An integrated quasioptical receiver consisting of a planar double dipole antenna, SIS mixer and a superconducting local oscillator with matching circuits has been designed, fabricated and tested. A Flux-Flow Oscillator (FFO) based on unidirectional viscous flow of magnetic vortices in a long Josephson tunnel junction is employed as a local oscillator. All components of the receiver are integrated on a 4 mm x 4 mm x 0.2 mm crystalline quartz substrate on a base of the same Nb-AlOx-Nb trilayer in one technological run. The receiver has been studied in the frequency range 360 - 490 GHz. A lowest DSB noise temperature of 470 - 560 K has been achieved within the frequency range 425 - 455 GHz. Test circuits each comprising a FFO and a SIS detector have been experimentally investigated at frequencies up to 850 GHz. A new reliable technique for measuring the spectral linewidth of the integrated oscillators has been developed; the possibility of frequency locking of a FFO to an external microwave source has been demonstrated. The spectral linewidth of a FFO has been measured in the frequency range 250 - 580 GHz; a linewidth as low as 200 kHz is obtained at 450 GHz.