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ITC EXAM 2019 > 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

(73 cards)

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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 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 3000KHz

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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

30-300 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

Wave length

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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 a 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

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23
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

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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

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25
The Ionosphere extends upward from about 31.1 miles to a height of about how many miles?
250
26
What is the most important region of the atmosphere for long distance point-to-point communications?
Ionosphere
27
What are the two principal ways in which electromagnetic (radio) energy travels from a transmitting antenna to a receiving antenna?
Ground and Sky waves
28
The surface wave is impractical for long distance transmissions at frequencies above what frequency?
2 megahertz
29
Which frequency band is used for sky wave propagation?
High Frequency (HF)
30
What is the process known as of upsetting electrical neutrality?
Ionization
31
What occurs when the free electrons and positive ions collide with each other?
Recombination
32
How many layers is the Ionosphere composed of?
Three
33
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?
Critical frequency
34
What is the distance from the transmitter to the point where the sky wave is first returned to Earth?
Skip distance
35
What results in the loss of energy of a radio wave and has a pronounced effect both on the strength of received signals and the ability to communicate over long distances?
Absorption
36
Fading on ionospheric circuits is mainly a result of what?
Multipath propagation
37
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?
Frequency diversity
38
When a wide band of frequencies is transmitted simultaneously, each frequency will vary in the amount of fading. What is this variation called?
Selective fading
39
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?
Free space loss
40
There is little natural interference above what frequency?
30 megahertz
41
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?
Skip zone
42
How many main classes can the regular variations that affect the extent of ionization in the ionosphere be divided into?
Four
43
What are responsible for variations in the ionization level of the ionosphere?
Sunspots
44
Long distance propagation of hf radio waves is almost totally "blanked out" when what occurs?
Sudden Ionospheric Disturbance (SID)
45
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?
Four
46
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 the frequency known as?
Maximum Usable Frequency (MUF)
47
Raindrops cause greater attenuation by scattering than by absorption at frequencies above what?
100 megahertz
48
Fog can cause serious attenuation by absorption at frequencies above what?
2 gigahertz
49
What is the condition when layers of warm air are formed above layers of cool air known as?
Temperature inversion
50
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?
7
51
What region does virtually all weather phenomena occur in?
Troposphere
52
Radio waves of frequencies below what normally have wavelengths longer than the size of weather turbulences?
30 megahertz
53
The usable frequency range for tropospheric scattering is from about 100 megahertz to what?
10 gigahertz
54
A correctly designed tropospheric scattering is from about 100 megahertz to what?
10 gigahertz
55
A correctly designed tropospheric scatter circuit will provide highly reliable service for distances ranging from 50 miles to how many miles?
500
56
Which device is designed to guide electrical energy from one point to another?
Transmission line
57
Which type of line consists of two insulated wires twisted together to form a flexible line without the use of spacers?
Twisted pair
58
Leakage caused by the condensation of moisture is prevented in some rigid line applications by the use of what?
Inert gas
59
What was developed to replace rubber and eliminate high-frequency losses associated with rubber insulators?
Polyethylene plastic
60
The radius of bends in the wavelength must measure greater than how many wavelengths at the operating frequency of the equipment to avoid excessive attenuation?
Two
61
Line losses may be any of three types-Radiation/induction, Dielectric, and what else?
Copper
62
Copper losses can be minimized and conductivity increased in an RF line by plating the line with what?
Silver
63
Which type of losses occur because some magnetic lines of force about a conductor do not return to the conductor when the cycle alternates?
Radiation
64
What determines the amount of current that can flow when a given voltage is applied to an infinitely long line?
Characteristic impedance
65
The characteristic impedance of lines in actual use normally lies between 50 and how many ohms?
600
66
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?
Load impedance
67
If a line is not terminated in characteristic impedance, what is it said to be?
Finite
68
What are voltages called that are moving toward the receiving end of a line?
Incident voltages
69
Which type of line has no standing waves of current and voltage?
Nonresonant
70
Which type of line has a finite length and is not terminated in its characteristic impedance?
Resonant
71
What is the maximum voltage to minimum voltage on a line called?
VSWR
72
What are hollow metal tubes used to transfer energy from one point to another?
Waveguides
73
What are theoretical properties (inductance, resistance, and capacitance) of a transmission line that are lumped into a single component?
Lumped constants

ITC EXAM 2019 (18 decks)

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