GB345918A - Improvements in or relating to duplex radio communication - Google Patents

Abstract

345,918. Duplex wireless signalling. TELEFUNKEN GES. FœR DRAHTLOSE TELEGRAPHIE, 12, Hallesches Ufer, Berlin. Aug. 23, 1930, No. 25240. Convention date, Sept. 16, 1929. [Class 40 (v).] Duplex signalling particularly on short waves is effected on a single wave-length by employing an aerial one wavelength long and by coupling the receiver to the aerial at a point which is a nodal point for the oscillations fed by the transmitting generator. Fig. 1 shows the current distribution along a straight aerial when excited by received waves a and by a transmitting oscillator b, the wavelength in both cases being equal to the aerial length. Transmitter oscillations, fed inductively from S at a point a quarter wave-length from one end of the aerial, create a current node at the midpoint of the aerial, and a receiver E coupled inductively at that point will be affected by received oscillations, but not by the transmitter. If capacity coupling is employed, the transmitter coupling is located at a voltage antinode, e.g. at one end of the aerial ; the receiver being either coupled inductively at the mid-point, or coupled by capacity at a quarter wave-length from one end.