R2_England

OSRAM G.E.C. Wireless Receiving No. R.2. After 1919, manufacture was by the M.O. Valve Company.

Soft valve of similar internal construction as the French TM. Initially filled with Nitrogen to 0.06 mm Mercury. From September 1917 on Helium was used at a pressure of 0.6 mm Mercury. Produced by BTH, GE(Osram),and Ediswan.

An R2 was exhibited by MOV at the Physical Society in London in 1920.
The filament rating is stated as 3.5V at 1.2A and was nitrogen filled.
The E12 base was for the filament wires and the plate and grid were from wire leads on the top of the valve. First made by Osram GEC June 1917. This tube was a successor to the BTH Audion which had manufacturing difficulties.

Giorgio Basil: British-made replacement for the de Forest audion. The BTH audion was developed in 1916 and the design of the R.2 came out of that work when BTH abandoned the audion physical design in 1917 and based the new valve on the French TM or hard valve. The R.2 was a nitrogen-filled valve with a gas pressure of initially 0.0045 to 0.5 mm of mercury (Hg) and eventually 0.06 mm Hg.

R.2 production commenced at Osram in June 1917. It was soon found that the nitrogen was absorbed by the internal electrodes, which reduced the gas pressure in the envelope. Various other gases were tried: first argon, but the gas ions caused premature disintegration of the tungsten filament. Eventually, helium was found to give a consistency of performance: it was not absorbed by the electrodes and did not cause damage to the filament. Because helium is a lighter gas than nitrogen, a higher gas pressure of 0.6 mm Hg was required. The helium-filled valve was designed R.2A.

• Filament: drawn tungsten wire of length 20 mm and diameter 0.083 mm, operating at 3.5 V, 1.2 A.
• Anode: nickel sheet bent to a complete cylinder of lenght 15 mm and diameter 9 mm, operating at 25 to 40 V.
• Grid: helix of molybdenum wire of 0.4 mm diameter, pitch 5.5 turns/cm, length 18.5 mm and mean diameter 4.5 mm.
• Base: candelabra cap.

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