GB737873A - Improvements in and relating to slot aerials - Google Patents

Abstract

737,873. Aerials. BRITISH BROADCASTING CORPORATION. Aug. 15, 1952 [Aug. 21, 1951], No. 19736/51. Class 40 (7). In a slot aerial system comprising a single longitudinal slot 11 on a collinear array of such slots in a vertical hollow conducting cylinder 10, a null in the normally circular horizontal directivity pattern is produced by disposing on or near the cylinder, one or more elongated conductors whose longitudinal axes are substantially at right angles to the longitudinal axis of the cylinder so that the resultant cardioid directivity pattern and the input impedance are substantially constant over a frequency hand equal to Œ 4 per cent of the operating frequency. When the conductors are mounted directly on the cylinder the points of connection are spaced from the points of maximum oscillatory voltage on the cylinder. The conductors may function as parasitic elements or they may be energized directly. As shown in elevation and crosssection respectively in Figs. I and 2, four 0.6# horizontal conductors 18... 21 are mounted on #/4 rods 14... 17 spaced vertically #/2 on the opposite side of the cylinder to the slot, the length of the slot being 2#, the diameter of the cylinder being #/8 and the transmitter or receiver 12 being connected by a balanced feeder 13 to the centre of the slot. The shape of the directivity pattern may be altered by varying the length of conductors 18 ... 21 and conductors 18, 21 may be of different length from conductors 19, 20. In another embodiment, Figs. 4 and 5 (not shown), four collinear pairs of #/5 horizontal conductors are spaced vertically #/2, the two conductors of each pair projecting from opposite sides of the cylinder, all the conductors being in the same vertical plane. Specification 543,471 is referred to. 737,917. Pulse and gating circuits. STANDARD TELEPHONES & CABLES, Ltd. Feb. 1, 1952 [March 28, 1951], No. 2734/52. Class 40 (6). [Also in Group XXXIX] An automatic exchange system (see Group XXXIX) includes the following: (a) a circuit, Fig. 5B, for producing a pulse at the end of a train of impulses representing a digit. The input of 8 kc. pulses amplitude modulated by the impulse train is applied to a lowpass filter 417 producing a negative pulse of the same duration as the impulse train. This pulse is differentiated and the resulting positive pulse operates a flip-flop circuit 419, 422 which supplies a pulse to the output lead 427. (b) A pulse delaying circuit, Fig. 5C. An 8 kc., 1 Ás. pulse series on lead 393 is gated through a tube 462 by a longer pulse on lead 427 and the first pulse to be gated passes through a tube 463 and a 1 Ás. delay line to a phantastron 464 producing a delay of 1000 Ás., and the cathode of which is coupled to the suppressor of the tube 463 to prevent the passage of further pulses. The resulting negative pulse is differentiated and the positive pulse so produced is lengthened and re-timed by a tube 471 enabled by the pulse series on lead 393. (c) A gating circuit, Fig. 5D. Each of ten gating circuits 644, 645 is connected to a common input lead 685, a common output lead 644A and the corresponding wire in each of two groups 117, 122 of ten wires. When a pulse series on the input lead 685 is coincident with a pulse series on a wire of the group 117, the condenser in the associated gating circuit is charged to produce a bias which allows any pulse series on the wires of groups 117, 122 connected to that gating circuit to produce a coincident pulse series on the output lead 644A.