An onboard device for receiving a signal coming from an aircraft at a distance d from the device, said signal resulting from the combination of multiple propagation paths, one of the paths corresponding to the main echo of the transmitted signal, said device including an equalizer of processing depth T. The device includes means for estimating the distance covered by the second path, means for deducing therefrom a delay value τ associated with it, means for estimating when τ is greater than or equal to T the interfering signal associated with the main echo and for reducing the contribution of said signal to the total level of interference received. Also a system of communication between aircraft using the onboard device.