The EK3 octode frequency changer is set on the short lived side contact base. The local oscillator formed using a grid as anode would need to supply 17 volts peak to adequately modulate the main electron flow. The signal input to g4 is applied to the top cap for maximum circuit isolation. The frequency of use would be a few megahertz at best.
Our other EK3 has a much greater diameter envelope and is probably a later product. Clearly this valve has overheated in use.
The wide glass tube envelope is 33 mm in diameter and, excluding the Ct8 base pins, is 124 mm tall.
References: Data-sheet, 1040 & 1043. Type EK3 was first introduced in 1938. See also 1938 adverts.
Absolute Maximum Operating Conditions¶
Updated June 02, 2021.