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Subelement D

Display & Control Systems

Section 30

Video Amplifiers and Sweep Circuits

What are the usual input signals to the video amplifier?

  • Low level video.
  • Fixed range rings.
  • Variable range rings.
  • Correct Answer
    All of the above.

All objects displayed on-screen must have previously been amplified by the Video Amplifier, thus Answer D. is the right answer.

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Which of the following would not normally be an input to the video amplifier?

  • Fixed range rings.
  • Variable range rings.
  • Correct Answer
    Resolver signal.
  • Low level video.

A Resolver is a circuit that converts a mechanical position into an electrical signal. In a RADAR system a Resolver translates the antenna's rotational position in degrees into an electrical signal that the RADAR uses to "know" where the antenna is pointing at.

The antenn's rotational position is itself not rendered on the display screen, thus it is not an input to the video aplifier. Only elements A., B. and D. are rendered on-screen.

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The purpose of the sweep amplifier is to:

  • Increase the power of the video amplifier.
  • Correct Answer
    Drive the CRT deflection coils.
  • Drive the resolver coils.
  • All of the above.

The CRT's Deflection Coils deflect the electron beam so it sweeps the CRT's display area from left to right and top to bottom.

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How many deflection coils are driven by the sweep amplifier?

  • 4
  • 3
  • Correct Answer
    2
  • 1

The CRT's Deflection Coils deflect the electron beam so it sweeps the CRT's display area from left to right and top to bottom.

One coil deflects the beam horizontally while another coil deflects the bam vertically, so there are 2 deflection coils.

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The main purpose of the sweep generator is to provide:

  • Antenna information.
  • Range rings.
  • Composite video to the cathode of the CRT.
  • Correct Answer
    The drive signal to the sweep amplifier.

Hint: “sweep” appears in both the question and the correct answer. Generators can drive electronic devices.

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The main purpose of the video amplifier is to provide:

  • Correct Answer
    Composite video to the cathode of the CRT.
  • Resolver signals
  • Antenna X and Y signals.
  • Provide the drive signal to the sweep amplifier.

Composite video is a video signal containing information on all three colors: Red, green and blue.

The video signal is fed to the CRT - Cathode-Ray Tube's cathode by the video amplifier.

The CRT has an aluminum mesh a very short distance from the phosphor layer coating the inside of the display area that separates the electrons coming from the electron gun (cathode) so only the "red" electrons hit the red phosphor, the "green" electrons hit the green phosphor and the "blue" electrons hit the and the blue phosphor.

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