  This paper presents a thorough investigation into nonradiating sources of
Maxwell's equations. Various characterizations are developed to clarify the
properties of nonradiating sources, considering their varying degrees of
regularity. Furthermore, the characterizations are examined on far-field
patterns and near-field data of the electric field, along with the null spaces
of integral operators. The study includes the explicit construction of several
illustrative examples to demonstrate the presence of nonradiating sources in
different null spaces.
