GB224574A - Improvements in or relating to wireless signalling systems - Google Patents

Abstract

224,574. Wells, R. I., Crowther, H. L., and Hecht, N. F. S. June 14, 1923. Thermionic modulating systems and apparatus. -Relates to thermionic vaive transmitters of the kind in which keying is effective through an auxiliary valve arranged as a grid leak to the main valve, and consists in arrangements whereby the grid potential for the auxiliary valve is applied directly from a source of alternating current (which may be the main valve itself), the necessary rectification being effected solely by the auxiliary valve. The key is inserted between the grid and filament of the latter valve. (1) Thus the main or power valve 3, Fig. 1, energizing the aerial 5, may have in its grid circuit the filament plate space of the auxiliary or grid leak valve 8 in shunt with a condenser 7, alternating potential being supplied to the grid of the grid leak valve by a transformer 9 in series with a condenser 10. The rectifying action of the valve 8 establishes a blocking charge on the grid of the main valve, and this is discharged, permitting transmission to take place, when the key 12 is depressed. In further examples : (2) the parts 9, 10 may be omitted, the oscillations of the main valve establishing the necessary blocking charge. This, however, gradually leaks away owing to imperfect insulation, so that intermittent groups of oscillations occur. (3) To prevent these the condenser 10 of Fig. 1 may be retained, the transformer 9 being dispensed with or replaced by a simple choke coil. (4) To make the charging of the main grid more definite, in the arrangement of Fig. 1, the transformer mav be replaced by a coil shunted by a condenser and coupled directly to the aerial. (5) Where the grid current of the main valve is large, the key 12, Fig. 6, shunted or not by condenser 10 and choke 13, may be connected between the grid and plate of the grid leak valve. In this case a grid leak resistance 16 with shunt condenser 15 is added.