GB864444A - A circuit connection for the input circuit of a receiver - Google Patents

Abstract

864,444. R.F. couplings. TESLA NARODNIPODNIK. Jan. 9, 1959, No. 882/59. Class 40(7) The aerial input circuit of a radio receiver comprises, in series in the aerial connection, a blocking capacitor 6, a parallel tuned circuit 4, 5, and a coupling capacitor 3. The capacitor 3 is associated with the coil 1 and adjustable tuning capacitor 2 in the grid circuit of the first valve of the receiver. An A.V.C. voltage may be applied through resistor 7 as indicated. The circuit is suitable for use in the medium waveband and the component values are chosen so that a series resonant condition exists in the wanted range of signal frequencies in respect of the parallel circuit 4, 5, and the coupling capacitor 3. The circuit 4, 5, is arranged to be resonant . to reject unwanted signals, notably the image frequency band if the receiver is of hetrodyne type. Fig. 3 shows a development of the circuit of Fig. 2 arranged so that the medium waveband can be divided into two parts. Over one part of the band the switches 11 and 12 are positioned as shown so that the whole of inductor 4 is used in circuit 4, 5 and circuit elements 7, 8 are in series with coupling capacitor 3 and tuned by capacitor 2 in the valve grid circuit. In the other part of the band the switches 11 and 12 are moved to their other positions, only a portion of inductor 4 is used, and elements 9 and 10 replace elements 7 and 8. This arrangement makes it possible to reduce the capacity of the tuning capacitor 2 and increase the grid circuit impedance and the input circuit gain.