The 6BY6 is a miniature heptode. This is used as a synchronous detector, and the local oscillation from a separate source is applied to g3 (the second control grid).
The RCA Name and the Type designation placed at the top.
The RCA logo.
Looking along the grid axis. The solid screen hides the inner details.
The thin glass tube envelope is 17 mm in diameter, and excluding the B7G base pins is 48 mm tall.
Reference: Data-sheet. Type 6BY6 was first introduced in 1954. See also1954 adverts.
