GB307989A - Improvements in and connected with radio telegraph, telephone and like signalling circuits and apparatus - Google Patents

Abstract

307,989. Watkins, A. E. Dec. 21, 1927. Thermionic amplifiers.-A coil unit for wireless receivers for the alternative reception of medium and long waves comprises an inductance c o i l formed in sections L<1>, L2, Figs. 1 and 4, and a reaction coil also formed in sections R<1>, R<2> alternating in position with the coils' L<1>, L<2> ; a switch S, Fig. 4, being provided for short-circuiting the loading- coil section L<2> when medium waves are to be received by the other coil L<1> alone. The smaller reaction coil R<1> is interposed between the low-potential end of the coil L<1> and the highpotential end of the coil L<2>. The two coils L<1>, L<2>, when both are in circuit, are connected in series and shunted by a tuning-condenser VC, and the reaction coils are permanently connected in series, the reaction being controlled by a series condenser RC. Fig. 4 shows the coils unit arranged as a tuned-anode coupling between a high-frequency amplifier and a detector valve, but it may also be used as an aerial input to a detector valve. The plate of the detector valve may be connected through a high-frequency choke to a tap on an iron-cored choke, which at one end is connected to the HT supply and at the other end to a condenser leading to the grid of an audio-amplifier.