GB169007A - Improvements in and relating to transmitting circuits for wireless telegraphy and telephony - Google Patents

Abstract

169,007. Macrorie, A. K., and Shearing, G. June 15, 1920. Thermionic modulating systems and apparatus; thermionic oscillation generators. - In a method of transmitting in wireless telegraphy and telephony in which the aerial oscillations are modulated by varying the grid potential of an oscillating valve, a circuit containing a two-electrode valve and an auxiliary source of current is connected to the grid and arranged to cause a current to flow through the grid leak resistance of the oscillating valve to increase the mean negative potential of the grid .and thus decrease the aerial current. The oscillating valve W, Fig. 2, has its anode C coupled to the aerial A through a condenser B, and its grid circuit inductively coupled to the aerial coil Q through the coil N and variable condenser P. The two-electrode valve H is connected to the grid D and in series with the secondary L of a transformer, in the primary circuit of which is an alternator. During part of one half of each cycle the filament of the valve H becomes sufficiently negative to cause a current to flow through the valve and through the grid leak resistance G. In an alternative arrangement, the two-electrode valve is connected in series with a high-voltage battery and a signalling key, the closing of the key rendering the filament negative as described above. For telephony, a microphone and battery replace the alternator shown in Fig. 2. The grid leak resistance may be made inductive to lessen the abruptness of the growth and decay of the aerial current.