  We analyzed the presently available experimental data on nucleon
electromagnetic form factors within a multipole model based on dispersion
relations. A good fit of the data is achieved by considering the coefficients
of the multipole expansions as logarithmic functions of the momentum transfer
squared. The superconvergence relations, applied to this coefficients, makes
the model agree with unitary constraints and pQCD asymptotics for the Dirac and
Pauli form factors. The soft photon emission is proposed as a mechanism
responsible for the difference between the Rosenbluth, polarization and
beam--target--asymmetry data. It is shown, that the experimentally measured
cross sections depend not only on the Dirac and Pauli form factors, but also on
the average number of the photons emitted. For proton this number is shown to
be different for different types of experimental measurements and then
estimated phenomenologically. For neutron the same mechanism predicts, that the
data form different types of experiments must coincide with high accuracy. A
joint fit of all the experimental data reproduce the $Q^2-$dependence with the
accuracy $\chi^2/dof=0.86$. Predictions of the model, that 1) the ratios of the
proton form factors $G_E/G_M$ are different for Rosenbluth, polarization and
beam--target--asymmetry experiments and 2) similar ratios are nearly the same
for neutron, can be used for experimental verification of the model.
