The model explaining the phenomenon of a long-living radio-frequency echo-signal in superconductors according to which two ensembles of nonlinear oscillators take part in its formation has been offered. The first one is crystal lattices of grains of HTSC powder in which arise phonone fluctuations, and the second one is - fluxoid ensemble. Preservation of a phase of fluctuations by the second one allows to observe an echo-signal.