GB548301A - Signal collecting systems for radio receivers and the like - Google Patents

Abstract

548,301. Wireless receiving apparatus. JOHNSON LABORATORIES, Inc. Feb. 19, 1941, No. 2278. Convention date, Feb. 19, 1940. [Classes 40 (iii) and 40 (v)] A signal collecting system comprises an exposed inductive element inductively reactive throughout the tuning range, a fixed condenser and a transformer having an adjustable core adapted to tune the secondary winding and the fixed condenser to resonance. In this way when a small primary is used the falling frequency coupling characteristic of the transformer may compensate for the rising characteristic of the loop 1. A small coupling capacity between the high potential ends of the transformer windings may be used, Fig. 3 (not shown). Alternatively synchronous tuning of circuits 1, 2 and 3, 5 may be secured by tight coupling between the primary 2 and secondary 3 so as to cause a negative reactance to be reflected into the circuit 1, 2. When the primary circuit is tuned in this way the connection of the loop 27 to the transformer 28, 29 is preferably, as shown in Fig. 7, such that the reflected negative reactance is in series with the loop reactance and is shunted by the transformer mutual inductance, Fig. 8 (not shown). The mid point of the loop, Fig. 4 or the mid point of the transformer primary, Fig. 5 (not shown) may be earthed instead of the end of the loop so that the loop is balanced with respect to the capacitive field to prevent pick-up by the electrostatic signal component. The Specification gives inductances values and winding data for the coils and design formulae. Specifications 366,475, 455,573, [Group XXXVI], 547,369 and 548,695 are referred to.