DESIGN FACTORS OF THE 1553 TRIODE 



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that has been previously gold sputtered. The winding tension is held 

 within ±1 gram weight to about 15 gram weight, which is about sixty per 

 cent of the breaking strength of the wire. This is accomplished by means 

 of a small drag-cup motor brake, a new method which was developed 

 especially for these fine grids. The grid is then heated in hydrogen to 

 about 1100°C, at which point the gold melts and brazes the wires to the 

 frame. The mean deviation in wire spacing is less than about ten per 



Fig. 4. — Physical appearance of the elements comprising the 1553 triode. 



cent, and in fact these grids are fine enough and regular enough to be 

 diffraction gratings as is shown in Fig. 5. In this figure, a fourth order 

 spectrum diffracted by one of these grids can be seen. The third order, 

 which should be absent because the wire size is about one-third of the 

 pitch, is much less intense than the fourth. Proper spacing of the grid is 

 then obtained by a thin copper shim placed between the cathode ceramic 

 and the grid frame. Its thickness must be equal to the coating thickness, 

 plus the thermal motion of the cathode, plus the desired hot spacing. 



