The frequency dependence of the dielectric permittivity's maximum has been studied for poled and unpoled doped relaxor strontium barium niobate Sr0.61Ba0.39Nb2O6:Cr3 + (SBN-61:Cr). In both cases the maximum found is broad and the frequency dispersion is strong. The present view of random fields compensation in the unpoled sample is not suitable for explaining this experimental result. We propose a new mechanism where the dispersion of quenched random electric fields, affecting the nanodomains, is minimized after poling. We test our proposal by numerical simulations on a random field Ising model. Results obtained are in agreement with the polarization's measurements presented by Granzow et al. (Phys. Rev. Lett. 92 (2004) 065701).