Balanced measurements to very high frequencies are becoming more and more commonplace. Twisted pair cables are expected to pass digital data with frequency content as high as 18 GHz or more. SRDES lanes on printed circuit boards may require bandwidths just as high. High-speed differential amplifiers are needed to drive ADCs and must be properly evaluated. It is possible to compute balanced differential measurements from a series of unbalanced measurements for passive media, such as cables, but this requires a four port VNA. Differential amplifiers require a real differential drive that can only be provided by a balun. In this video, we will demonstrate how to use a VNA to make high frequency balun measurements with a CMT VNA.