Type 6BN6 is a late 1940s 'gated beam' FM discriminator. Where a relatively cheap quadrature coil can be used in place of more expensive wound components that are required for other discriminator circuits.
A diagram of the electron path in a 6BN6 gated beam valve.
The electron path is from right to left.
The base with all the internal details hidden by the metal plates.
The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 57 mm tall.
References: Data-sheet & Brian Cuff. Type 6BN6 was first introduced in 1965. See also1965 adverts.
