Osram R4



Introduced in 1917

The R.4 was a hard vacuum valve developed from the R type to meet a specific need for a heterodyne receiver. See also: R2 
The lettering on the envelope reads: Valve wireless receiving R.4 Pat. No. 4411. A10528. The other side reads: Osram GEC Made in England. R.4. The Naval version is the NR4.


Vf Af Va Vg mAa ra gm
3.3 1 20 -1 2.5 30,000 0.2

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