The VHT4 is a frequency changer of heptode construction dating from the early to mid 1930s. The UK built heptodes followed the lead of the American manufacturers with their Pentagrid converters.

The oscillator voltage needs to be 15 Volts peak to peak for correct operation. The triode oscillator is formed between the cathode and grid2 with g1 as the control grid. The signal injection control grid for the mixer part of the single electron stream is to g4 on the top cap.

The classic envelope is 42 mm in diameter and, excluding the B7 base pins, is 106 mm tall.

 
Pin Connections

B7	1	2	3	4	5	6	7	tc
	g2	g1	g3,g5	h	h	m,k	a	g4

 
Absolute Maximum Operating Conditions

Heptode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	4.0	1.0	250	80	-3	2.6	5.1	0.5	0.7

Triode	Va	mAa
	100	1.2

This exhibit was last updated on 14 August 2005