armstrong

B. Hertz

C. Maxwell

D. Marconi

36. Which of the following are electromagnetic:

A. Radio waves

B. light

C. Gamma waves

D. All of the choices

37. The electric and magnetic fields of a radio wave are:

A. Perpendicular to each other

B. Perpendicular to the direction of travel

C. Both perpendicular to each other and to the direction of travel

D. None of the choices

38. TEM stands for:

A. Transverse Electromagnetic

B. Transmitted Electromagnetic

C. True Electromagnetic

D. None of the choices

39. In free space, radio waves travel at a speed of:

A. 3 x 10^6 meters per second

B. 300 x 10^6 meters per second

C. 3 x 10^6 miles per second

D. 300 x 10^6 miles per second

40. Which is a possible polarization for an electromagnetic wave:

A. vertical

B. horizontal

C. circular

D. All of the choices

41. Which polarization can be reasonably well received by a circularly polarized antenna:

A. vertical

B. horizontal

C. circular

D. All of the choices

42. The number of circular polarization modes (directions) is:

A. 1

B. 2

C. 3

D. many

43. An antenna has "gain" as compared to:

A. An isotropic radiator

B. A vertically polarized radiator

C. A ground-wave antenna

D. None of the choices

44. EIRP stands for:

A. the E and I fields of the Radiated Power

B. the Effective Isotropic Radiated Power

C. the Effective Internal Reflected Power

D. the Electric-field Intensity of the Radiated Power

45. The "attenuation of free space" is due to:

A. Losses in the characteristic impedance of free space

B. Losses due to absorption in the upper atmosphere

C. The decrease in energy per square meter due to expansion of the wavefront

D. The decrease in energy per square meter due to absorption of the wavefront

46. Ground waves are most effective:

A. Below about 2 MHz

B. Above about 20 MHz

C. At microwave frequencies

D. When using horizontally polarized waves

47. Radio waves would most strongly reflect off:

A. A flat insulating surface of the right size

B. A flat dielectric surface of the right size

C. A flat metallic surface of the right size

D. A flat body of water

48. Radio waves sometimes "bend" around a corner because of:

A. reflection

B. diffusion

C. refraction

D. diffraction

49. Space waves are:

A. line-of-sight

B. Reflected off the ionosphere

C. Same as sky waves

D. Radio waves used for satellite communications

50. Sky waves:

A. Are line-of-sight

B. "bounce" off the ionosphere

C. Are same as space waves

D. Are radio waves used for satellite communications

51. Sky waves cannot be "heard":

A. Close to the transmitter

B. Far from the transmitter

C. In the "silent" zone

D. In the "skip" zone

52. A 20-dB reduction in the strength of a radio wave due to reflection is called:

A. fading

B. diffraction

C. Frequency diversity

D. Spatial diversity

53. "Ghosts" on a TV screen are an example of:

A. fading

B. diffraction

C. Multipath distortion

D. Cancellation due to reflection

54. A "repeater" is used to:

A. Send a message multiple times over a channel

B. Send a message over multiple channels at the same time

C. Extend the range of a radio communications system

D. Cancel the effects of fading

55. The troposphere is the:

A. Highest layer of the atmosphere

B. Middle layer of the atmosphere

C. Lowest layer of the atmosphere

D. The most ionized layer of the atmosphere

56. Meteor-trail propagation is:

A. Used for radio telephony

B. Used to send data by radio

C. Also called "ducting"

D. Not possible

57. If a transmitting antenna is 350 ft high and the receiving antenna is 25 ft high, the longest practical transmission distance is:

A. 33.5 km

B. 33.5 mi

C. 97.7 km

D. 97.7 mi

58. A 275-ft-high transmitting antenna has a gain of 12 dB over a dipole. The receiving antenna, which is 60 ft high, has a gain of 3 dB. The transmitter power is 100 W at 224 MHz. Calculate the maximum transmitting distance.

A. 34.4 km

B. 55.4 km

C. 100 mi

D. 100 km

59. For antennas that are 100 ft high, the minimum spacing would be:

A. 9.09 m

B. 1,100 m

C. 9.09 ft

D. 1,100 ft

60. Find the characteristics impedance of polyethylene.

A. 377 Ω

B. 75 Ω

C. 249 Ω

D. 135 Ω

61. Find the characteristics impedance of glass, which has a relative permittivity of 7.8.

A. 377 Ω Ω

B. 75 Ω

C. 249

D. 135 Ω

63. Calculate the electric field intensity.

A. 2.56 x 10^-3 V/m

B. 5.36 x 10^-3 V/m

C. 6.53 x 10^-3 V/m

D. 3.65 x 10^-3 V/m

Use the statement below to answer the next 3 items. An isotropic source radiates 100 W of power in free space. Consider a distance 15 km from the source.

62. Calculate the power density.

A. 55.33 x 10^-9 W/m^2

B. 75.21 x 10^-9 W/m^2

C. 35.36 x 10^-9 W/m^2

D. 11.34 x 10^-9 W/m^2

64. Calculate the magnetic field intensity.

A. 9.68 x 10^-6 A/m

B. 6.98 x 10^-6 A/m

C. 3.45 x 10^-6 A/m

D. 4.35 x 10^-6 A/m

65. What power density is required to produce an electric field strength of 100 volts per meter in air?

A. 26.5 mW/m^2

B. 26.5 W/m^2

C. 6.52 mW/m^2

D. 6.52 W/m^2

66. What power density is required to produce a magnetic field strength of 0.814 A per meter in air?

A. 250 mW/m^2

B. 250 W/m^2

C. 100 mW/m^2

D. 100 W/m^2

67. A radio wave moves from air (εr= 1) to glass (εr= 7.8). Its angle of incidence is 30 deg. What is the angle of refraction?

A. 11.56 deg

B. 46.77 deg

C. 10.2 deg

D. 30 deg

68. A radio wave moves from glass (εr= 7.8) to air (εr= 1) to. Its angle of incidence is 30 deg. What is the angle of refraction?

A. 11.56 deg

B. 46.77 deg

C. 10.2 deg

D. 30 deg

Use the statement below to answer the next 2 questions. The critical frequency at a particular time 11.6 MHz and the required angle of incidence for propagation to a desired destination if 70 deg.

What is the MUF for a transmitting station?

A. 29 MHz

B. 34 MHz

C. 27 MHz

D. 31 MHz

70. What is the OWF for a transmitting station?

A. 29 MHz

B. 34 MHz

C. 27 MHz

D. 31 MHz

A taxi company uses a central dispatcher, with an antenna at the top of a 15 m tower, to communicate with taxi cabs. The taxi antennas are on the roofs of the cars, approximately 1.5 m above the ground.

Calculate the maximum communication distance between

the dispatcher and a taxi.

A. 10.1 km

B. 5.43 km

C. 21 km

D. 32 km

72. Calculate the maximum communication distance between two taxis.

A. 10.1 km

B. 5.43 km

C. 21 km

D. 32 km

73. Calculate the maximum communication distance between two company dispatchers assuming both have the same tower height.

A. 10.1 km

B. 5.43 km

C. 21 km

D. 32 km

An automobile travels at 60 km/hr.

74. Find the time between fades if the car uses a cellphone at 800 MHz.

A. 44.56 ms

B. 3.34 ms

C. 11.25 ms

D. 4.7 ms

75. Find the time between fades if the car uses a PCS phone at 1900 MHz.

A. 44.56 ms

B. 3.34 ms

C. 11.25 ms

D. 4.7 ms

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