A machine for calculating the polar diagram of an antenna system
01 January 1943
The machine described, which in its present form will calculate the polar diagram of systems with 2 to 5 aerials, makes use of "Selsyn" motors. These have 3-ph. stators and a 1-ph. rotor and use is made of the property that the phase of the rotor e.m.f. is exactly prop its angular position. The various rotors are restrained in angular positions which represent the phases of the received voltage components from the different aerials and by connecting the secondaries in series and measuring the total voltage with a high-impedance meter, the vector sum of all the secondary voltages is obtained. Examples of the practical application of the instrument are given. These include a solution of the inverse problem of determining the current and phase relationships which must exist in a system when a certain polar pattern is measured in the field.