A test and measurement instrument including a signal generator configured to generate a waveform to be sent over a cable to a device under test (DUT) and a real-time waveform monitor (RTWM) circuit. The RTWM is configured to determine a propagation delay of the cable, capture a first waveform, including an incident waveform and a reflection waveform at a first test point between the signal generator and the DUT, capture a second waveform including at least the incident waveform at a second test point between the signal generator and the DUT, determine a reflection waveform and the incident waveform based on the first waveform and the second waveform, and determine a DUT waveform based on the incident waveform, the reflection waveform, and the propagation delay. The DUT waveform represents the waveform generated by the signal generator as received by the DUT.