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IT1 SEP EXAM 2018 > 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 term means “movement through a medium”

A

Propagation

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2
Q

What can be defined as a disturbance (sound, light, radio waves) that moves through a medium (air, water, vacuum)?

A

Wave

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3
Q

What can be defined as a reoccurring disturbance advancing through space with or without the use of a physical medium?

A

Wave motion

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4
Q

Which type of waves are water waves known as because the motion of the water is up and down, or at right angles to the direction in which the waves are traveling?

A

Transverse

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5
Q

Which type of waves are waves in which the disturbance takes place in the direction of propagation?

A

Longitudinal

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6
Q

What is the vehicle through which the wave travels from one point to the next?

A

Medium

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7
Q

What is the position called that a particle of matter would have if it were not disturbed by wave motion?

A

Reference line

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8
Q

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

A

Wavelength

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9
Q

Which unit of measurement are wavelengths expressed in?

A

Meters

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10
Q

Which wave property gives a relative indication of the amount of energy the wave transmits?

A

Amplitude

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11
Q

What is a continuous series of waves called having the same amplitude and wavelength?

A

Wave train

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12
Q

The number of vibrations, or cycles, of a wave train in a unit of time is called the reequency of the wave train and is measured in what?

A

Hertz

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13
Q

Which term refers to the number of occurrences that take place in one second?

A

Hertz

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14
Q

Which propagation property is the rate at which the disturbance travels through the medium, or the velocity with which the crest of the wave moves along?

A

Velocity

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15
Q

What is the time in which one complete vibratory cycle of events occurs?

A

Period

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16
Q

What is a wave called that is directed toward the surface of the mirror?

A

Incident

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17
Q

What is the angle between the reflected wave and the normal called?

A

Angle of reflection

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18
Q

Which law states that “the angle of incidence is equal to the angle of reflection”?

A

Law of reflection

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19
Q

What is the bending of the wave path when the waves meet an obstruction?

A

Diffraction

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20
Q

What is the apparent change in frequency or pitch when a sound source moves either toward or away from the listener, or when the listener moves either toward or away from the sound source?

A

Doppler Effect

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21
Q

How does sound travel through a medium?

A

Wave motion

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22
Q

In the study of physics, what is defined as a range of compression-wave frequencies to which the human ear is sensitive?

A

Sound

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23
Q

Which type of sounds are capable of being heard by the human ear?

A

Sonics

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24
Q

The Navy has set an arbitrary upper limit for sonics at 10,000 hertz and a lower limit at what?

A

15 hertz

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25
Q

What is it standard practice to refer to sounds above 10,000 hertz as?

A

Ultrasonic

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26
Q

What are sounds below 15 hertz known as?

A

Infrasonic

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27
Q

How many basic elements for transmission and reception of sound must be present before a sound can be produced?

A

Three

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28
Q

Which two general groups may sounds be broadly classified into?

A

Noise or Tones

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29
Q

Sound has three basic characteristics: pitch, intensity, and what else?

A

Quality

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30
Q

Which term is used to describe the frequency of a sound?

A

Pitch

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31
Q

What is a measure of the sound energy of a wave?

A

Intensity

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32
Q

What is the sensation the intensity (and sometimes frequency) the sound wave produces on the ear?

A

Loudness

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33
Q

What are the two basic physical properties that govern the velocity of sound through the medium?

A

Elasticity and Density

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34
Q

What is the ability of a strained body to recover its shape after deformation?

A

Elasticity

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35
Q

What property of a medium or substance is the mass per unit volume of the medium or substance?

A

Density

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36
Q

What is the velocity in FPS that sound will travel through air at 32 degrees F?

A

1,087

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37
Q

What is the science of sound referred to as?

A

Acoustics

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38
Q

What is the reflection of the original sound wave as it bounces off a distant surface called?

A

Echo

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39
Q

In empty rooms or other confined spaces, sound may be reflected several times to cause what is known as what?

A

Reverberation

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40
Q

What is any disturbance, man-made or natural, that causes an undesirable response or the degradation of a wave referred to as?

A

Interference

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41
Q

What is the most complex sound wave that can be produced?

A

Noise

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42
Q

What is light a form of?

A

Electromagnetic radiation

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43
Q

Current light theory says that light is made up of very small packets of electromagnetic energy called what?

A

Photons

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44
Q

Approximately how many miles per second does light travel?

A

186,000

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45
Q

What is a large volume of light called?

A

Beam

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46
Q

What is a narrow volume of light called?

A

Pencil

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47
Q

Which type of substance is one through which you can see clearly?

A

Transparent

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48
Q

What are substances called through which some light rays can pass but through which objects cannot be seen clearly because the rays are diffused?

A

Translucent

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49
Q

Which year did Ole Roemer discover that light travels approximately 186,000 miles per second in space?

A

1675

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50
Q

How many times in one second can a light beam circle the earth?

A

7.5

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51
Q

Which term is used to designate the entire range of electromagnetic waves arranged in order of their frequencies?

A

Spectrum

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52
Q

What is a conductor or a set of conductors used either to radiate electromagnetic energy into space or to collect this energy from space?

A

Antenna

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53
Q

Which two primary components does an electromagnetic wave consist of?

A

Electric and Magnetic field

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54
Q

What is the smallest unit of radiant energy that makes up light waves and radio waves?

A

Photon

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55
Q

Which units are used for measuring the wavelength of light?

A

Angstrom

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56
Q

What are the primary colors of light?

A

Red, Green, and blue

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57
Q

What are the complementary colors of light?

A

Magenta, yellow, cyan

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58
Q

Which two basic fields are associated with every antenna?

A

Induction and radiation

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59
Q

Which field is associated with the energy stored in the antenna?

A

Induction

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60
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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61
Q

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

A

Radio wave

62
Q

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

A

Sine wave

63
Q

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

A

Frequency

64
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

65
Q

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

A

100 gigahertz

66
Q

What is the VLF frequency range?

A

3 to 30 KHz

67
Q

What is the LF frequency range?

A

30 to 300 KHz

68
Q

What is the MF frequency range?

A

300 to 3000 KHz

69
Q

What is the HF frequency range?

A

3 to 30 MHz

70
Q

What is the VHF frequency range?

A

30 to 300 MHz

71
Q

What is the UHF frequency range?

A

300 to 3000 MHz

72
Q

What is the SHF frequency range?

A

3 to 30 GHz

73
Q

What is the EHF frequency range?

A

30 to 300 GHz

74
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

75
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

76
Q

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

A

Wavelength

77
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

78
Q

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

A

Plane of polarization

79
Q

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

A

Ionosphere

80
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

81
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

82
Q

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

A

250

83
Q

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

A

Ionosphere

84
Q

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

A

Ground and Sky waves

85
Q

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

A

2 megahertz

86
Q

Which frequency band is used for sky wave propagation?

A

High Frequency (HF)

87
Q

What is the process known as of upsetting electrical neutrality?

A

Ionization

88
Q

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

A

Recombination

89
Q

How many layers is the Ionosphere composed of?

A

Three

90
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

91
Q

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

A

Skip distance

92
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

93
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

94
Q

Fading on ionospheric circuits is mainly a result of what?

A

Multipath propagation

95
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

96
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

97
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

98
Q

There is little natural interference above what frequency?

A

30 megahertz

99
Q

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

A

Four

100
Q

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

A

Sunspots

101
Q

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

A

Sudden Ionospheric Disturbance (SID)

102
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

103
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)

104
Q

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

A

100 megahertz

105
Q

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

A

2 gigahertz

106
Q

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

A

Temperature inversion

107
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

108
Q

What region does virtually all weather phenomena occur in?

A

Troposphere

109
Q

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

A

30 megahertz

110
Q

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

A

10 gigahertz

111
Q

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

A

500

112
Q

Which two basic classifications are most practical transmitting antennas divided into?

A

Hertz and Marconi

113
Q

Which type of antennas operate with one end grounded and are mounted perpendicular to the Earth or to a surface acting as a ground?

A

Marconi

114
Q

Hertz antennas are generally used for frequencies above what?

A

2 megahertz

115
Q

Which three parts does a complete antenna system consist of?

A

Coupling device, feeder, and antenna

116
Q

What is defined as a conductor or group of conductors used either for radiating electromagnetic energy into space or for collecting it from space?

A

Antenna

117
Q

What is the interchangeability of the same antenna for transmitting and receiving known as?

A

Reciprocity

118
Q

What cannot be used at medium and low frequencies because the electric lines of force are parallel to and touch the earth?

A

Horizontal polarization

119
Q

Which frequencies is sky-wave transmission used?

A

High

120
Q

From approximately 50 to how many megahertz, vertical polarization results in a slightly stronger signal than does horizontal polarization with antennas at the same height?

A

100

121
Q

At 30 megahertz, vertical polarization is better for antenna heights below about how many meters?

A

91

122
Q

At ordinary antenna mast heights of 12 meters (40 feet), vertical polarization is advantageous for frequencies less than about what?

A

100 megahertz

123
Q

Which type of polarization is used by VHF and UHF transmissions?

A

Horizontal

124
Q

What is the useful part of the transmitter’s signal?

A

Radiated energy

125
Q

For the antenna in free space, that is, entirely removed from any objects that might affect its operation, the radiation resistance is how many ohms?

A

73

126
Q

For most half-wave wire antennas, the radiation resistance is about how many ohms?

A

65

127
Q

What is a plot of the radiated energy from an antenna?

A

Radiation pattern

128
Q

What is it known as when antenna sources radiate energy equally in all directions?

A

Isotropic radiation

129
Q

Which type of radiators emit (radiate) stronger radiation in one direction than in another?

A

Anisotropic

130
Q

What is used to indicate directions of minimum radiation?

A

Null

131
Q

The electrical length of any antenna wire can be increased or decreased by what way?

A

Loading

132
Q

What is the basic unit from which many complex antennas are constructed?

A

Half-wave antenna

133
Q

What term is used to indicate an antenna that is very short compared with the wavelength of the operating frequency?

A

Doublet

134
Q

What is the simplest form of a practical antenna?

A

Doublet

135
Q

What type of antenna is the shortest antenna that can be used in free space?

A

1/2 wavelength

136
Q

What is an ordinary half-wave antenna that has one or more additional conductors connected across its ends?

A

Folded dipole

137
Q

What is a parasitic element referred to as when it operates to reinforce energy coming from the driver toward itself?

A

Director

138
Q

What is a parasitic element referred to as if it is placed so it causes maximum energy radiation in a direction away from itself and toward the driven element?

A

Reflector

139
Q

What designates an array in which the direction of maximum radiation is perpendicular to the plane containing these elements?

A

Broadside array

140
Q

What type of array is it when all the elements lie in a straight line with no radiation at the ends of the array?

A

Collinear

141
Q

What type of array is it when the principal direction of radiation is along the plane of the array and perpendicular to the elements?

A

End-fire

142
Q

What property of an array is the proportion of energy radiated in the principle direction of radiation to the energy radiated in the opposite direction?

A

Front-to-back ratio

143
Q

What is an antenna that is a wavelength or longer at the operating frequency?

A

Long-wire

144
Q

What is a horizontal, long-wire antenna designed especially for the reception and transmission of low-frequency, vertically polarized ground waves?

A

Beverage antenna

145
Q

What is one of the most popular fixed-station antennas because it is very useful in point-to-point communications?

A

Rhombic

146
Q

What is a half-wave radiator with a reflector?

A

Corner-Reflector antenna

147
Q

What is the heating of an insulating material by placing it in a high-frequency electric field?

A

Dielectric heating

148
Q

What parts of the human body are highly susceptible to dielectric heating?

A

Eyes

149
Q

What is the area of radiation pattern that is covered by radiation?

A

Lobe

150
Q

The optimu gain of broadside array is obtained when the elements are spaced what distance apart?

A

0.65 wavelength

IT1 SEP EXAM 2018 (10 decks)

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