Questions on radial beam power tube principles

Discussion in 'Amateur Radio Amplifiers' started by WB5HDF, Jul 1, 2021.

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  1. WB5HDF

    WB5HDF Ham Member QRZ Page

    Does a radial beam power tetrode, for example a 4-65A or 4CX1500, form a virtual cathode space charge region between screen and plate that returns secondary emission electrons to the plate at plate potentials near and less than the potential of the screen?

    What about the radial beam power pentode? If the suppressor is set to cathode potential, it should have the same influence on secondary electrons from the plate as the suppressor in a small receiving type pentode. Is there any other benefit of beams in a radial beam power pentode other than reducing screen current? Possibly reducing suppressor current if the suppressor potential is non-zero?

    I'd be grateful for referrals to texts and articles that describe radial beam power tube principles.

  2. NW2K

    NW2K Ham Member QRZ Page

    KD2ACO likes this.
  3. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    Some on-line resources to google and download:

    "Tubes 201" - How Vacuum Tubes Really Work

    Vacuum Tubes by Karl Spangenberg, Chapters 9-11.

    Vacuum Tube Design, RCA Manufacturing Company, 1940

    Theory and Applications of Vacuum Tubes, Herbert J. Reich, McGraw-Hill, 1944

    Engineering Electronics by Happell and Hasselberth, McGraw-Hill, 1953



    Attached Files:

    K0OKS likes this.
  4. SWL37632

    SWL37632 QRZ Member

    Check out the Eimac "Care and Feeding of Power Grid Tubes" book.

    The Eimac/CPII website has the PDF version for download on their website:

    20+ WPM 1970's Extra
  5. KL7AJ

    KL7AJ Ham Member QRZ Page

    The radial beam power tube has a geometry such that any secondary emission is deflected off so it no longer interferes with the main electron flow. This way, the need for a suppressor grid is eliminated.
  6. WB5HDF

    WB5HDF Ham Member QRZ Page

    Thank you all for the information!
    AC0OB, thank you for mentioning Spangenberg's Vacuum Tubes and for attaching the Jonker, Benham and Meacham papers - fantastic!

    Can Philips Technical Review be found on the WWW?

    I believe this statement to be correct: In the radial beam tube, anode secondary electrons are returned to the anode at anode potentials near or less than the screen potential due to the space charge potential minimum formed between the screen and anode.
    At low anode currents this may not obtain, but most amplifiers don't operate the tube at low anode current and voltage simultaneously.

    The cylindrical anode beam tube with coaxial cylindrical cathode and coaxial control grid formed of rods parallel to the axis of the cathode forms electron beams of rectangular cross section. A first approximation is that this is equivalent to parallel plane cathode and anode electrode arrangement: (fig. 5.8 - Geppert, Basic Electron Tubes, 1951, p. 170)

    Harry C. Thompson, 1935:


    Attached Files:

  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I have radial beam power tires on my car. On all my cars.

    Currently Michelin, but I've used other types.
  8. WB5HDF

    WB5HDF Ham Member QRZ Page

    Shuffling around in the stacks some more turned up this very informative paper:
    Winfield G. Wagener, "500-Mc Transmitting Tetrode Design Considerations", Proc. IRE, May 1948, pp. 611 - 619

    Wagener Fig. 1 (compare to H.C. Thompson Fig. 5):
    Last edited: Jul 19, 2021

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