The whole point of the 6L7 design is to ensure maximum isolation between oscillator and signal, and to provide a mixer which is efficient at VHF where stable oscillation would usually require a separate VHF oscillator triode.
The oscillator injection needed to be 18 Volts peak to peak. The signal feed to the top cap is typical of the period to improve signal isolation.
The previous test results.
The Ken-Rad name and Made in USA.
The thin metal tube envelope is 25 mm in diameter and, excluding the IO base pins, is 63 mm tall.
References: Data-sheet, 1040 & 1043. Type 6L7 was first introduced in 1936. See also1936 adverts.
