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ET1 SEP EXAM 2018 > NAVEDTRA 14190A, NAVY ELECTRICITY AND ELECTRONICS TRAINING SERIES. MODULE 18-RADAR PRINCIPLES > Flashcards

NAVEDTRA 14190A, NAVY ELECTRICITY AND ELECTRONICS TRAINING SERIES. MODULE 18-RADAR PRINCIPLES Flashcards

1
Q

Which term is used to refer to electronic equipment that detect the presence, direction, height, and distance of objects by using reflected electromagnetic energy?

A

Radar

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2
Q

What is used by radar sets to determine the direction and distance of the reflecting object?

A

Echo

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3
Q

The surface of the earth is represented by an imaginary flat plane, tangent (or parallel) to the earth’s surface at that location. What is this plane referred to as?

A

Horizontal plane

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4
Q

What is the line from the radar set directly to the object referred to as?

A

Line of Sight (LoS)

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5
Q

What is the angle called between the horizontal plane and the los?

A

Elevation angle

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6
Q

Approximately how many statute miles per second does electromagnetic energy travel through the air?

A

186,000

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7
Q

Approximately how many nautical miles are equal to 186,000 statute miles?

A

162,000

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8
Q

Approximately how many feet are there per nautical mile?

A

6,080

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9
Q

What is radar timing usually expressed in?

A

Microseconds

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10
Q

Approximately how many feet per microsecond does radiated energy from a radar set travel at?

A

984

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11
Q

The range in nautical miles to an object can be found by measuring the elapsed time during a round trip of a radar pulse and dividing this quantity by what number?

A

12.36

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12
Q

Which pulse property determines the maximum range that the pulse can travel to a target and still return a usable echo?

A

Peak power

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13
Q

What is the smallest signal called that is detectable by a receiver system that can be processed and presented on an indicator?

A

Usable Echo

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14
Q

What is the frequency of the rf energy in the pulse radiated by a radar referred to as?

A

Carrier frequency

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15
Q

Radio frequency energy above what frequency is rapidly attenuated by the atmosphere?

A

3,000 megahertz

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16
Q

What is used to calculate both the peak power and average power of a radar system?

A

Duty cycle

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17
Q

Which radar target property is the angle between true north and a line pointed directly at the target?

A

True bearing

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18
Q

Which radar systems are designed to determine only the range and bearing of an object?

A

2D

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19
Q

Which type of search radar system detects altitude as well as range and bearing?

A

3D

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20
Q

Which radar property is defined as its ability to distinguish between targets that are very close together in either range or bearing?

A

Target resolution

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21
Q

Which two categories is resolution usually divided into?

A

Range and bearing

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22
Q

What is the ability referred to as of a radar system to distinguish between two or more targets on the same bearing but at different ranges?

A

Range resolution

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23
Q

What is the ability of a radar system to separate objects at the same range but at different bearings?

A

Azimuth resolution

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24
Q

What is a measure of the ability of a radar system to determine the correct range, bearing, and, in some cases, height of an object?

A

Radar accuracy

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25
Q

What is the bending of electromagnetic waves caused by a change in the density of the medium through which the waves are passing?

A

Refraction

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26
Q

What ensures that all circuits connected with the radar system operate in a definite timed relationship?

A

Synchronizer

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27
Q

What is essentially an electronic switch that permits a radar system to use a single antenna to both transmit and receive?

A

Duplexer

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28
Q

What is the systematic movement of a radar beam in a definite pattern while searching for or tracking a target?

A

Scanning

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29
Q

Which type of scanning is unsuitable for use as a tracking radar?

A

Single-lobe

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30
Q

What are the two basic methods of beam scanning?

A

Mechanical and Electronic

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31
Q

Which type of scanning is used in fire-control tracking radars?

A

Monopulse

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32
Q

What can occur as the target maneuvers or moves and the radar pulses bounce off different areas of the target and causes random reflectivity and may lead to tracking errors?

A

Scintillation

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33
Q

When radio-frequency energy transmitted from a fixed point continuously strikes an object that is either moving toward or away from the source of the energy, the frequency of the reflected energy is changed. What is this shift in frequency known as?

A

Doppler effect

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34
Q

What is a requirement for any Doppler radar to function?

A

Coherence

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35
Q

What is the heart of a missile guidance system?

A

Radar system

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36
Q

Which type of radar is designed to continuously scan a volume of space to provide initial detection of all targets?

A

Search

37
Q

Which type of radar provides continuous range, bearing, and elevation data on one or more targets?

A

Track

38
Q

Which type of radar systems detect and process only moving targets?

A

Moving Target Indicators

39
Q

What is the maximum range ability of surface-search radar primarily limited by radar horizon?

A

Radar horizon

40
Q

Which type of radar is used to detect the presence of surface craft and low flying aircraft and to determine their presence?

A

Surface-search

41
Q

The maximum range of air-search radar can exceed how many miles?

A

300

42
Q

Which type of radar computes accurate ranges, bearings, and altitudes of aircraft targets detected by air search radars?

A

Height-finding

43
Q

Which type of radar system provides the information used to guide a missile to a hostile target called?

A

Guidance

44
Q

What is often referred to as the “heart” of the radar system because it controls and provides timing for the operation of the entire system?

A

Synchronizer

45
Q

What is the function of the majority of circuits in radar?

A

Timing or control

46
Q

Which types of waves will be generated by the multivibrator if it is symmetrical?

A

Square

47
Q

What produces the short duration high-power rf pulses of energy that are radiated into space by the antenna?

A

Transmitter

48
Q

What controls the radar pulse width by means of rectangular dc pulse of the required duration and amplitude?

A

Modulator

49
Q

Magnetron oscillators are capable of generating rf pulses with very high peak power at frequencies ranging from 600 to how many megahertz?

A

30,000

50
Q

Which type of modulator has lower efficiency, its circuits are more complex, a higher power supply voltage is required, and it is more sensitive to voltage changes?

A

Hard-tube

51
Q

Pulse-forming networks are often insulated by immersing each circuit element in what?

A

Oil

52
Q

Typical dc power supplies for radar modulators use a half-wave rectifier, a full-wave rectifier, or which other type of rectifier?

A

Bridge

53
Q

What does the keyed-oscillator transmitter most often use as the power oscillator?

A

Magnetron

54
Q

What are the two main types of magnetron mode instability?

A

Mode skipping and mode shifting

55
Q

Which condition occurs when the magnetron fires randomly in an undesired, interfering mode during some pulse times, but not in others?

A

Mode skipping

56
Q

Which condition occurs when the magnetron changes from one mode to another during pulse time?

A

Mode shifting

57
Q

What are used in radar systems with a wide band of transmitted frequencies because they are stable over a wider frequency range?

A

Amplitrons

58
Q

What allows the transmitter to radiate a large number of discrete frequencies over a relatively wide band?

A

Frequency synthesizer

59
Q

Which term refers to the discharge of electricity through a gas-filled electron tube?

A

Glow discharge

60
Q

Which type of duplexers are the most common in radar systems?

A

Waveguide and hybrid-ring

61
Q

What is used as a duplexer in high-power radar systems?

A

Hybrid ring

62
Q

Which term refers to a condition of the receiver in which the voltage pulse at the receiver input is too large?

A

Blocking

63
Q

The superheterodyne receiver is almost always used in which type of radar systems?

A

Microwave

64
Q

Most radar receivers use a 30 MHz or which intermediate frequency?

A

60 MHz

65
Q

Which very stable microwave oscillator can be tuned by changing the repeller voltage?

A

Reflex klystron

66
Q

Which circuit is used by most radar systems to control the output of the local oscillator?

A

Automatic Frequency Control (AFC)

67
Q

Which part of a microwave receiver serves to convert the IF pulses into video pulses?

A

Detector

68
Q

What is the simplest form of detector and the most commonly used in microwave receivers?

A

Diode detector

69
Q

What is fundamentally an RC coupled amplifier that uses high-gain transistors or pentodes?

A

Video amplifier

70
Q

What is not used as frequently as other types of gain control because of the widely varying amplitudes of radar return signals?

A

AGC

71
Q

What is the appearance on a radar indicator of confusing, unwanted echos which interfere with the clear display of desired echos?

A

Clutter

72
Q

Which type of non-saturating amplifier does not ordinarily use any special gain-control circuits?

A

Lin-log amplifier

73
Q

Radar energy is distributed more or less symmetrically over a band of frequencies. What is this frequency distribution of energy known as?

A

Frequency spectrum

74
Q

What presents a graphic display of energy versus frequency?

A

Spectrum analyzer

75
Q

What does the distribution of power over the radar frequency spectrum depend on?

A

Modulation

76
Q

The electronic frequency counter, wave meter, along with what else are the devices used to determine the basic carrier frequency of a radar transmitter?

A

Echo box?

77
Q

What is defined as the weakest signal that produces a visable receiver output (on a scope?)

A

MDS

78
Q

A typical receiver sensitivity reading on a modern radar should be in the vicinity of what?

A

-105 dBm

79
Q

What is defined as the frequency spread between the half-power points on the receiver response curve?

A

Receiver bandwidth

80
Q

In various radars, the recovery time may differ from less than 1 microsecond to about how many microseconds?

A

20

81
Q

When present on transmission lines and waveguides what indicate an impedance mismatch between a transmitter or receiver and its antenna?

A

Standing waves

82
Q

A high vswr (what or higher) indicates that the characteristic impedance of a transmission line differs greatly from the terminating impedance?

A

1.5 to 1

83
Q

Most ac power distribution systems in naval vessels are how many-volt, 60-hertz, 3-phase, 3-wire, ungrounded systems?

A

440

84
Q

Which type of equipment is used to provide power to vital loads?

A

Automatic Bus Transfer (ABT)

85
Q

What do microwave components require, such as waveguides, cavities, and power amplifiers, to prevent arcing and internal corrosion?

A

Dry air

86
Q

What is one of the best mediums for cooling high-power components, and, in many cases, the only medium that may be used?

A

Distilled water

87
Q

Radar peak power may reach how many watts or more?

A

One million

88
Q

Klystrons, magnetrons, rectifiers, or other tubes that employ an excitation of how many volts or more may emit X rays out to a few feet?

A

15,000

ET1 SEP EXAM 2018 (28 decks)

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