TRANSATLANTIC RADIO TELEPHONY 125 



In the design of high-power tubes for use in this system the main 

 problem is to insure the ready disposal of the large amounts of heat 

 generated at the anodes. For the conditions of use in the present 

 type of system where the tube is employed as an amplifier, the power 

 which must be disposed of as heat at the anode is of the same order of 

 magnitude as the power which the tube will deliver to the antenna. 

 In the case of the present equipment, therefore, the tube must be so 

 designed as to operate continuously with a heat dissipation at the 

 anode of more than 10 kw. It is obviously difficult to secure so large 

 a dissipation in a tube enclosed with glass walls, and a tube was 

 therefore designed in which the anode forms a part of the wall of the 

 containing vessel and the heat generated in it is removed by circu- 

 lating water. The tube used is shown in Fig. 6. The lower cylindrical- 

 portion is the anode which is drawn from a sheet of copper. The 



Fig. 6 



upper portion is of glass and serves both to support and insulate the 

 grid and filament elements. 



The three principal difficulties met in the construction of these 

 tubes are the making of a vacuum-tight seal between the copper and 

 the glass, the provision of adequate means for conducting through the 

 glass wall the large currents necessary to heat the filament, and the 

 obtaining of the necessary vacuum for high-power operation. 



