The 6K8G is the classic triode hexode frequency changer or mixer for broadcast applications here with a glass envelope rather than the original metal can 6K8. Later the glass tubular 6K8GT was manufactured.
For isolation of the signal input and output circuits the hexode signal grid is taken to the top cap.
The perforated outer screen and pinch components.
The special feature of the design can be seen from the top mica. Rather than a heptode where strong signals can 'pull' the local oscillator frequency or a separate triode oscillator, the cathode has the inner grid facing both towards the mixer and backwards to the oscillator anode. The 6K8 exhibit has a clear diagram of the construction.
The base of the oscillator anode.
The classic envelope is 38 mm in diameter and, excluding the IO base pins, is 99 mm tall.
References: Data-sheet & 1040. Type 6K8G was first introduced in 1938. See also1938 adverts.
