GB163070A - Improvements in aerial systems employed in wireless signalling - Google Patents

Abstract

163,070. Smith, S. B., and Wright, G. M. Dec. 24, 1919. Directive signalling; aerials. -A directional system giving the well-known heart-shaped polar diagram is obtained by connecting a pair of frame aerials through a tightly-coupled radio-goniometer F, S to one primary P of a transformer, and connecting the mid-point of the two frames to earth through a resistance R and a second primary T of the transformer. The secondary J is connected at one end to a screen E and is shunted by a variable capacity K by which the complete circuit can be tuned. Instead of two frame aerials and a radio-goniometer, a single rotatable frame may be employed, with its mid-point earthed through the winding T. In the modification shown in Fig. 3, the winding T acts on a secondary B in the circuit of the primary P, so that at the zero polar position there is no current in this circuit. In this case the transformer P, J is a loosely-coupled jigger, and a separate tuning capacity K<1> is introduced in the circuit of the primary P. The minimum polar indication is approximated to zero by adjustment of the resistance R, the best effect being obtained when the earthed aerial system is tuned to a wave-length rather shorter than that which is being received. Direction can be determined by adjusting the radio-goniometer until no change of signal strength occurs when the connections to the search coil S are reversed. This corresponds to the points X, Y on the polar diagram, Fig. 5, which are also the points at which a given change of angle makes the greatest difference to the two signal strengths. For standby purposes, the resistance R may be shortcircuited, giving a system which receives approximately equally in all directions.