1,222,518. Aerials. L. T. V. ELECTROSYSTEMS Inc. 8 Feb., 1968, No. 6261/68. Heading H4A. Signals from receptors providing broad beam reception patterns inclined in relation to one another are combined to produce two signals having dissimilar virtual reception patterns, one of which has a substantially zero portion over a narrow angle. The other of the said two signals is attenuated outside said narrow angle, so that an equivalent narrow beam reception pattern is obtained from it. In a first embodiment, signals from an omnidirectional whip aerial A4, Fig. 4, are combined with signals from one loop of a rotatable crossedloop aerial 10 in an adder 20, so that signals conforming to an equivalent cardioid directional pattern E CN are obtained as output which are fed to one input of a correlator 30. The signals from the other loop of the crossed-loop aerial 10 are fed to the other input of the correlator 30, which only gives output when both its inputs are of the same phase. A half-cardioid type directional pattern E H results, having half of a narrow beam along the null line of the cardioid E CN . Signals from the said other loop are also fed through a phase inverter 50 to one input of a correlator 40, whose other input is fed by output from the correlator 30. A narrow beam equivalent directional diagram P r4 is thus obtained. In a second embodiment (Fig. 3, not shown) a single rotatable loop aerial is used in conjunction with a whip aerial. Signals from the latter are fed direct to one input of a correlator and also in combination with those from the loop aerial, and subsequent phase inversion, to the other input of said correlator, from which an output equivalent to that from a narrow beam aerial is obtained. In a third embodiment, which is an elaboration of the first embodiment, signals from the two loops of a fixed crossedloop aerial B5, Fig. 5, and from a whip aerial A5 are pre-amplified and are transmitted to a remote control chassis. The signals from the loops are fed via emitter follower amplifiers 4, 5 to the respective rectangularly disposed stator coils 8À1, 8À2 of a resolver 7. The rotor has two rectangularly disposed coils 9À1, 9À2, which give respective outputs corresponding to those from two separate loop aerials, i.e., with figure-ofeight directional patterns at 90 degrees to each other. Both outputs are taken through phase shifting integrating networks 11, 14, and that from the rotor coil 9À1 is fed to one input terminal of an adder 20. The amplified whip aerial signal is fed through a differentiator 12 to the other input terminal of the adder 20, the output from which corresponds to a cardioid directional pattern, and which after passing through a tuned circuit 22, an emitter follower circuit 24, an optional interference rejection circuit 70, a gain control 26, and an amplifier 28, is taken to respective input terminals d1 and d of a correlator 30 and of a selector switch 60. Output from the network 14, which is fed from the other rotor coil 9À2 of the resolver 7, is taken through an additional amplifier 21, a tuned circuit 23, an emitter follower circuit 25, a gain control 27, and an amplifier 29 to an input terminal c1 of the correlator 30, and through a phase inverting circuit 50 to one input terminal of a correlator 40. The output from the correlator 30, corresponding to a half-cardioid directional pattern, is taken through a correction circuit 51 to the other input of the correlator 40. Output from the latter, corresponding to a narrow beam directional pattern, is taken to an input terminal of the selector switch 60, by means of which it may be coupled through an output driver 61 for utilization. The switch 60 also allows the choice as alternative outputs of signals originating in either rotor coil of the resolver 7, or originating in both coils and combined in an adder 15, or originating in the whip aerial A5. In a fourth embodiment (Fig. 13, not shown), signals from a single rotatable loop aerial are combined with those from a whip aerial in two adders, the input from the whip aerial being phase inverted in one case. The outputs from the adders are fed to a correlator, whose output then corresponds to a narrow beam directional pattern. Ganged tunable tracking filters may be inserted in the output lines from the adders and the correlator. In a fifth embodiment (Fig. 14, not shown) signals from a crossed-loop aerial are fed to a resolver (which is similar to the resolver 7, Fig. 5) outputs from which are added and are fed to one input terminal of a first correlator. A signal from a whip aerial is fed to the other input terminal of said first correlator, which provides an output corresponding to a cardioid patterned directional signal. Said output signal is phase reversed, and is then fed to one input terminal of a second correlator, which has as second input the signal from the whip aerial. The output of the second correlator corresponds to a narrow beam directional pattern. In a sixth embodiment (Fig. 15, not shown), also using a crossed-loop aerial with resolver and a whip aerial, signals from one rotor coil of the resolver are combined in an adder with those from the whip aerial to produce signals corresponding to a cardioid directional pattern, which are fed to two correlators and to a first inverter. Signals from the other rotor coil of the resolver are fed directly to the input of one correlator, and through a second inverter to the other input of the other correlator. The outputs of the correlators correspond to halfcardioid directional patterns of opposite hands, and these are combined in an adder to give an output corresponding to a pear-shaped directional pattern, which is then combined in a final adder with the output from said first inverter to give an output corresponding to a narrow beam directional pattern. Correlating means are described in which one signal is fed to the primary of a transformer (T), Fig. 7 (not shown), which has a centre-tapped secondary connected to opposite junctions (J1), (J2) of a bridge comprising four diodes (D1), (D2), (D3), (D4). The other signal is connected between the centre point of the secondary of the transformer (T) and earth, and output is taken from a point (m) which is connected to the other opposite junctions (J3), (J4) of said bridge by diodes (D5), (D6), respectively (see Specification 1,222,519). An interference rejection circuit 70, Fig. 5, may comprise an adder placed in circuit between the emitterfollower circuit 24 and the gain control 26, and having a second input from the slider of a potentiometer which is connected across the inverter 50, said potentiometer having an earthed centre-point. In this way, the cardioid directional pattern to which the signals at the terminal d1 of the correlator 30 correspond, may be effectively rotated (Fig. 11, not shown). In a preferred arrangement, output from the amplifier 29, Fig. 5, is connected to a potentiometer via a para-phase amplifier and cathode follower stages (Fig. 12, not shown). (See Specification 1,222,520).