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The VT90 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.

It 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 or VT90 that produced pulses with a 5 kW peak power.

See NT58 for the service version of the DET12.

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.

Part of the same series of valves was the CV55 (E1190) that produced pulses of 40 kW peak at 1,200 MHz.

The ACT19 is one of the few valves of this type that did get a commercial Type designation and it too was a forced air cooled pulse triode.

The CV15 is a smaller version of the VT90 with conduction cooling.

The valve is 40 mm in diameter and, excluding the base pins, is 111 mm long.

References: ¹⁰⁰⁵ & R J Sutherland Type VT90 was first introduced in 1939. See also 1939 adverts.