A heterodyne receiver scheme based on electro-optical (EO) downconversion is introduced. The local oscillator (LO) and the retrieved intermediate frequency (IF) signals are remotely distributed over fiber to/from a single ultra-nonlinear semiconductor optical amplifier (SOA) device that acts as a highly nonlinear mixer device, enhancing the downconversion performance of the system. The photonic LO is generated modulating a DFB under gain switching (GS), eliminating the need of external elements and the polarization dependency. We evaluate the performance of the downconversion up to frequencies much higher than the bandwidth of the devices (15 GHz). Results show broadband heterodyne detection performance of the system. The presented scheme offers advantages in terms of compactness and cost efficiency and can be easily scaled to remotely reach multiple receivers in scalable detection arrays.