GB205117A - Methods of receiving in telephony by high frequency oscillations and in wireless telegraphy and telephony - Google Patents

Abstract

205,117. O'Dell, A. E., (Lorenz Akt.-Ges., C., and Scheppmann, W.). April 7, 1922. Receiving systems; thermionic amplifiers and detectors.-Receiving systems are made very selective by avoiding as far as possible capacity, other than that of the antenna, across the aerial tuning inductance. This inductance is wound in one or more layers of very fine wire on a long cylinder and may have an iron core. Variations in inductance are effected by arranging a movable copper cylinder round the coil. The resistance introduced by the fine wire and the losses in the copper cylinder are counteracted by the use of back coupled valves in both primary and secondary circuits. As shown, a small series condenser c<1> is provided and the aerial inductance is wound of fine wire as described above. The reaction coil s<2> is arranged to reduce as far as possible the effective ressitance of the antenna at the desired frequency. The secondary circuit is loosely coupled and includes a back coupled valve R<2>. For tuning purposes the telephones i may be included in the plate circuit of the valve R<1>, but during reception they are in that of the valve R<2>. The coil s<5> supplies local energy for heterodyne working, or a circuit containing in series a detector, an interrupter, and the telphones may be coupled inductively to the secondary current. Specifications 101,541 and 101,702 are referred to.