-This contribution aims at the experimental confirmation of the advantages of the harmonic manipulation theory, using a low-frequency low-cost characterization setup. A 0.5-µm 10x100-µm (1-mm gate periphery) GaN HEMT has been characterized synthesizing at the current-generator plane different load conditions, realizing tuned-load and Class-F operation. The measurements clearly demonstrate the importance of by synthesizing the required loads at the correct reference plane, giving an experimental proof of the performance predicted by theoretical analysis.Index Terms -FET, harmonic manipulation, integrated circuit measurements, microwave power amplifier, semiconductor device measurements.