GB488566A - Improvements in superheterodyne receivers - Google Patents

Abstract

488,566. Valve circuits for wireless reception. RADIOAKT.-GES. D. S. LOEWE. Jan. 8, 1937, No. 625. Convention date, Jan. 13, 1936. Addition to 458,147 and 458,149. [Class 40 (v)] In a superheterodyne receiver in which radiation is prevented as described in the parent Specifications by feeding potential of opposite phase to the grid of the potential applied from the oscillator through inter-electrode capacities a second bridge circuit is provided one diagonal of which is connected between the cathode of the frequency changer and earth while the other diagonal is connected across the tuned circuit of the local oscillator. Fig. 1 shows a frequency changer in which the circuit of the local oscillator is tuned by the condenser 7a, 7b whose junction is connected to the cathode. Radiation due to coupling 13 is neutralized by condenser 12. A resistance 24 may be connected in series with the grid, or alternatively a resistance may be provided in parallel with condenser 7b to ensure exact phase opposition, or the oscillator may be a tetrode or pentode having a large anode impedance. The second bridge circuit is constituted by condensers 7a, 7b and differential condenser 17, 18, 19 which has a capacity equal to the capacity 10 between the grid 3 and the cathode. Fig. 3 shows an arrangement in which the balancing condenser 12 is dispensed with and the cathode is arranged to be in opposite phase to the oscillator grid by adjustment of the differential condenser.