Larry, AE5CZ, sent me files from a DeepVNA 101 attached to a 12" ground probe. The first three plots are with the probe rods in air. You do this to determine the compensation for the capacitance between rods due to probe dielectric. The dim region of the S11 curves is where |S11| > 1 and extends to 18 MHz. Note the effect on calculated resistance, which is the real part of 50(1+S11)/(1-S11). Measurement noise is minimal. This issue did not seem to affect ground measurements, shown in the last plot. They show no artifacts or noise, and are what you might expect from New Mexico ground.
Brian
