Calculation technique for obtaining secondary emission characteristics (SEC) of a resonant perfectly conducting objects in free space is considered. Developed technique is based on the magnetic field integral equation (IE) solving. For determination of applicability domain of algorithm developed by authors scattering characteristics calculated for simple objects (sphere, ellipsoid, cylinder, disk, and cube) are compared with experimental data, and also with results obtained using other numerical methods. Features of calculation of the considered object SEC (including ultrawideband pulse responses) are discussed. Data obtained for model scatterers allow to determine parameters of numerical algorithm for calculation SEC of complex shape objects.