Abstract
Gyromagnetic loading of waveguide structures curiously modifies the conventional modal description of propagation. Among the anomalies produced is that in which propagation is found to occur in vanishingly small waveguide cross sections at a given frequency. Another is the appearance of spurnous resonances in an ostensibly single mode waveguide. A physical basis of such phenomena is described employing the birefringent character of the gyromagnetic medium, and corroborating experimental evidence is offered.