The 6K8 triode hexode valve was purpose designed as a radio frequency changer. The valve has a common cathode and is unusual within our collection in that the triode and hexode control grids are internally connected.

The local oscillator would produce 7.5 Volts peak to peak signal from the triode section.

The input signal would be coupled to the frequency changer via the top cap connection to grid 3.

As a metal enveloped valve the top cap connection is interesting. The connector is standard but is set in an insulating disk that is then sealed into a shaped end of the envelope. This appears quite difficult to manufacture.

The thin metal tube envelope is 25 mm in diameter and excluding the IO base pins, is 60 mm tall.

 
Pin Connections

IO	1	2	3	4	5	6	7	8	tc
	m	h	a	g2-g4	g(t)-g1	a(t)	h	k	g3

 
Absolute Maximum Operating Conditions

Hexode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	6.3	0.3	250	100	-3	2.5	6	0.6M	0.36

Triode	Va	mAa
	100	3.8

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 04 June 2007 {find valves by name}