GB501843A - Improvements in or relating to directional aerial systems - Google Patents

Abstract

501,843. Directive wireless systems; transformers. CORK, E. C., and PAWSEY, J. L. June 26, 1937, No. 17819. [Class 40 (v)] [Also in Group XXXV] A directional aerial system comprises two aerials each connected by a feeder to a common channel consisting of transmitting or receiving apparatus. The aerials are spaced apart by a distance large compared with the signalling wavelength and the energy to or from one or both the aerials is passed through an amplitude control arrangement and one or both the feeders includes a phase adjuster so that the angular position of the lobes of the directional diagram may be varied while the depth of the troughs between the lobes is variable by the amplitude control. In a wireless receiver the phase adjusting means are preferably so operated that a source of interference lies in the direction of minimum reception. Phase adjustment is preferably effected by inserting selected lengths of conductor 11, 12, 13, Fig. 3, in one of the feeders while fine phase adjustment is effected by a tuned circuit 14 at a point A one quarter wavelength removed from the point B at which the receiver is connected. Amplitude control is effected by variable resistance 15, a change-over switch enabling the resistance to be placed in the line having the stronger signal. In a modification, Fig. 4 (not shown), fine phase adjustment is effected by gang controlled tuned'circuits one quarter wavelength apart, one having a resistance in series equal to the characteristic impedance of the feeder. In this arrangement amplitude adjustment is similarly effected by ganged spaced resistances one of which is in series with a resistance equal to the characteristic impedance of the line and the coarse phase adjustment is effected by connecting the receiver to a tapping switch associated with a conductor one half wavelength long which terminates the lines. In other arrangements a variable length of feeder of length equal to one wavelength and terminated by a.resistance may be included in one of the lines for coarse phase adjustment, Fig. 5 (not shown) and a variable coupling transformer may be used to adjust amplitude, Fig. 6 (not shown). In the latter arrangement the ratio of the mutual inductances may be varied by switching in more or less turns on the secondary coil. Fig. 7 shows a construction of variable coupling transformer in which the primary coils L1, L2 are formed by a cruciform copper sheet bent to form a box-like structure with the coupling coil L3 of strip copper on a hollow shaft. Alternatively amplitude control may be effected by a tapped half wavelength line, Fig. 9, with the mid-point connected to the common channel T. Specification 433,843 is referred to. Reference has been directed by the Comptroller to Specification 492,455.