The EF11 is a variable μ pentode with a base that Tungsram describe as Footless.
The code EF11 is directly related to the Philips & Mullard code scheme, the base fitting into numbers not used in the UK. The pin number sequence is that used by Philips.
This valve was intended for the IF amplifier of radio receivers.
The wide metal tube envelope is 35 mm in diameter and, excluding the Footless base pins the is 37 mm tall.
References: Data-sheet & 1043. Type EF11 was first introduced in 1939. See also 1939 adverts.
Absolute Maximum Operating Conditions¶
Updated January 04, 2022.