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NEETS > NEETS 18 1,2,3,4 > Flashcards

NEETS 18 1,2,3,4 Flashcards

1
Q

Q1. Radar surface-angular measurements are referenced to true north and measured in what plane?

A

A1. Horizontal plane.

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2
Q

The distance from a radar set to a target measured along the line of sight is identified by what term?

A

Range

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3
Q

Q3. What is the speed of electromagnetic energy traveling through air?

A

A3. Approximately the speed of light (162,000 nautical miles per second).

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4
Q

How much time is required for electromagnetic energy to travel 1 nautical mile and return to the source?

A

A4. 12.36 microseconds.

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5
Q

Q5. In addition to recovery time, what determines the minimum range of a radar set?

A

A5. Pulse width.

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6
Q

Atmospheric interference with the travel of electromagnetic energy increases with what rf energy characteristic?

A

Frequency

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7
Q

Q7. How is prt related to prf?

A

1/prt=prf

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8
Q

Q8. What type of radar transmitter power is measured over a period of time?

A

A8. Average power.

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9
Q

Q9. What term is used to describe the product of pulse width and pulse-repetition frequency?

A

A9. Duty cycle.

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10
Q

Q10. What type of target bearing is referenced to your ship?

A

A10. Relative bearing.

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11
Q

Q11. What type of radar detects range, bearing, and height?

A

A11. Three-dimensional.

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12
Q

Q12. What characteristic(s) of radiated energy is (are) altered to achieve electronic scanning?

A

A12. Frequency or phase.

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13
Q

What term is used to describe the ability of a radar system to distinguish between targets that are close together?

A

A13. Target resolution.

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14
Q

Q14. The degree of bearing resolution for a given radar system depends on what two factors?

A

A14. Beam width and range.

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15
Q

What happens to the speed of electromagnetic energy traveling through air as the altitude increases?

A

A15. Speed increases.

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16
Q

What term is used to describe a situation in which atmospheric temperature first increases with altitude and then begins to decrease?

A

Temperature inversion

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17
Q

What radar subsystem supplies timing signals to coordinate the operation of the complete system?

A

A17. Synchronizer.

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18
Q

When a transmitter uses a high-power oscillator to produce the output pulse, what switches the oscillator on and off?

A

A18. High-voltage pulse from the modulator.

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19
Q

Q19. What radar component permits the use of a single antenna for both transmitting and receiving?

A

Duplexer

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20
Q

Q20. What is the simplest type of scanning?

A

A20. Single lobe.

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21
Q

How does the operator of a single-lobe scanning system determine when the target moves off the lobe axis?

A

A21. The reflected signals decrease in strength.

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22
Q

Q22. What are the two basic methods of scanning?

A

A22. Mechanical and electronic.

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23
Q

Q23. Rotation of an rf-feed source to produce a conical scan pattern is identified by what term?

A

A23. Nutation.

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24
Q

Q24. The Doppler effect causes a change in what aspect of rf energy that strikes a moving object?

A

A24. Frequency.

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25
Q

Q25. The Doppler variation is directly proportional to what radar contact characteristic?

A

Velocity

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26
Q

Q26. The Doppler method of object detection is best for what type objects?

A

A26. Fast-moving targets.

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27
Q

Q27. The beat frequency in a swept-frequency transmitter provides what contact information?

A

Range

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28
Q

What factor determines the difference between the transmitted frequency and the received frequency in an fm transmitter?

A

A28. Travel time.

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29
Q

Q29. What type of objects are most easily detected by an fm system?

A

A29. Stationary.

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30
Q

Q30. What transmission method does NOT depend on relative frequency or target motion?

A

A30. Pulse modulation.

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31
Q

What transmission method uses a stable cw reference oscillator, which is locked in phase with the transmitter frequency?

A

A31. Pulse-Doppler.

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32
Q

Q32. What type of radar provides continuous range, bearing, and elevation data on an object?

A

A32. Track radar.

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33
Q

Q33. Radar altimeters use what type of transmission signal?

A

A33. Frequency modulated (fm).

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34
Q

Q34. A surface-search radar normally scans how many degrees of azimuth?

A

A34. 360 degrees.

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35
Q

Q35. What limits the maximum range of a surface-search radar?

A

A35. Radar horizon.

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36
Q

Q36. What is the shape of the beam of a surface-search radar?

A

A36. Wide vertically, narrow horizontally.

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37
Q

Q37. Air-search radar is divided into what two basic categories?

A

A37. 2D and 3D.

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38
Q

Q38. What position data are supplied by 2D search radar?

A

A38. Range and bearing.

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39
Q

Why do 2D air-search radars use relatively low carrier frequencies and low pulse-repetition rates?

A

A39. Increased maximum range.

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40
Q

Q40. Why is the range capability of 3D radar usually less than the range of 2D radar?

A

A40. Higher operating frequency.

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41
Q

Q41. Fire-control tracking radar most often radiates what type of beam?

A

A41. A narrow circular beam.

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42
Q

Q42. Tracking radar searches a small volume of space during which phase of operation?

A

Acquisition

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43
Q

Q43. What width is the pulse radiated by fire-control tracking radar?

A

A43. Very narrow.

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44
Q

Q44. Which beam of missile-guidance radar is very wide?

A

A44. Capture beam.

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45
Q

Q1. What is the purpose of the synchronizer in a radar system?

A

A1. Controls system operation and timing.

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46
Q

Q2. What is the purpose of the majority of circuits in a radar system?

A

A2. Timing and control.

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47
Q

Q3. A self-synchronized radar system obtains timing trigger pulses from what source?

A

Transmitter

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48
Q

Q4. What type of multivibrator can be used as a radar master oscillator?

A

A4. Free-running.

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49
Q

Q5. In an externally synchronized radar, what determines the prr of the transmitter?

A

A5. The master oscillator.

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50
Q

Q6. In figure 2-1, what causes the initial and final pulses on the receiver output signal?

A

A6. Leakage from the duplexer.

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51
Q

Q7. What basic circuits meet the requirements of an externally synchronized master oscillator?

A

A7. Sine-wave oscillator, single-swing blocking oscillator, and master-trigger (astable) multivibrator.

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52
Q

Q8. Name a disadvantage of sine-wave oscillator synchronizers.

A

A8. It requires additional shaping circuits.

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53
Q

Q9. Which of the basic timing circuits produces sharp trigger pulses directly?

A

A9. Blocking oscillators.

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54
Q

Q10. What are the two basic types of transmitters?

A

A10. Keyed oscillator and power-amplifier chain.

55
Q

Q11. What controls transmitter pulse width?

A

A11. The modulator.

56
Q

Q12. In addition to a flat top, what characteristics must a modulator pulse have?

A

A12. Steep leading and trailing edges.

57
Q

Q13. What type of modulator is most commonly used in modern radar systems?

A

A13. Line-pulsed.

58
Q

Q14. What three types of storage elements most often are used in modulators?

A

A14. Capacitor, artificial transmission line, or pulse-forming network.

59
Q

What characteristic is determined by the time required for a voltage wave to travel from the input end of an artificial transmission line to the output end and back again?

A

A15. Pulse width.

60
Q

Q16. What type of tube best meets the requirements of a modulator switching element?

A

Thyratron

61
Q

Q17. What modulator element controls the rate at which the storage element charges?

A

A17. The charging impedance.

62
Q

Q18. What is the frequency range of magnetron oscillators?

A

A18. 600-30,000 megahertz.

63
Q

Q19. What two forms of instability are common in magnetrons?

A

A19. Mode skipping and mode shifting.

64
Q

Q20. What is the effect on magnetron operation if the magnetic field strength is too high?

A

A20. The magnetron will not oscillate.

65
Q

Q21. What is the typical frequency range about the center frequency of a tunable magnetron?

A

A21. 5 percent.

66
Q

What is the primary advantage of power-amplifier transmitters over keyed-oscillator transmitters?

A

A22. Frequency stability.

67
Q

In the power amplifier shown in figure 2-10, what two signals are mixed to produce the output signal?

A

A23. Local oscillator and coherent oscillator.

68
Q

Q24. What type of klystron is used as the final stage of a power-amplifier transmitter?

A

A24. Multicavity klystron.

69
Q

What transmitter component allows the radiation of a large number of discrete frequencies over a wide band?

A

A25. Frequency synthesizer.

70
Q

Q26. What is the result of pulsing a pulsed rf amplifier when no rf is present?

A

A26. Oscillations at an undesired frequency.

71
Q

Q27. What type of switches are used as duplexers?

A

A27. Electronic.

72
Q

Q28. What tube in a duplexer has the primary function of disconnecting the receiver?

A

A28. Tr tube.

73
Q

Q29. How may the tr tube ionization speed be increased?

A

A29. Apply keep-alive voltage.

74
Q

The actions of the tr and atr circuits depend on the impedance characteristics of what length of transmission line?

A

A30. Quarter-wavelength section.

75
Q

During which of the transmit or receive cycles are both the tr and atr tubes of a parallelconnected duplexer ionized (arcing)?

A

A31. Transmit.

76
Q

Q32. In a series-connected duplexer, what tube (tr or atr), if any, fires during the receive cycle?

A

A32. Neither fires.

77
Q

To propagate energy down an arm of a hybrid ring duplexer, the two fields at the junction of the arm and the ring must have what phase relationship?

A

A33. 180 degrees out of phase.

78
Q

Q34. What is the greatest limiting factor in a receiver’s detectable range?

A

A34. Noise.

79
Q

Q35. What type of receiver is most often used in radar systems?

A

A35. Superheterodyne.

80
Q

Q36. What IF frequencies are normally used in radar receivers?

A

A36. Thirty or sixty megahertz.

81
Q

Which component of the receiver produces the signal that is mixed with the received signal to produce the IF signal?

A

A37. Local oscillator.

82
Q

Q38. What receiver circuit actually produces the IF frequency?

A

A38. Mixer.

83
Q

Q39. The IF amplifiers are connected in what amplifier configuration?

A

A39. Cascade.

84
Q

Q40. Which receiver component converts the IF pulses to video pulses?

A

A40. Detector.

85
Q

Which of the two types of automatic gain control, agc or iagc, is most effective in radar use for the Navy?

A

A41. IAGC.

86
Q

Q42. Immediately after the transmitter fires, stc reduces the receiver gain to what level?

A

A42. Zero.

87
Q

Q43. How does ftc affect receiver gain, if at all?

A

A43. FTC has no effect on receiver gain.

88
Q

Q44. What type of target has a fixed phase relationship from one receiving period to the next?

A

Stationary

89
Q

What signal is used to synchronize the coherent oscillator to a fixed phase relationship with the transmitted pulse?

A

A45. Coho lock pulse.

90
Q

Q46. What is the phase relationship between the delayed and undelayed video?

A

A46. Opposite.

91
Q

When a large signal and a small signal are applied to a lin-log amplifier at the same time, what is the effect on the small signal?

A

A47. Amplification is reduced.

92
Q

Q48. What happens to the overall gain of a lin-log amplifier as each stage saturates?

A

A48. Decreases.

93
Q

Q49. A monopulse receiver has how many separate channels?

A

A49. Three.

94
Q

If a target is on the bearing axis of the radiated beam, what is the input to the bearing IF channel?

A

A50. Zero.

95
Q

What characteristic of the bearing and elevation output signals determines the direction of antenna movement?

A

A51. Phase.

96
Q

Q1. What are the three fundamental quantities involved in radar displays?

A

A1. Range, bearing, and elevation.

97
Q

Q2. What are the required radar inputs for proper indicator operation?

A

A2. Triggers, video, and antenna information.

98
Q

Q3. What coordinates are displayed on an rhi scope?

A

A3. Range and elevation.

99
Q

Q4. What coordinates are presented on a ppi scope?

A

A4. Range and bearing.

100
Q

Q5. What type of deflection is preferred for a crt electron beam?

A

A5. Electromagnetic.

101
Q

Q6. Which of the two types of deflection coils (fixed or rotating) is used most often?

A

Fixed

102
Q

What type of ranging circuit is most often used with a radar that requires extremely accurate range data?

A

A7. Range gate or range step.

103
Q

Q8. The range sweep in a range-gate generator is started at the same time as what other pulse?

A

A8. Transmitter.

104
Q

Q9. Range-marker generators produce pulses based on what radar constant?

A

A9. The radar mile (12.36 microseconds).

105
Q

Q10. What radar scope uses a range step for range measurement?

A

A10. The A scope.

106
Q

Q11. Which of the two general classes of antennas is most often used with radar?

A

A11. Directional.

107
Q

Q12. The power gain of an antenna is directly related to what other antenna property?

A

A12. Directivity.

108
Q

Q13. A parabolic reflector changes a spherical wavefront to what type of wavefront?

A

A13. Plane.

109
Q

Q14. How many major lobes are produced by a paraboloid reflector?

A

One

110
Q

Q15. What type of radiator normally drives a corner reflector?

A

A15. Half-wave.

111
Q

Q16. The broadside array consists of a flat reflector and what other elements?

A

A16. Two or more half-wave dipoles.

112
Q

Q17. Horn radiators serve what purpose other than being directional radiators?

A

A17. Waveguide impedance matching devices.

113
Q

Q1. The spectrum of a radar transmitter describes what characteristic of the output pulse?

A

A1. Frequency distribution.

114
Q

Q2. Where should the transmitter spectrum be located with respect to the receiver response curve?

A

A2. In the center.

115
Q

Q3. The ideal radar spectrum has what relationship to the carrier frequency?

A

A3. Symmetrical above and below the carrier frequency.

116
Q

The display screen of a spectrum analyzer presents a graphic plot of what two signal characteristics?

A

A4. Power and frequency.

117
Q

Q5. The peak power of a radar depends on the interrelationship of what other factors?

A

A5. Average power, pulse width, and prt.

118
Q

Q6. Transmitter power readings are most often referenced to what power level?

A

A6. 1 milliwatt.

119
Q

Q7. A loss of receiver sensitivity has the same effect on range performance as what other loss?

A

A7. Transmitter power loss.

120
Q

Q8. You determine receiver sensitivity by measuring the power level of what signal?

A

A8. Minimum discernible signal (mds).

121
Q

Q9. When measuring receiver sensitivity, what quantities must you add to the dBm reading obtained on the signal generator or test set?

A

A9. Attenuations of the directional coupler and the connecting cable.

122
Q

Q10. Receiver bandwidth is defined as those frequencies spread between what two points of the receiver response curve?

A

A10. Half-power points.

123
Q

Q11. The end of the usefulness of a tr tube is indicated by an increase in what quantity?

A

A11. Recovery time.

124
Q

Q12. Most shipboard distribution systems use ac power that has what number of phases?

A

Three

125
Q

Q13. How is emergency power applied when normal power is lost?

A

Automatically

126
Q

What device is used to switch power from the normal source to an alternate source for nonvital users?

A

A14. Manual bus transfer (MBT) unit.

127
Q

Q15. What procedure should you use when a power input to your equipment is missing?

A

A15. Work backwards from the load to the source.

128
Q

Q16. What is the normal source of dry air for a radar system?

A

A16. Ship’s central dry-air system.

129
Q

What is the major difference between the electronics dry-air branch and the vital service lp air main?

A

A17. Degree of dehydration.

130
Q

Q18. What is the air control panel designed to control?

A

Pressure

131
Q

Q19. What type of cooling is used to control ambient room temperature?

A

A19. Air conditioning.

132
Q

Q20. A typical liquid-cooling system is composed of what loops?

A

A20. Primary and secondary.

133
Q

Q21. What loop of a cooling system is often supplied by sea water?

A

A21. The primary loop.

NEETS (11 decks)

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