The question of time vs. frequency, as the most useful measurement domain, has long been a controversial topic. In some cases, it leads to rather heated discussions. The argument in favor of a vector network analyzer (VNA), a frequency domain instrument, is that the dynamic range and signal to noise ratio (SNR) of a VNA are much better than they are for a time domain reflectometer (TDR). The argument in favor of TDR measurements is that they tend to be lower cost and are taken from a direct reading, so there is little to interpret. Fortunately, most new TDRs can also transform measurements to S-parameters (much like a VNA) and most new VNAs can also transform to time (providing TDR equivalent data).
Having said all of this, the measurement of a PCB plane using a VNA may not be as straightforward as you might expect. One simple trick makes it easy. Read more: