Designs and Efficiencies of Large Air Core Inductances

Representative designs of large air core antenna tuning inductances are described, in types suitable for outdoor and indoor service. The latest improved designs are described in greater detail and compared with earlier designs on a basis of efficiency and kilovolt-ampere capacity. Formulas are given for calculating the ohmic and eddy current conductor power factor of coils using finely stranded, separately-insulated strands. In graphical form are shown the variations of ohmic and eddy current power factor with frequency, with four different conductors wound in a given arrangement to given dimensions; also the variation of the sum of ohmic and eddy current power factors with frequencies for a representative conductor on various diameters. These values were calculated by the formulas given, and indicate very high efficiencies for the latest types of coils.