ARMSTRONG, OPERATING FEATURES OF THE AVDION 243 



it; and^ second, to use a large inductance in the wing circuit, thereby- 

 tuning it to the incoming frequency (in conjunction with the capacity 

 between the filament and wing in the audion itself). Both methods may 

 be used together. Various methods of coupling grid and wing circuits 

 are shown. Methods of combined audio and radio frequency amplifica- 

 tion are described. 



The audion, being a generator of alternating current of any desired 

 frequency, can be used as a beat receiver. A steady audion generator of 

 regular groups of radio frequency oscillations is illustrated. Various 

 methods of audio frequency tuning permitting high selectivity are pos- 

 sible. By the use of two audions in cascade, amplifications as high as 

 1,000 are attainable. The cascade systems can be arranged so as to 

 operate both audions either synchronously or non-synchronously. 



As an alternative to beat reception of sustained wave signals, an ar- 

 rangement is explained, wherein the amplifying 'ratio of a repeating 

 audion is varied periodically at an audio frequency. Coupled to this 

 system is a simple audion detector. Musical signals of any desired pitch 

 are thus obtained. 



It is found that static of large amplitude nearly always decreases the 

 wing current, while a signal (with beat reception) alternately increases 

 and decreases it. A system of circuits is described whereby this fact is 

 taken advantage of in balancing out static while retaining the additive 

 response to signals, thus effecting an elimination of static to a consider- 

 able extent. 



Finally, instances of long-distance stations received and interference 

 overcome in practice are given. 



