Formulas for the Amplification Constant for Three-Element Tubes in which the Diameter of Grid Wires is Large Compared to the Spacing

Abstract

Previous formulas which have been developed for the amplification constant in plane parallel three element tubes, do not take full account of the diameter of the grid wire. In this paper after making a conformal transformation, from the plane $w$ to the plane $z$, where $w=logz$ and making an approximation which is sufficiently accurate for all diameters of grid wire up to 1/3 the spacing, formulas are derived which give results in good agreement with the values determined from two series of actual tubes for which the older formulas are greatly in error or fail entirely.