The EF11 is a variable μ pentode with a base that Tungsram describe as Footless.
The code EF11 is directly related to the Philips code scheme (as used by Mullard), the base fitting into numbers not used in the UK.
This valve was intended for the IF amplifier of radio receivers.
The metal envelope is 35 mm in diameter and excluding the Footless base pins the length is 37 mm.
References: Datasheet & 1043. Type EF11 was first introduced in 1939.
Absolute Maximum Operating Conditions¶
Updated January 27, 2013. shape:wide.metal.tube construction:glass.disc type:pentode age:1930.1940 base:footless heater:6.3v pins:8 pin:1.g2 pin:2.g1 pin:3.k.g3.m pin:4.- pin:5.h pin:6.h pin:7.- pin:8.a