Abstract This paper presents a general and quasi‐analytical method aimed at reconstructing the electric field radiated by equipment under test (EUT), in free space through the knowledge of the values of the electric field sampled on the walls of a rectangular metallic enclosure. The algorithm is based on a set of equivalent magnetic and electric currents, regularly placed in a sub volume of the chamber, whose values are determined to reconstruct the electric field due to the EUT on the samples. Results show that the method is general because it can be applied to a wide set of EUTs, but it is also flexible because it is able to exploit some a priori knowledge of the source to improve its accuracy and efficiency