Fig. 4. Automatic network analyzer (ANA) results collected for a sand saturated with a 10-dS m^–1 NaCl solution. (a) Relative amplitude as a function of frequency. The dashed line represents the minimum amplitude for reliable measurements based on the manufacturer's reported feed-through cutoff. (b) Linearized phase as a function of frequency for the 10-dS m^–1 and air cases and the difference between these two measurements.