OSRAM G.E.C. Wireless Receiving No. R.2
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.
After 1919, manufacture was by the M.O. Valve Company.
Hauteur • Height • Höhe : 84 mm • 3" 1/4
Diamètre • Diameter • Durchmesser : 50 mm • 2"
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