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ITC Exam 2021 > NAVEDTRA 14182A Module 10 Chapter 2 > Flashcards

NAVEDTRA 14182A Module 10 Chapter 2 Flashcards

1
Q

Which two composite fields (composed of E and H fields) are associated with every
antenna?

A

Induction field and radiation field

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2
Q

What composite field (composed of E and H fields) is found stored in the antenna?

A

Induction field

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3
Q

What composite field (composed of E and H fields) is propagated into free space?

A

Radiation field

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4
Q

What is the term used to describe the basic frequency of a radio wave?

A

Fundamental frequency

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5
Q

What is the term used to describe a whole number multiple of the basic frequency of
a radio wave?

A

Harmonic frequency or harmonics

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6
Q

It is known that WWV operates on a frequency of 10 megahertz. What is the
wavelength of WWV?

A

30 meters

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7
Q

A station is known to operate at 60-meters. What is the frequency of the unknown
station?

A

5 MHz

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8
Q

If a transmitting antenna is placed close to the ground, how should the antenna be
polarized to give the greatest signal strength?

A

Vertically polarized

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9
Q

In the right-hand rule for propagation, the thumb points in the direction of the E field
and the forefinger points in the direction of the H field. In what direction does the middle finger point?

A

Direction of wave propagation

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10
Q

What is one of the major reasons for the fading of radio waves which have been
reflected from a surface?

A

Shifting in the phase relationships of the wave

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11
Q

What are the three layers of the atmosphere?

A

Troposphere, stratosphere, and ionosphere

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12
Q

Which layer of the atmosphere has relatively little effect on radio waves?

A

Stratosphere

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13
Q

What is the determining factor in classifying whether a radio wave is a ground wave or a space wave?

A

Whether the component of the wave is travelling along the surface or over the surface of the earth

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14
Q

What is the best type of surface or terrain to use for radio wave transmission?

A

Sea water

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15
Q

What is the primary difference between the radio horizon and the natural horizon?

A

Radio horizon is about 1/3 farther

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16
Q

What three factors must be considered in the transmission of a surface wave to
reduce attenuation?

A

(a) electrical properties of the terrain (b) frequency (c) polarization of the
antenna

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17
Q

What causes ionization to occur in the ionosphere?

A

High energy ultraviolet light waves from the sun

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18
Q

How are the four distinct layers of the ionosphere designated?

A

D, E, F1, and F2 layers

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19
Q

What is the height of the individual layers of the ionosphere?

A

D layer is 30-55 miles, E layer 55-90 miles, and F layers are 90-240 miles

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20
Q

What factor determines whether a radio wave is reflected or refracted by the
ionosphere?

A

Thickness of ionized layer

21
Q

There is a maximum frequency at which vertically transmitted radio waves can be
refracted back to Earth. What is this maximum frequency called?

A

Critical frequency

22
Q

What three main factors determine the amount of refraction in the ionosphere?

A

(a) density of ionization of the layer (b) frequency (c) angle at which it enters the
layer

23
Q

What is the skip zone of a radio wave?

A

A zone of silence between the ground wave and sky wave where there is no
reception

24
Q

Where does the greatest amount of ionospheric absorption occur in the ionosphere?

A

Where ionization density is greatest

25
Q

What is meant by the term “multipath”?

A

A term used to describe the multiple pattern a radio wave may follow

26
Q

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

A

Selective fading

27
Q

What are the two main sources of EMI with which radio waves must compete?

A

Natural and man-made interference

28
Q

Thunderstorms, snowstorms, cosmic sources, the sun, etc., are a few examples of
EMI sources. What type of EMI comes from these sources?

A

Natural

29
Q

Motors, switches, voltage regulators, generators, etc., are a few examples of EMI
sources. What type of EMI comes from these sources?

A

Man-made

30
Q

What are three ways of controlling the amount of transmitter-generated EMI?

A

(a) filtering and shielding of the transmitter (b) limiting bandwidth (c) cutting the
antenna to the correct frequency

31
Q

What are three ways of controlling radiated EMI during transmission?

A

(a) physical separation of the antenna (b) limiting bandwidth of the antenna (c)
use of directional antennas

32
Q

What are the two general types of variations in the ionosphere?

A

Regular and irregular variations

33
Q

What is the main difference between these two types of variations?

A

Regular variations can be predicted but irregular variations are unpredictable

34
Q

What are the four main classes of regular variation which affect the extent of
ionization in the ionosphere?

A

Daily, seasonal, 11-year, and 27-days variation

35
Q

What are the three more common types of irregular variations in the ionosphere?

A

Sporadic E, sudden disturbances, and ionospheric storms

36
Q

What do the letters muf, luf, and fot stand for?

A

Muf is maximum usable frequency. Luf is lowest usable frequency. Fot is
commonly known as optimum working frequency.

37
Q

When is muf at its highest and why?

A

Muf is highest around noon. Ultraviolet light waves from the sun are most
intense

38
Q

What happens to the radio wave if the luf is too low?

A

When luf is too low it is absorbed and is too weak for reception

39
Q

What are some disadvantages of operating transmitters at or near the luf?

A

Signal-to-noise ratio is low and the probability of multipath propagation is
greater

40
Q

What are some disadvantages of operating a transmitter at or near the muf?

A

Frequent signal fading and dropouts

41
Q

What is fot?

A

Fot is the most practical operating frequency that can be relied on to avoid
problems of multipath, absorbtion, and noise

42
Q

How do raindrops affect radio waves?

A

They can cause attenuation by scattering

43
Q

How does fog affect radio waves at frequencies above 2 gigahertz?

A

It can cause attenuation by absorbtion

44
Q

How is the term “temperature inversion” used when referring to radio waves?

A

It is a condition where layers of warm air are formed above layers of cool air

45
Q

How does temperature inversion affect radio transmission?

A

It can cause vhf and uhf transmission to be propagated far beyond normal line-of-sight distances

46
Q

In what layer of the atmosphere does virtually all weather phenomena occur?

A

Troposphere

47
Q

Which radio frequency bands use the tropospheric scattering principle for
propagation of radio waves?

A

Vhf and above

48
Q

Where is the tropospheric region that contributes most strongly to tropospheric
scatter propagation?

A

Near the mid-point between the transmitting and receiving antennas, just above the radio horizon

ITC Exam 2021 (36 decks)

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