| 摘要 |
244,121. Telefunken Ges. f³r Drahtlose Telegraphie. Dec. 6, 1924, [Convention date]. Thermionic generators; directive signalling.- A short-wave valve transmitter comprises a number of power amplifiers connected in parallel to a common plate or aerial circuit, and with their grid circuits excited by the several phases of an n-phase source. As shown in the Figure, an oscillator H is coupled to an artificial line K, and the grid circuits E, F, G of the three valves A, B, C are coupled to the line at points giving 120‹ phase displacement. The common aerial or plate circuit D is tuned to a frequency three times that of the source, and the valve grids are biassed by a battery so as to pass current during only one-quarter period of the higher frequency. For directive working, a number of spaced aerials are employed, a set of valves such as A, B, C is associated with each aerial, and the grids of these valves are excited in different phases by coupling the grid circuits of each set to an artificial line K, these lines being connected in series and energized by the source H of lower frequency. The artificial lines may be omitted if standing waves of suitable length are created in the cable by the current supplied by the source H.
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