The deeper layers of the Venus atmosphere penetrated by the RF carrier signal transmitted by the VEX spacecraft during the atmospheric sounding can cause SNR degradations exceeding 50 dB along with frequency shifts and shift rates up to, respectively, 60 kHz and 2 kHz/s, depending on the observation geometry. Under such conditions, PLL-based receivers are soon driven in "out-of-lock" and data acquisition stops. Coherent sampling of the antenna voltage eliminates real-time tracking of the incoming signal, hence committing to proper digital post-processing techniques the possibility to recover...