MOD 18 1,2,3 Flashcards Preview

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Flashcards in MOD 18 1,2,3 Deck (113)
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Q1. Radar surface-angular measurements are referenced to true north and measured in what plane?

A1. Horizontal plane.

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

Range

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

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

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

A4. 12.36 microseconds.

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

A5. Pulse width.

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

Frequency

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Q7. How is prt related to prf?

1/prt=prf

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

A8. Average power.

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

A9. Duty cycle.

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

A10. Relative bearing.

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

A11. Three-dimensional.

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

A12. Frequency or phase.

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

A13. Target resolution.

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

A14. Beam width and range.

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

A15. Speed increases.

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

Temperature inversion

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

A17. Synchronizer.

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

A18. High-voltage pulse from the modulator.

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

Duplexer

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Q20. What is the simplest type of scanning?

A20. Single lobe.

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

A21. The reflected signals decrease in strength.

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Q22. What are the two basic methods of scanning?

A22. Mechanical and electronic.

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

A23. Nutation.

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

A24. Frequency.

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

Velocity

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

A26. Fast-moving targets.

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

Range

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

A28. Travel time.

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

A29. Stationary.