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Substitute Exam 2024 > NAVEDTRA 14182A Chapter 2 > Flashcards

NAVEDTRA 14182A Chapter 2 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 the 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 wave length 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 a 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 one second known as?

A

Frequency

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7
Q

The frequencies falling between 3kHz 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 3000 KHz

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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 to 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

Wavelength

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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 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

23
Q

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

A

11.2

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

25
Q

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

A

250

26
Q

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

A

Ionosphere

27
Q

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

A

Ground and sky waves

28
Q

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

A

2 megahertz

29
Q

Which frequency band is used for sky wave propagation?

A

High frequency

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?

A

Three

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 is the 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?

A

Skip Zone

36
Q

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

A

Absorption

37
Q

Fading on ionospheric circuits is mainly a result of what?

A

Multipath propagation

38
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

39
Q

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

A

Selective fading

40
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

41
Q

There is little natural interference above what frequency?

A

30 megahertz

42
Q

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

A

Four

43
Q

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

A

Sunspots

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?

A

Four

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 this 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?

A

7

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

A

500

Substitute Exam 2024 (12 decks)

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