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March 2017 E-6 IT1 Exam > NAVEDTRA 14182A, Ch. 2 > Flashcards

NAVEDTRA 14182A, Ch. 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 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 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 a eight 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

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 the two principal 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

Which frequency band is used for sky wave propagation?

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 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?

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 variation 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 ionization in the ionosphere

be divided into?

A

Four

43
Q

What are responsible for 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 turbulence’s?

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

March 2017 E-6 IT1 Exam (83 decks)

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