The RCA 8011 radar power triode was designed for 300 MHz (100 cm) operation in pulse mode. The VT90 was the original 'micropup' from M-OV that made airborne Radar a practical proposition and this exhibit carries both Type designations.
The VT90 was developed from the DET12 first as a co-axial version of the original valve with a Type designation of E1029 and later as the E1046 it produced pulses with a 5 kW peak power.
Given the history claims that the VT90 came first this RCA version would be a copy of the design. M-OV had close ties to RCA and America had much greater manufacturing capacity than the war torn UK.
The construction is co-axial and the anode is finned to enable forced air cooling. The grid is connected to the pin at the right in the picture. The filament connects at the left and the finned anode is seen at the centre.
These valves that were developed for military applications prior to the outbreak of war had no commercial use or Type designation. Thus VT90 is transmitting valve 90 for the UK air force the RAF.
The UK navy used M-OV 'micropups' in their type 284 fire control radar that operated at 600 MHz.
The VT90 was used in the AMES11 and AI radars.
The VT90 designation and the old stores code of 10E/97B. The central anode finned section is 36 mm diameter and 32 mm long including the clamping ring.
The filament leads.
The grid connection.
In essence a simple design of three concentric electrodes with an external anode allowing ease of cooling.
The thin glass tube envelope is 17 mm in diameter and, including the base, is 116 mm long.
References: 1005 & R J Sutherland Type 8011 was first introduced in 1939.