Permeability of magnetic materials tested by high-frequency calibration

The National Bureau of Standards (NBS) recently established a calibration service for determining the radio-frequency permeability and loss factor of magnetic materials in the frequency range between 50 kc and 30 megacycles. The primary calibrating standard is a coaxial line of variable length constructed to dimensions of extremely high accuracy. The characteristics of magnetic materials, such as the ferrites and powdered irons, are determined in terms of the variation in the length of the line. The Bureau also has developed a secondary standard of calibration that may be simply reproduced and utilized in the manufacture of magnetic materials.