Low loss current and voltage probes are integrated in parallel plate airlines (slablines) to be used either as separate modules inserted between tuner and DUT in load pull test setups, or integrated in the impedance tuners themselves. The probes are inserted orthogonally at exactly the same reference plane relative to the DUT, maximizing bandwidth and the minimizing deformation of the detected electric and magnetic fields. The probes are used to detect the actual voltage and current waveforms and feed into an amplitude-and-phase calibrated high speed oscilloscope, including several harmonic frequencies. The actual real time voltage and current time domain waves are transformed into the frequency domain using fast Fourier transformation (FFT), de-embedded to the DUT reference plane and inverse transformed into the time domain using inverse Fourier transformation (FFT−1). The result of this real-time operation is the actual dynamic load line of the DUT at its terminals.