In a previous work, we introduced a spectrum sharing technique called Vandermonde-subspace frequency division multiplexing (VFDM). This overlay technique allows the coexistence of a downlink orthogonal frequency division multiplexing (OFDM) macro-cell and a cognitive small-cell in a time division duplex mode. In that work, VFDM was shown to be able to completely cancel the interference towards a primary macro-cell system at the price of perfect channel state information (CSI) at the opportunistic secondary small-cell. In this work, we propose a prototype of VFDM transceiver as a first step towards a proof of concept of the complete technique. We focus on the secondary small-cell and, using the new SDR4All platform developed at the Large Networks and Systems Group (LANEAS) (SUPELEC), we design the transmitter/receiver pair needed for our test. The obtained results are promising and show the practical feasibility of a VFDM transmission over a secondary link.