Long-wavelength response of magnetic reproducing heads

The distribution of the long-wavelength magnetic flux in unshielded and shielded magnetic head cores is described and calculated. Two effects are found, depending on the path of the flux: the "secondary gap effect" and the "undulation effect." The secondary gap effect causes an increasing output level at long wavelengths; it occurs because of the finite permeability of the core. The undulation effect causes undulation in the reproducing-head wavelength response; it depends primarily on the dimensions of the core in the neighborhood of the tape. Experimental measurements confirm the validity of the calculations quite well.