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BELL SYSTEM TECHNICAL JOURNAL 



range of the negative grid oscillator can be extended beyond 1200 

 megacycles. 



Tubes for Receiving Purposes 



For receiving purposes where large outputs are not needed, the ultra- 

 high-frequency requirements may be met by shrinking all the tube 

 dimensions in proportion to the desired wave-length. Tubes con- 

 structed by Thompson and Rose ^ based upon this principle are shown 

 in Fig. 13 compared in size with the conventional receiving type tube. 



Pig. 13 — Receiving tubes of extremely small dimensions. A conventional receiving 

 type tube is shown at the right for comparison. 



These tubes make use of parallel plane electrodes, the cathode being 

 oxide coated and indirectly heated, and the grid being in the form of a 

 mesh. A cross-section view of the triode is shown in F'ig. 14. This 

 tube will oscillate at frequencies up to 1000 megacycles in miniature 

 replicas of the customary circuits used at longer wave-lengths. A 

 photograph of a complete oscillator is shown in Fig. 15 and the circuit 

 diagram in Fig. 16, 



