GB524499A - Tunable coupling system for wide band amplifiers for short and ultra short waves - Google Patents

Abstract

524,499. Transformers and inductances. RADIOAKT.-GES. D. S. LOEWE. Oct. 25, 1938, Nos. 30834 and 30835. Convention dates Oct. 26, 1937 and Dec. 18, 1937. [Class 38 (ii)] [Also in Group XL] A tunable coupling system for wide-band amplifiers for short-waves etc. comprises tuning coils 1, 2 screened from each other as far as direct capacitive coupling is concerned and coupled together by a condenser 7 or by stray capacity between parts of the circuits, the tuning being varied by highly conductive cores 5, 6 movable within the coils. The cores may comprise insulated copper tubes which fit closely inside the coils and are mechanically connected with each other. The circuits may be further coupled by coils 1a, 2a. The coils 1, 2 may be end-to-end, Fig. 3 (not shown) on a former inside which the cores 5, 6 are attached to opposite sides of the same endless belt. Screening arrangements. The symmetrically arranged screening system may comprise, in addition to outer screens 17, 17', 18, 18<SP>1</SP>, Fig. 4. a metallic sheet 16 which is level with the middle of the valves 15 and of the tuning coils 1, 2 (with adjustable copper or like cores). The capacitive coupling located at 7, Fig. 1, is constituted by two condenser plates 19a, 19b, Fig. 4, on opposite sides of a hole 20 in the screen. The capacity can be varied by closing the hole more or less with an earthed plate 21. The screens 17, 18 are for couplings with further stages, Fig. 5 (not shown). Tuning heterodyne oscillators. The relation between frequency and setting of the intervalve coupling is as shown in Fig. 6, where h denotes the position of the cores 5, 6. To facilitate tracking, this characteristic can be initiated approximately in a heterodyne oscillator 0, Fig. 7, by means of condensers arranged as shown and having circular plates.