The 8971C noise figure test set allows the 8970B to make noise figure measurements over an extended frequency range. Careful design and high-performance components, including a stable YIG filter, allow broadband single-sideband measurements from 10 MHz to 26.5 GHz with a single calibration and sweep. A low-noise preamplifier built into the noise figure test set lowers the second-stage noise figure, thereby reducing a major source of measurement uncertainty. Measurement modes in the 8970B allow for double down-conversion using the 8971C as the second downconverter.