Attenuation in nickel and mild-steel waveguides at 9375 Mc/s

Measurements of the attenuations produced by air-filled waveguides of nickel and mild steel have been made at a frequency of 9 375 Mc/s. It is shown that the permeability of a ferromagnetic material can be determined from such measurements provided the roughness of the waveguide internal surfaces can be estimated with reasonable certainty. It is found that mild-steel waveguides with machined internal surfaces give attenuations as high as 3.79 db/m, and the figure of 3 is deduced for the permeability of commercially-pure-nickel drawn waveguide.