Neets Module 6 Assignment 2

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CVN68
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165451
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Neets Module 6 Assignment 2
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2012-08-09 16:27:05
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Neets
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  1. What is the major difference in grid construction between power pentodes and conventional pentodes?
    Conventional pentodes have a staggered grid arrangement, while power pentodes have a shielded grid arrangement.
  2. Beam-forming tubes and power tubes are similar except that power pentodes lack what element?
    Beam-forming plates.
  3. What effect does the shielding of the screen grid by the control grid have on plate current in beam-forming tetrodes?
    By increasing the number of electrons that reach the plate, plate current is increased.
  4. What effect does a large negative input signal applied to a variable-mu tube have on (a.) conduction through the control grid, and (b.) gain of the tube?
    A large negative voltage causes conduction to occur only at the center of the grid
  5. Identify the type of electron tube(s) that would be most suitable for the following applications. (a.) Power amplifier (b.) Voltage amplifier with small signal inputs (c.) Low distortion amplifiers for use with large signal inputs
    • Decreases gain.
    • (a.) Power pentode or beam-forming tetrode.
    • (b.) Conventional tube.
    • (c.) Variable-mu tube.
  6. What effect does transit time have on a conventional triode operated at uhf frequencies?
    It causes the control grid to short to the cathode.
  7. How do uhf tubes counter the effects of transit time?
    By reducing the spacing between tube elements.
  8. Why can acorn and doorknob tubes NOT handle large amounts of power?
    The close spacing of tube elements allows for the ready formation of arcs or short circuits.
  9. What type of uhf tube was developed to handle large amounts of power?
    Planar
  10. What are two advantages that gas-filled tubes have over conventional electron tubes?
    • They can carry more current.
    • They maintain a constant IR drop across the tube.
  11. Once ionization has occurred in a thyratron, what control does the control grid have over the tube's operation?
    None.
  12. What precautions should be exercised when using mercury-vapor thyratrons?
    The filament's voltage should be applied to the tube at least 30 seconds before attempting to operate the tube.
  13. Cold-cathode tubes can be used as voltage regulators because of what characteristic?
    They have the ability to maintain a constant voltage drop across the tube despite changes in current flow.
  14. What is the unique ability of the CRT?
    To visually display electronic signals.
  15. What are the three main parts of CRT?
    • Electron gun.
    • Deflection system
    • Screen.
  16. What term is used for the ability of a spot on a CRT screen to continue to glow after the electron bean has struck it and moved away?
    Persistence.
  17. The electron beam in a CRT is made to sweep from left to right across the screen. What tube element causes this sweeping motion?
    The horizontal-deflection plate.
  18. In applications where electronic waveforms are displayed on a CRT screen, the input signal is normally applied to what CRT element?
    The vertical-deflection plate.

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