A high-frequency VNA system is provided using non-linear transmission line (NLTL or shockline) based samplers configured to provide scalable operation characteristics. Scaling to adjust noise performance vs. frequency is accomplished as follows: (1) increasing or decreasing the fall time of a shockline's output voltage waveform. This is accomplished by changing the number of Schottky varactors in a shockline, as well as changing the shockline's Bragg cutoff frequency by setting the spacing between Schottky varactors; (2) changing the structure of the pulse-forming network connected with the sampler by changing the length of the differentiator arms in the sampler pulse-forming network; and (3) changing the LO signal frequency applied to the shockline. Multiple NLTL based samplers are multiplexed to form a broadband reflectometer with the multiplexing circuitry selectively connecting one of the NLTL based sampler segments at a time to allow user selection of a desired performance vs. frequency response for each segment.