In this paper the inverse source problem in presence of a reflecting plane is dealt with for a two-dimensional configuration and bounded rectilinear strip sources. The case of orthogonal (to a perfect electric conductor plane) source is considered. Analytical arguments are developed to estimate the singular value decomposition of the pertinent radiation operator. This allows to highlight the role played by the distance from the prefect electric conductor plane on the so-called number of degrees of freedom of the radiated field as well as on theachievable resolution while reconstructing the unknown sources.