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Show Few Chanrjas Have Eeei Made in Radio C:rcui Unlike the various electrical instr ' Clients they represent, circuits used lj radio receiver consl ruction have should mo great basic change since the ir less art emerged from Ihe laboratory .stage. There have been elaborai ions anr ''improvements without end. but a dii. '"gram of the modern receiver shows 'that it is surprisingly similar lo Ihe ll'iirliesl models. In fact the method err coupling the circuit of one tube to ,ipnt of another Is pracl illy Ihe same oday as il was when inlics were ';ri 'levlsed. Oilier sections of Ihe hookup Uave changed only in kerpmc with inie increasing number of tubes atd PIther apparatus. :) one of Hie circuits first lo become nopular with the liome-huihlins en-anisiasi en-anisiasi was Ihe regenerative. Il bad 'imerous variations. Il still is in ex-e'etice ex-e'etice in "e mod:- receiver. :1-i,Uougb :1-i,Uougb somewhat dis.uised. Il Is now ''ece.b'd. as a rule, with a stop of oVd radio frequency ampli MVat ion. hatainiug all of lis advantages with thfd. d s-'ieciivi'y. -Tbe'hve-liibe tuned radio frequemy receiver and its co-models of a greater great-er number of tubes, is another that; has shown no revolutionary change. It consists entirely of a series of circuits known as the "simple audion" with various systems of oscillation control. The simple audion layout was first used with the development of the vaccum or audion tube. It provides a method of connecting the tube to its batteries and accompanying condensers and coils. Also it does not show a great difference from the wiring arrangement ar-rangement of a crystal set. In analyzing a . modern eight-lube radio frequency amplifier the fact that it is merely an elaboration of the live-tuber live-tuber is quickly apparent. It, too, consists con-sists of a series of audion circuits with changes made to accommodate added equipment necessary lo maintain main-tain the receiver in balance. The superheterodyne, which sprung into popularity along wilh the tuned radio frequency type, also goes back to the audion and the regenerative. These two are combined with long or short wave radio frequency amplification amplifica-tion to tlie point where great selectivity selectiv-ity and volume result. In some cases tuned radio frequency amplification has been added to improve the receiver. |