Short-wave directive transmitting and receiving aerials

The aerial systems used for short-wave communication between Madrid and Buenos Aires are described. For the transmitting aerial systems as many as sixteen vertical arrays, each comprising in effect three half-wave aerials, are arranged half a wave-length apart in the same plane, thus obtaining very marked directivity in a direction at right angles to the plane. The directive properties of the arrangement are further enhanced by the use of reflectors a quarter wave-length behind each unit, the reflectors being ordinarily parasitically driven by the radiating units. Special arrangements ensure that all the aerials are excited with currents in the same phase and of the same magnitude. For reception, zigzag aerials are employed. These consist of alternate horizontal and vertical portions, all of quarter wave-length, mounted on a wooden framework and having a total length equal to 5.5 lambda. An exactly similar reflector system is fixed a quarter wave-length behind the receiving aerial, and suitable arrangements for connecting the central points to the receiving station comprise a tuned circuit with connections to the receiving and reflecting aerials of length differing by a quarter wave-length in order that the voltages due to an incoming wave may produce additive effects. The transmission line connecting the aerial system to the receiving station is connected to two tapping points on the inductance of the tuned circuit.