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ITC EXAM 2019 > NAVEDTRA 14182A, NAVY ELECTRICITY AND ELECTRONICS TRAINING SERIES MODULE 10-WAVE PROPAGATION, TRANSMISSION LINES, AND ANTENNAS > Flashcards

NAVEDTRA 14182A, NAVY ELECTRICITY AND ELECTRONICS TRAINING SERIES MODULE 10-WAVE PROPAGATION, TRANSMISSION LINES, AND ANTENNAS Flashcards

1
Q

Which two basic fields are associated with every antenna?

A

Induction and Radiation

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2
Q

Which field is associated with energy stored in the antenna?

A

Induction

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3
Q

Which type of antenna has an electrical length equal to half the wavelength of the signal being transmitted?

A

Half-wave

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4
Q

What is an energy wave called that is generated by a transmitter?

A

Radio wave

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5
Q

What is the basic shape of the wave generated by a transmitter?

A

Sine wave

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6
Q

What is the number of cycles of a sine wave that are completed in 1 second known as?

A

Frequency

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7
Q

The frequencies falling between 3 kHz and what are called radio frequencies (abbreviated rf) since they are commonly used in radio communications?

A

300 GHz

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8
Q

The usable radio-frequency range is roughly 10 kilohertz to what?

A

100 gigahertz

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9
Q

What is the VLF frequency range?

A

3 to 30 KHz

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10
Q

What is the LF frequency range?

A

30 to 300 KHZ

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11
Q

What is the MF frequency range?

A

300 to 3000KHz

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12
Q

What is the HF frequency range?

A

3 to 30 MHz

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13
Q

What is the VHF frequency range?

A

30-300 MHz

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14
Q

What is the UHF frequency range?

A

300 to 3000 MHz

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15
Q

What is the SHF frequency range?

A

3 to 30 GHz

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16
Q

What is the EHF frequency range?

A

30 to 300 GHz

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17
Q

Any frequency that is a whole number multiple of a smaller basic frequency is known as what property of that basic frequency?

A

Harmonic

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18
Q

What is the property of a radio wave which is simply the amount of time required for the completion of one full cycle?

A

Period

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19
Q

What is the space called occupied by one full cycle of a radio wave at any given instant?

A

Wave length

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20
Q

The velocity (or speed) of a radio wave radiated into free space by a transmitting antenna is equal to the speed of light - which is how many miles per second?

A

186,000

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21
Q

Where must the receiving antenna be located for a maximum absorption of energy from the electromagnetic fields?

A

Plane of polarization

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22
Q

Troposphere, Stratosphere, along with what else are the three separate regions, or layers that the Earth’s atmosphere is divided into?

A

Ionosphere

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23
Q

The troposphere is the portion of the Earth’s atmosphere that extends from the surface of the Earth to a height of about 3.7 miles (6 km) at the North Pole or the South Pole and how many miles at the equator?

A

11.2

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24
Q

Which atmosphere layer has relatively little effect on radio waves because it is a relatively calm region with little or no temperature changes?

A

Stratosphere

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25
Q

The Ionosphere extends upward from about 31.1 miles to a height of about how many miles?

A

250

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26
Q

What is the most important region of the atmosphere for long distance point-to-point communications?

A

Ionosphere

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27
Q

What are the two principal ways in which electromagnetic (radio) energy travels from a transmitting antenna to a receiving antenna?

A

Ground and Sky waves

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28
Q

The surface wave is impractical for long distance transmissions at frequencies above what frequency?

A

2 megahertz

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29
Q

Which frequency band is used for sky wave propagation?

A

High Frequency (HF)

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30
Q

What is the process known as of upsetting electrical neutrality?

A

Ionization

31
Q

What occurs when the free electrons and positive ions collide with each other?

A

Recombination

32
Q

How many layers is the Ionosphere composed of?

33
Q

Each ionospheric layer has a maximum frequency at which radio waves can be transmitted vertically and refracted back to Earth which is known as what?

A

Critical frequency

34
Q

What is the distance from the transmitter to the point where the sky wave is first returned to Earth?

A

Skip distance

35
Q

What results in the loss of energy of a radio wave and has a pronounced effect both on the strength of received signals and the ability to communicate over long distances?

A

Absorption

36
Q

Fading on ionospheric circuits is mainly a result of what?

A

Multipath propagation

37
Q

In what practice are two transmitters and two receivers used, each pair tuned to a different frequency, with the same information being transmitted simultaneously over both frequencies?

A

Frequency diversity

38
Q

When a wide band of frequencies is transmitted simultaneously, each frequency will vary in the amount of fading. What is this variation called?

A

Selective fading

39
Q

The combined effects of absorption, ground reflection loss, and what else account for most of the energy losses of radio transmissions propagated by the ionosphere?

A

Free space loss

40
Q

There is little natural interference above what frequency?

A

30 megahertz

41
Q

What is a zone of silence between the point where the ground wave becomes too weak for reception and the point where the sky wave is first returned to Earth?

42
Q

How many main classes can the regular variations that affect the extent of ionization in the ionosphere be divided into?

43
Q

What are responsible for variations in the ionization level of the ionosphere?

44
Q

Long distance propagation of hf radio waves is almost totally “blanked out” when what occurs?

A

Sudden Ionospheric Disturbance (SID)

45
Q

An ionospheric storm that is associated with sunspot activity may begin anytime from 2 days before an active sunspot crosses the central meridian of the sun until how many days after it passes the central meridian?

46
Q

For a given angle of incidence and time of day, there is a maximum frequency that can be used for communications between two given locations. What is the frequency known as?

A

Maximum Usable Frequency (MUF)

47
Q

Raindrops cause greater attenuation by scattering than by absorption at frequencies above what?

A

100 megahertz

48
Q

Fog can cause serious attenuation by absorption at frequencies above what?

A

2 gigahertz

49
Q

What is the condition when layers of warm air are formed above layers of cool air known as?

A

Temperature inversion

50
Q

As the lowest region of the Earth’s atmosphere, the troposphere extends from the Earth’s surface to a height of slightly over how many miles?

51
Q

What region does virtually all weather phenomena occur in?

A

Troposphere

52
Q

Radio waves of frequencies below what normally have wavelengths longer than the size of weather turbulences?

A

30 megahertz

53
Q

The usable frequency range for tropospheric scattering is from about 100 megahertz to what?

A

10 gigahertz

54
Q

A correctly designed tropospheric scattering is from about 100 megahertz to what?

A

10 gigahertz

55
Q

A correctly designed tropospheric scatter circuit will provide highly reliable service for distances ranging from 50 miles to how many miles?

56
Q

Which device is designed to guide electrical energy from one point to another?

A

Transmission line

57
Q

Which type of line consists of two insulated wires twisted together to form a flexible line without the use of spacers?

A

Twisted pair

58
Q

Leakage caused by the condensation of moisture is prevented in some rigid line applications by the use of what?

59
Q

What was developed to replace rubber and eliminate high-frequency losses associated with rubber insulators?

A

Polyethylene plastic

60
Q

The radius of bends in the wavelength must measure greater than how many wavelengths at the operating frequency of the equipment to avoid excessive attenuation?

61
Q

Line losses may be any of three types-Radiation/induction, Dielectric, and what else?

62
Q

Copper losses can be minimized and conductivity increased in an RF line by plating the line with what?

63
Q

Which type of losses occur because some magnetic lines of force about a conductor do not return to the conductor when the cycle alternates?

64
Q

What determines the amount of current that can flow when a given voltage is applied to an infinitely long line?

A

Characteristic impedance

65
Q

The characteristic impedance of lines in actual use normally lies between 50 and how many ohms?

66
Q

When a transmission line is “short” compared to the length of the radio-frequency waves it carries, the opposition presented to the input terminals is determined primarily by what?

A

Load impedance

67
Q

If a line is not terminated in characteristic impedance, what is it said to be?

68
Q

What are voltages called that are moving toward the receiving end of a line?

A

Incident voltages

69
Q

Which type of line has no standing waves of current and voltage?

A

Nonresonant

70
Q

Which type of line has a finite length and is not terminated in its characteristic impedance?

71
Q

What is the maximum voltage to minimum voltage on a line called?

72
Q

What are hollow metal tubes used to transfer energy from one point to another?

A

Waveguides

73
Q

What are theoretical properties (inductance, resistance, and capacitance) of a transmission line that are lumped into a single component?

A

Lumped constants

ITC EXAM 2019 (18 decks)

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