The White valve like the Round valves were soft valves. That is they operated with a low pressure gas to obtain sensitivity. The physical size of these valves was dictated by the need to maintain a correct ratio of gas (mercury vapour) to electrode size for proper operation.
Tyne1047 dates the White valve to 1916. The White valve was used in the Mark III Amplifier which was designed by the UK Signals Experimental Establishment for field use and was first made in April 1917. The amplifier used two valves the second being a De Forest Audion. It is reported that the White valve proved erratic in operation.
At the same time the French TM hard valve was proving to be a better choice for military communications. The gain was less but the characteristics were more stable and less skill was needed in their operation. Subsequently the British made over 100,000 R Type valves, directly equivalent to the TM.
The grid connection is via the base shell with the filament connected by the base studs. The anode connects to the top cap.
The screw top cap was in use on valves until the early 1930s when the top hat connection was introduced.
The grid rests in the shoulder at the top.
A closer view showing the anode plate with the connecting wire on the underside.
Here the copper grid plate can be clearly seen as can the white coating on the filament.
The two grid supports are both firmly anchored in the pinch.
Photo micrograph of the grid plate. The lines in the grid holes show that they were stamped out of a solid sheet. The support wires pass through the holes and are folded to grip both sides.
The filament is welded to the side supports and is oxide coated. The coating used by Round was lime that decomposed to calcium oxide when heated during pumping. It is possible that White did the same.
One end of the filament with the spherical fixing bead at the junction with the support.
The other end of the filament showing the oxide clinging onto the support.
The balloon envelope is 60 mm in diameter, and including the base is 154 mm tall.
Reference: 1047. Type White was first introduced in 1916. See also1916 adverts.
