Fig 1.1 illustrates the electric and magnetic field patterns for the mode used in the rectangular waveguides of the MWT530 experiments. This mode is called TE1.0 mode. The figures indicate that the electric field is unidirectional,and there is no transverse magnetic field. Other modes have different number suffixes indicating the number of changes of field direction which occur in each transverse direction. A special mode called TEM has both electric and magnetic fields perpendicular to the direction of propagation. This mode of propagation occurs in free space and in coaaxial lines.