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Subel. D
6 questions
Subelement D

Display & Control Systems

Section 33

Variable Range Markers

The variable range marker signal is normally fed to the input of the:

  • Sweep amplifier.
  • Low voltage power supply regulator.
  • Correct Answer
    Video amplifier.
  • Range ring oscillator.

Everything you want displayed on-screen has to go through the video amplifier or it won't get displayed, thus Answer C. is the right answer.

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The purpose of the variable range marker is to:

  • Correct Answer
    Provide an accurate means of determining the range of a moving target.
  • Provide a bearing line between own ship and a moving target.
  • Indicate the distance between two different targets.
  • Provide a means of calibrating the fixed range rings.

A VRM - Variable Range Marker allows the RADAR operator to vary the range of the Variable Range Market to place it over the desired target and read-off the distance on the RADAR display.

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How is the variable range marker usually adjusted for accuracy?

  • Adjusting the frequency of the VRM oscillator at the maximum range.
  • Adjusting the frequency of the VRM oscillator at the minimum range.
  • Adjusting the readout to match at the median range ring.
  • Correct Answer
    The minimum and maximum ranges are aligned with the matching fixed range ring.
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The panel control for the variable range marker is normally a:

  • Correct Answer
    Variable resistor.
  • Variable inductance.
  • Variable capacitance.
  • Variable resolver.

Variable resistors, a.k.a. potentiometers, are the most-used means for an operator to control an electrical circuit, thus Answer A. is the right answer.

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An important component of the VRM system is the:

  • Resolver.
  • Interference rejection circuit.
  • STC sensitivity control.
  • Correct Answer
    Shift register.

The VRM - Variable Range Marker measures distance to an object. A shift register is required as part of the electrical circuit measuring the distance on the display, thus Answer D. is the right answer.

Answer A. is wrong because the Resolver generates a signal with the heading the RADAR antenna is pointing at relative to the ship and is thus unrelated to the question being asked.

Answer B. is wrong because because interference rejection is unrelated to the question being asked.

Answer C is wrong because STC - Sensitivity Time Control is unrelated to the question being asked.

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Which of the following statements about the Variable Range Marker system is correct?

  • The VRM is an auxiliary output of the fixed range marker oscillator.
  • Correct Answer
    The VRM system develops a single adjustable range ring.
  • The VRM system is calibrated using a frequency counter.
  • The VRM system is controlled by a crystal oscillator.

Answer B. clearly states the function of the VRM so it's the right answer.

The VRM relies on its own oscillator so Answers A. and D. can't be right.

The VRM is calibrated by moving it to the nearest and to the farthest range markers without any need for a frequency counter, so Answer C. can't be right.

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