The VNA has evolved from a basic power detector to a complex test system for precision modulation measurements in sub-THz frequencies. Significant instrument refinement over the past fifty years including modern software implementations in the VNA such as digital signal processing (DSP), extensive storage, fast Fourier transform (FFT) applied to the massive data captured, coherent acquisition strategies, digital predistortion (DPD) correction, precision VNA calibration techniques, and external apparatus such as digital to analog converters (DACs), external wideband mixers, vector-component analyzer (VCA) and VNA extenders all combine to enable high precision measurements of modulated signals in sub-THz frequencies necessary for 6G application research and development. The VNA may well be the most precise way to measure these signals today.