Radio uses of powdered-iron cores

THE use of finely divided particles of magnetic material pressed into shape and held together with a suitable bonding material has been employed for electrical purposes for at least half a century. The improvements in manufacturing technique, the lowering of costs, and the ability to produce materials having relatively high permeability and comparatively low losses, for frequencies even as high as 100 megacycles, have resulted in a substantial use of powdered core materials for communications circuits.