The invention details specific electronic hardware and related firmware that allows signals to be sent from one platform and received electromagnetically by another, while detecting both phase and amplitude deviations at the receiver due to interactions with metallic bodies between or in the vicinity of the two platforms. Furthermore and most importantly, this is done with high phase precision without the physical presence of a reference signal, which is classically necessary for such phase measurements. This advance greatly increases coverage, versatility and sensitivity of EM techniques.