485,682. Directive wireless signalling. STANDARD TELEPHONES & CABLES, Ltd. Jan. 1, 1937, No. 75. Convention date, Jan. 11, 1936. [Class 40 (v)] Directive aerials of the V-shaped or rhombic type described in Specifications 353,517 and 392,201, are adapted to receive waves of different frequency, within a given band, and arriving from different directions. The aerial is characterized by the following features ; (a) the length L of each limb 13 .. 16 in Fig. 1, is greater than twice the working wavelength ; (b) is equal to its projection on the vertical plane of propagation plus one-half the working wavelength ; (c) is at least five times greater than its height H above ground. The aerial is made uni-directive by the resistances 12a, 12b, 12c, the broken lines showing how the interior angles are adjusted to favour signals coming from different vertical directions at different wavelengths. Fig. 2 shows three rhombic aerials 8, 9, 10, each arranged to receive different wavelengths. The aerials are connected by separate transmission lines 11 to a receiver or transmitter 3. Fig. 5 shows an end - on arrangement in which each aerial comprises two receiving elements 30 and two counterpoise elements 31, the whole being mounted on grooved guides 32, 33 so that it can be telescoped, as shown in dotted lines to receive waves of different frequency. Two rhombic aerials may be set at right - angles, one to receive the vertical and the other the horizontal component of an incoming wave, the two aerials being linked to a common circuit through separate amplifiers fitted with automatic volume control to minimize fading, Fig. 6 (not shown). Fig. 7 shows a universallyadjustable aerial, which may be used to determine the " arrival angles " of waves of different frequency, in order to facilitate the setting of the aerial shown in Fig. 1. Each aerial may be associated with a suitably-spaced " TWIN "which acts as a reflector and replaces the dissipating resistances 12 in Fig. 1. Fig. 14 shows a three-dimensional array of horizontal rhombic aerials 78, arranged in bays, rows, and tiers, each one of which may be used independently, though the combination gives superior directional results. The Specification as open to inspection under Sect. 91 also describes rhombic aerial arrays arranged vertically instead of horizontally, and extending in one, two, or three dimensions. This subject-matter does not appear in the Specification as accepted.
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