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ID = 17238
Great Britain (UK)
Brand: Common type Great Britain tube/semicond.
Tube type:  Transmitting Triode, air cooled 
  Ca. 1925 up to 1945 very rare. ***
Identical to NT57T = CV1234 = W560
First year Apr.1939 -- Original-techn. papers.
Predecessor Tubes NT57D   NT57  

Base Wires Wires only.
Was used by Radar
Filament Vf 9 Volts / If 35 Ampere / Direct

NT57T silica valve, with anode (left) and grid (right) wire connections at the top, and filament at the bottom, also wire connections only. This valve has two 'hairpin' filaments, each with a pair of wires. The NT57T is the thoriated filament version of the NT57, the first valve to be made specifically for use in radar. The NT86, developed from the NT57T, had three filaments. The use of thoriated tungsten resulted in the increase of cathode emission to 18 A from the 5 A emission of the NT57. Heating power was about 300 W against the some 700 W of the NT57.

Silica glass has a very high melting point (between 1500 and 1700 C) and a low coefficient of thermal expansion. Normal glass softens at around 450 C. Because of these properties, silica glass does not crack by heat.

The picture of this valve features on the cover of the August 2003 issue of "The Collector", published by the "Tube Collectors Association".

Early samples of the NT57T were made and tested in April 1939 into a Type 79 early warning radiolocalization set at the HM Signal School in Portsmouth. By September 1939 the tube was in small-scale production at Signal School and MOV.

Also known as 10E/93

Information source Taschenbuch zum Röhren-Codex 1948/49   Callick, Metres to Microwaves
NT57T: Private collection
Emilio Ciardiello

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