GB477304A - Improvements in tunable high-frequency electric coupling circuits - Google Patents

Abstract

477,304. Valve circuits for receiving wireless signals. HAZELTINE CORPORATION. March 19,1936, No. 8271. Void. Convention date, April 26, 1935. [Classes 40 (iii) and 40 (v)] Relates to means for coupling an aerial circuit to a wireless receiver in such a way that the overall gain is high and constant throughout the tuning range. The invention is described with reference to the ganged tuning circuits of a supersonic heterodyne receiver. The aerial is coupled to the input circuit of the pentode amplifier V1 by the common capacities Cs (furnished by the shielded lead-in S) Cp and Cc. Cc may be fixed but as shown is a variable condenser of the same design as the tuning condensers Ct, C2, C3. Owing to the presence of the coupling capacity in series with the tuning condenser in the input tuned circuit the effective capacity of that circuit differs from that of the circuit 10. The total coupling capacity is made as nearly as possible equal to Ca {R2/R - 1} where Ca is the antenna capacity and Ra and R are the respective resistances of the antenna and the input tuned circuit. Values of L and L2 can be chosen such that the circuits C, 10 remain matched throughout the range. In the modification shown in Fig. 4, the rotors of the ganged condensers Ct, Cc can be earthed. Specification 312,354, [Class 40 (v)], is referred to.