The 6K8G is the classic triode hexode frequency changer or mixer for broadcast receivers.
This exhibit has a clear glass bulb and would rely on external shielding where other mixers had external zinc paint sprayed on to provide screening. For isolation of the signal input and output circuits the hexode signal grid is taken to the top cap.
A diagram of the construction can be found in 6K8.
The Type designation within an octagon on the envelope.
The pinch and lower connections. The grid pitch can be seen from the notch spacing.
The cathode is offset to one side. The triode control grid is on the left with the anode on the extreme left. The mixer is to the right.
The top view. The triode anode is nearest the bottom of the image.
The classic envelope is 38 mm in diameter and, excluding the IO base pins, is 98 mm tall.
References: Data-sheet & 1040. Type 6K8G was first introduced in 1938. See also1938 adverts.
