. Practical wireless telegraphy; a complete text book for students of radio communication . ctrode to the positive pole of the Shoemaker has discovered that the large electrode may be of zinc, and if the smallplatinum point and zinc are immersed in a dilute sulphuric acid solution, the cell not onlyacts as a detector of oscillations, but supplies its own local E. M. F. as well. In this formthe detector is termed a primary cell detector. 142. The Three Element Valve Detector.—A modified type of the twoelement Fleming valve is the three element valve, the circuits for which are shownin F
. Practical wireless telegraphy; a complete text book for students of radio communication . ctrode to the positive pole of the Shoemaker has discovered that the large electrode may be of zinc, and if the smallplatinum point and zinc are immersed in a dilute sulphuric acid solution, the cell not onlyacts as a detector of oscillations, but supplies its own local E. M. F. as well. In this formthe detector is termed a primary cell detector. 142. The Three Element Valve Detector.—A modified type of the twoelement Fleming valve is the three element valve, the circuits for which are shownin Fig. 179. From the viewpoint of mechanical construction, it is practicallyidentical with the Fleming valve, with the exception that a metallic element knownas a grid is placed in the path of the electrons flowing from the filament to theplate. This grid may be made up of a zig-zag shaped platinum wire or a plate per-forated with holes, or in certain types of valves it consists of a spiral of filament may be constructed of tungsten, tantulum or platinum. The circuit generally. Fig. 179—Fundamental Circuit for Valve. the Three Element Oscillation \ / adopted for the three \ element valve appears in Fig. 179, where the pri-mary and secondary cir-cuits of a receiving tunerare represented by theusual notations and thegrid, plate and filamentof the valve by G, P, andF, respectively. An im-portant part of this cir-cuit is the so-called gridcondenser C-1, whichgenerally has low capa-city, varying and .0005 micro-farads. In addition to thelighting battery B-1,which is generally of 4volts, a local batteryB-2 of 35 to 200 voUshas its positive terminalconnected to the plate P and the negative terminal to the telephones P-1, which are in turnattached to the positive end of the battery B-1. The secondary terminals of the receivingtuner are connected to the negative terminal of the filament and to the grid. In this form of valve as in that already described, the in
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecttelegra, bookyear1917
