An electromagnetic tracking system includes a magnetic transmitter configured to output magnetic fields, a receiver responsive to the magnetic fields, an electronics assembly having conductive elements that cause distortion to the magnetic fields, and an output mechanism configured to output a position of the receiver relative to the magnetic transmitter, wherein the magnetic transmitter has at least one winding disposed around a hollow ferromagnetic core comprised of conductive material through which current is made to flow by the electronics, wherein the electronics assembly is at least partially contained within the hollow portion of the hollow ferromagnetic core. Methods of manufacturing include shaping walls into a hollow shell to surround an electronics assembly, covering the hollow shell with ferromagnetic material, inserting the wrapped hollow shell into a plastic bobbin, and winding the plastic bobbin with coil wire to produce three orthogonal windings.