Identifier: abcofvacuumtubes00lewi (find matches)
Title: The A B C of vacuum tubes in radio reception; an elementary and practical book on the theory and operation of vacuum tubes as detectors and amplifiers. Explains non-mathematically the fundamental principles upon which all vacuum tube circuits are based. Includes practical circuits and practical questions and answers. It is written especially for the beginner. All electrical and radio terms are fully explained
Year: 1922 (1920s)
Authors: Lewis, Elmer Hugh, 1889-
Subjects: Vacuum-tubes Radio Radio
Publisher: New York, Norman W. Henley Pub. Co.
Contributing Library: Boston College Libraries
Digitizing Sponsor: Boston Library Consortium Member Libraries

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
y be pointed out here that thenormal potential of the grid with respect to the filament isalways zero. During a group of oscillations the negativecharge on the grid is built up to a comparatively largevalue and, unless the charge leaks off of the grid, the gridpotential will not be zero at the beginning of the next groupof oscillations. During the group of oscillations just con-sidered the operating point has slid down the characteristiccurve. If this negative grid charge does not entirely leakoff, the next group of oscillations will cause the negativegrid potential to increase and the operating point to slidestill further down the curve. It is obvious that the cut-offgrid potential might be reached and the plate current stoppedentirely. When this happens the tube is said to be blockedor choked. It is paralyzed until the grid charge is allowedto leak off, for example by placing the ringers on the gridterminal. It is quite necessary, therefore, to provide a path VACUUM TUBE DETECTOR 69
Text Appearing After Image:
One Train ofRadio FrequencyAntenna Oscillations Fig. 26—Rectification or detection of damped oscillations with a grid condenser. 70 ABC OF VACUUM TUBES through which the negative charge may leak when it becomeslarge, so that the grid potential may be returned to zeroand the plate current to normal in time for the next group.This may be accomplished by connecting a resistance calleda grid leak resistance across the grid condenser terminalsor directly between the grid and the filament. The value ofresistance must be high enough to prevent any great flow ofcurrent through it until the maximum charge has accumulatedupon the grid. It should not be too high, however, because thecharge would not then leak off quickly enough, but might accu-mulate until it leaks off through the glass walls of the tube, thedielectric of the grid condenser or the vacuuous space betweenfilament and grid. This might cause a thumping noise in thetelephone receiver. In the next section tubes containing gas are de

Note About Images