The ECC85 is the definitive double triode for the front end stages of FM radio receivers. It was designed specifically for the purpose. This exhibit is a copy of the original design, and was produced by the distinguished Hungarian company of Tungsram. I believe that Philips had a connection with Tungsram as well as owning Mullard.

The two independent valves are screened by a rectangular plate across the diameter of the envelope. One triode would be used as an RF amplifier and the other as the local oscillator. The oscillator would be run 10.7 MHz lower than the incoming signal, and in the mixer a standard 10.7 MHz IF would be produced.

Is was popular in the late 1950s to add an FM radio board to a television receiver as well as to make dedicated band two receivers.

The thin glass tube envelope is 20 mm in diameter and excluding the B9A base pins the valve is 46 mm long.

 
Pin Connections

B9A	1	2	3	4	5	6	7	8	9
	a(2)	g(2)	k(2)	h	h	a(1)	g(1)	k(1)	s

 
Absolute Maximum Operating Conditions

Triode	Vh	Ah	Va	Vg	mAa	ra	gm
	6.3	0.435	250	-2.3	10	9700	5.9

Thanks to Frank Philipse for supplying the above datasheet

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