Rod-Electrode Tube

a subminiature receiving electron tube with a directly heated cathode. In such a tube, the electrodes, or grids, controlling the electron flux are rod shaped. Their cross section is usually circular or rectangular. Rod-electrode tubes were developed during the 1950’s by V. N. Avdeev.

The rod electrodes (Figure 1) form electrostatic lenses that focus the electron flux and improve the current distribution in the tube. As a result, rod-electrode tubes may operate at the relatively low anode and screen-grid voltages of 6–60 volts (V). The voltage in high-power rod-electrode tubes may reach 120 V. Rod-electrode tubes consume less power than directly heated electron tubes with coil grids, although both types exhibit similar parameters

Figure 1. Schematic of electrode arrangement in a rod-electrode pentode tube: (A) anode, (C) cathode, (C,) control grid, (C¡) screen grid, (G₃) suppressor grid; the broken lines indicate the paths of the electrons

and characteristics. Rod-electrode tubes are designed for use in low-noise amplifiers operating at high (up to 200 megahertz) and intermediate frequencies and in mixers, oscillators, and output power amplifiers of radio transmitting stations operating on power supplied from batteries or storage cells. Since the introduction of semiconductor electronics, transistors have supplanted rod-electrode tubes in many applications.