GB286792A - Improvements in circuits and apparatus for use in amplifiers working at radio frequencies - Google Patents

Abstract

286,792. Cleaver, R. L. Dec. 11, 1926. Coupling aerial and detector circuits; thermionic amplifiers. - An input or intervalve coupling for a radiofrequency amplifier comprises two oscillation circuits with their coils closely coupled and an adjustable condenser or condensers in one or both circuits so arranged as to carry the tuning simultaneously through frequencies in two ranges of materially different value, e.g. in the ratio of 3 or 4 to 1. Fig. 2 shows an arrangement in which the first oscillating circuit comprises the lower half of the coil and the aerial capacity indicated by C, and the second circuit comprises the whole coil and the condenser C2. The anode coil L is tuned by condenser C5 in one range and acts as a choke in the other range. Fig. 3 shows an intervalve auto-transformer coupling with provision for neutralizing the valve capacity in which the two circuits are formed by the whole and half of the coil L with condensers C5, C1 respectively. In a modification, Fig. 6 (not shown) an inductive transformer coupling is employed. Fig. 5 shows an alternative inductive transformer coupling in which the secondary has two periods of oscillation the coil L with the resultant of condensers C1, C<5>, C8 in parallel and the two halves of the coil with condensers C1' C8 which form two tuned circuits in parallel. In a modification, Fig. 7 (not shown), an inductively coupled transformer is employed with tuned condensers connected across both the primary and the secondary, the primary being tuned to one frequency and the secondary to the other. Specification 28826/04 is referred to.