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

Question 1

Which term means “movement through a medium”?

Answer 1

Propagation

Question 2

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

Answer 2

Wave

Question 3

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

Answer 3

Wave motion

Question 4

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?

Answer 4

Transverse

Question 5

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

Answer 5

Longitudinal

Question 6

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

Answer 6

Medium

Question 7

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

Answer 7

Reference line

Question 8

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

Answer 8

Wavelength

Question 9

Which unit of measurement are wavelengths expressed in?

Answer 9

Meters

Question 10

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

Answer 10

Amplitude

Question 11

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

Answer 11

Wave train

Question 12

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

Answer 12

Hertz

Question 13

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

Answer 13

Hertz

Question 14

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?

Answer 14

Velocity

Question 15

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

Answer 15

Period

Question 16

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

Answer 16

Incident

Question 17

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

Answer 17

Angle of reflection

Question 18

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

Answer 18

Law of reflection

Question 19

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

Answer 19

Diffraction

Question 20

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?

Answer 20

Doppler Effect

Question 21

How does sound travel through a medium?

Answer 21

Wave motion

Question 22

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

Answer 22

Sound

Question 23

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

Answer 23

15 hertz

Question 24

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

Answer 24

Ultrasonic

Question 25

What are sounds below 15 hertz known as?

Answer 25

Infrasonic

Question 26

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

Answer 26

Three

Question 27

Which two general groups may sounds be broadly classified into?

Answer 27

Noise or Tones

Question 28

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

Answer 28

Quality

Question 29

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

Answer 29

Pitch

Question 30

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

Answer 30

Intensity

Question 31

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

Answer 31

Loudness

Question 32

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

Answer 32

Elasticity and Density

Question 33

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

Answer 33

Elasticity

Question 34

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

Answer 34

Density

Question 35

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

Answer 35

1,087

Question 36

What is the science of sound referred to as?

Answer 36

Acoustics

Question 37

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

Answer 37

Echo

Question 38

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

Answer 38

Reverberation

Question 39

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

Answer 39

Interference

Question 40

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

Answer 40

Noise

Question 41

What is light a form of?

Answer 41

Electromagnetic radiation

Question 42

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

Answer 42

Photons

Question 43

Approximately how many miles per second does light travel?

Answer 43

186,000

Question 44

What is a large volume of light called?

Answer 44

Beam

Question 45

What is a narrow volume of light called?

Answer 45

Pencil

Question 46

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

Answer 46

Transparent

Question 47

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

Answer 47

Transparent

Question 48

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

Answer 48

Translucent

Question 49

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

Answer 49

1675

Question 50

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

Answer 50

7.5

Question 51

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

Answer 51

Spectrum

Question 52

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

Answer 52

Antenna

Question 53

Which two primary components does an electromagnetic wave consist of?

Answer 53

Electric and Magnetic field

Question 54

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

Answer 54

Photon

Question 55

Which units are used for measuring the wavelength of light?

Answer 55

Angstrom

Question 56

What are the primary colors of light?

Answer 56

Red, Green, and Blue

Question 57

What are the complementary colors of light?

Answer 57

Magenta, yellow, and cyan

Question 58

Which two basic fields are associated with every antenna?

Answer 58

Induction and Radiation

Question 59

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

Answer 59

Induction

Question 60

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

Answer 60

Half-wave

Question 61

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

Answer 61

Radio wave

Question 62

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

Answer 62

Sine wave

Question 63

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

Answer 63

Frequency

Question 64

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

Answer 64

300 GHz

Question 65

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

Answer 65

100 gigahertz

Question 66

What is the VLF frequency range?

Answer 66

3 to 30 KHz

Question 67

What is the LF frequency range?

Answer 67

30 to 300 KHz

Question 68

What is the MF frequency range?

Answer 68

300 to 3000 KHz

Question 69

What is the HF frequency range?

Answer 69

3 to 30 MHz

Question 70

What is the VHF frequency range?

Answer 70

30 to 300 MHz

Question 71

What is the UHF frequency range?

Answer 71

300 to 3000 MHz

Question 72

What is the SHF frequency range?

Answer 72

3 to 30 GHz

Question 73

What is the EHF frequency range?

Answer 73

30 to 300 GHz

Question 74

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

Answer 74

Harmonic

Question 75

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

Answer 75

Period

Question 76

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

Answer 76

Wavelength

Question 77

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?

Answer 77

186,000

Question 78

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

Answer 78

Plane of polarization

Question 79

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

Answer 79

Ionosphere

Question 80

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 South Pole and how many miles at the equator?

Answer 80

11.2

Question 81

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

Answer 81

Stratosphere

Question 82

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

Answer 82

250

Question 83

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

Answer 83

Ionosphere

Question 84

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

Answer 84

Ground and Sky waves

Question 85

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

Answer 85

2 megahertz

Question 86

Which frequency band is used for sky wave propagation?

Answer 86

High Frequency (HF)

Question 87

What is the process known as of upsetting electrical neutrality?

Answer 87

Ionization

Question 88

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

Answer 88

Recombination

Question 89

How many layers is the ionosphere composed of?

Answer 89

Three

Question 90

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

Answer 90

Critical frequency

Question 91

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

Answer 91

Skip distance

Question 92

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?

Answer 92

Skip Zone

Question 93

What results in a 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?

Answer 93

Absorption

Question 94

Fading on ionospheric circuits is mainly a result of what?

Answer 94

Multipath propagation

Question 95

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

Answer 95

Frequency diversity

Question 96

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

Answer 96

Selective fading

Question 97

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?

Answer 97

Free space loss

Question 98

There is little natural interference above what frequency?

Answer 98

30 megahertz

Question 99

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

Answer 99

Four

Question 100

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

Answer 100

Sunspots

Question 101

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

Answer 101

Sudden Ionospheric Disturbance (SID)

Question 102

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?

Answer 102

Four

Question 103

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?

Answer 103

Maximum Usable Frequency (MUF)

Question 104

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

Answer 104

100 megahertz

Question 105

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

Answer 105

2 gigahertz

Question 106

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

Answer 106

Temperature inversion

Question 107

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

Answer 107

7

Question 108

What region does virtually all weather phenomena occur in?

Answer 108

Troposphere

Question 109

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

Answer 109

30 megahertz

Question 110

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

Answer 110

10 gigahertz

Question 111

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

Answer 111

500

Question 112

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

Answer 112

Transmission line

Question 113

Which type of line is most often used for power lines, rural telephone lines, and telegraph lines?

Answer 113

Two-wire open line

Question 114

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

Answer 114

Twisted pair

Question 115

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

Answer 115

Inert gas

Question 116

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

Answer 116

Polyethylene plastic

Question 117

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

Answer 117

Two

Question 118

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

Answer 118

Copper

Question 119

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

Answer 119

Silver

Question 120

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

Answer 120

Radiation

Question 121

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

Answer 121

Characteristic impedance

Question 122

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

Answer 122

600

Question 123

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?

Answer 123

Load impedance

Question 124

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

Answer 124

Finite

Question 125

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

Answer 125

Incident voltages

Question 126

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

Answer 126

Nonresonant

Question 127

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

Answer 127

Resonant

Question 128

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

Answer 128

VSWR

Question 129

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

Answer 129

Waveguides

Question 130

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

Answer 130

Lumped constants

Question 131

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

Answer 131

Hertz and Marconi

Question 132

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

Answer 132

Marconi

Question 133

Hertz antennas are generally used for frequencies above what?

Answer 133

2 megahertz

Question 134

Which three parts does a complete antenna system consist of?

Answer 134

Coupling device, feeder, and antenna

Question 135

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

Answer 135

Antenna

Question 136

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

Answer 136

Reciprocity

Question 137

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

Answer 137

Horizontal polarization

Question 138

Which frequencies is sky-wave transmission used?

Answer 138

High

Question 139

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?

Answer 139

100

Question 140

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

Answer 140

91

Question 141

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

Answer 141

100 megahertz

Question 142

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

Answer 142

Horizontal

Question 143

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

Answer 143

Radiated energy

Question 144

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

Answer 144

73

Question 145

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

Answer 145

65

Question 146

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

Answer 146

Radiation pattern

Question 147

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

Answer 147

Isotropic radiation

Question 148

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

Answer 148

Anisotropic

Question 149

What is used to indicate directions of minimum radiation?

Answer 149

Null

Question 150

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

Answer 150

Loading

Question 151

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

Answer 151

Half-wave antenna

Question 152

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

Answer 152

Doublet

Question 153

What is the simplest form of a practical antenna?

Answer 153

Doublet

Question 154

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

Answer 154

1/2 wavelength

Question 155

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

Answer 155

Folded dipole

Question 156

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

Answer 156

Director

Question 157

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

Answer 157

Reflector

Question 158

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

Answer 158

Broadside array

Question 159

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

Answer 159

Collinear

Question 160

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

Answer 160

End-fire

Question 161

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

Answer 161

Front-To-Back Ratio

Question 162

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

Answer 162

Long-wire

Question 163

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

Answer 163

Beverage antenna

Question 164

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

Answer 164

Rhombic

Question 165

What is a half-wave radiator with a reflector?

Answer 165

Corner-Reflector antenna

Question 166

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

Answer 166

Dielectric heating

Question 167

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

Answer 167

Eyes

Question 168

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

Answer 168

Lobe

Question 169

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

Answer 169

0.65 wavelength