Synthesis of Control-Grid Structure for Remote Cut-off Tubes from the Transfer Characteristic

Abstract

The basic guiding factor in the design of remote cut-off tubes is to fit the design to a preferred curve of transconductance versus control-grid voltage. Instead of the conventional method of achieving this criterion by winding the grid with a series of variable pitches, a new approach has been attempted by considering the tube to be made up of three tubes in one envelope, one tube of low mu having a grid of wide pitch, a second one of an intermediate pitch having medium mu and a third one of close pitch and high mu. The pitches of the three sections, derived on the basis of three characteristic design reference points on the transfer characteristic of a standard remote cut-off tube, agree closely with three of the major pitches used in the actual tube configuration. An attempt has also been made to compute the transfer characteristic for a remote cut-off tube fabricated with a grid structure of this type. The theoretical characteristic obtained after correction for transition regions and effective cathode area shows close agreement with the experimental one.