A mixed-domain oscilloscope (MDO) includes a signal generator configured to generate a test signal having a span ranging from a user-configurable start frequency to a user configurable stop frequency, an output channel coupled to the signal generator and configured to transmit the test signal, an RF input channel configured to receive a return signal based on the test signal, an acquisition section configured to acquire and digitize the return signal as an acquisition record, and a ramp busy signal generator configured to substantially time-align the acquisition record with the test signal. The test signal includes a chirp signal that is a linearly swept sine wave that spans between the user-configurable start frequency and the user-configurable stop frequency. Methods include calibrating the chirp signal, connecting the MDO in various test configurations relative to external return loss bridge and DUT equipment, and performing measurements such as S21 (db), S11 (db), and distance-to-fault type measurements.