GB458147A - Elimination of radiation in the case of superhet receivers - Google Patents

Abstract

458,147. Valve circuits for wireless reception. RADIOAKT.-GES. D. S. LOEWE, 10, Wiesenweg, Steglitz, Berlin. March 9, 1936, No. 7018. Convention date, March 12, 1935. [Class 40 (v)] In a superheterodyne receiver radiation of the local oscillation due to the coupling between the signal and local oscillation control grids is compensated by potentials of opposite phase. Fig. 1 shows a hexode frequency changer, particularly for short waves, in which the signal is applied to a grid 3 screened from the grid 7 to which local oscillation is applied. Local oscillating energy fed from grid 7 to grid 3 is compensated by energy of opposite phase fed through condenser 18. The capacity between grids 3, 7 may be reduced by the provision of two screening grids 6, 6<1>. The condenser 18 is preferably screened and the oscillator 8 and frequency changer may be separately screened, as shown in Fig. 2, with only the aerial passing to the exterior, apart from the supply leads which are provided with chokes and earthing condensers, and the self-capacities within the screen are rendered invariable. The phase reversed energy fed through the condenser 18 may be fed to the aerial or to a tuned input circuit and the energy may be obtained from an auxiliary inductive winding coupled to the tuned circuit of the local oscillation generator, Fig. 3 (not shown).