Practical implementations of electromagnetic interference source localization, including transient events such as electrostatic discharges, have a wide range of industrial applications. We show the experimental localization of both timeharmonic and transient sources using low-cost measurement equipment, including a software-defined radio for GHz-range time-domain measurements, combined with the time-reversal method. The backpropagation stage of time reversal is achieved using experimental data, eliminating the need for a computational model of the device under test.