Computational and measured results of the phase and amplitude distributions of the fields radiated by four circular sources are presented. The limitations of the results are discussed, indicating that meaningful comparison is possible only for planes in and beyond the near‐ and farfield transition regions. The inclusion of an effective radius into the theoretical calculations of a piston in a rigid baffle gives generally good agreement between experiment and theory. The inclusion of the finite size of the receiver produces an additional small improvement. The phase distributions are clearly seen to be a more sensitive index of the field structure than the amplitude distributions commonly used. The value of the work is in suggesting conditions under which one or two amplitude measurements in the field may be used to define effective parameters for an ideal theoretical computation which bears a close resemblance to the actual field radiated by an (imperfect) probe.