Frequency down-conversion of a received signal in an integrated receiver with a superconducting heterodyne oscillator is simulated. The effect of the nonideal heterodyne spectrum on the transformation is assessed. The possibility of elimination of distortions introduced by the heterodyne in the course of the input spectrum reconstruction is investigated. A new method for signal spectrum reconstruction is proposed and studied. The effect of noise at the receiver output on the reconstructed spectrum of the original signal is studied. The requirements for the heterodyne spectral parameters providing for the necessary accuracy of reconstruction are determined.