Nonlinear interactions dipolar, dipole-exchange, and purely exchange spin waves be tween themselves and with high-frequency electromagnetic pumping were studied experi mentally in Permalloy (NiFe) metallic films.The main characteristic feature of spin waves in metallic films (in contrast with similar waves in dielectric ferrite films) is their large dissipation, which results in rather small values of mean free path not exceeding several tens of microns.The method of parallel pumping of spin wave instability by external electromagnetic signal was used to compensate dissipation and increase mean free path of excited spin waves.It was found that at large (supercritical) values of the pumping power electromagnetic radiation at the half pumping frequency can be registered in a Permalloy film, and two independent mechanisms of such radiation were suggested and experimentally confirmed.