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BELL SYSTEM TECHNICAL JOURNAL 



order to make the inter-electrode capacitances as small as possible, 

 transit times are increased. Fay and Samuel ^ in a recent paper 

 presented before the International Scientific Radio Union (U. R.S.I.) 

 describe a tube designed for use at 300 megacycles which well illustrates 

 this point. The tube is shown in Fig. 7. It differs from the one 



Fig. 7 — A tube for use at frequencies up to 350 megacycles. 



previously discussed in the close spacings between elements, par- 

 ticularly between the grid and filament. The lead length is further 

 decreased and lead diameter made considerably larger in order to 

 decrease lead inductance and resistance. The inter-electrode capaci- 

 tances are: 



Plate to grid 2.5 /x/uf 



Grid to filament 2.0 ixixl 



Plate to filament O.b? fi^i 



While these capacitances are substantially the same as for the tube 

 shown in Fig. 5, the limiting frequency, as set by circuit resonance, is 



