The ubiquitous application of time domain reflectometry (TDR) in the measurement of water content in the soil sciences is inhibited in samples with high electrical conductivity (EC). TDR waveforms show a loss of signal amplitude in a saline (ionic) environment due to ohmic losses as described in the imaginary term of the complex dielectric permittivity. Recent studies have shown that coated TDR probes are successful in reducing the attenuation of TDR signal allowing the collection of waveforms and permittivity determination in solutions with EC as high as 70 dS m^-1. The objectives were: (i) to measure effective permittivities in highly saline solutions using coated probes and (ii) apply transmission line theory to a coaxial probe geometry for determination of solution permittivity. Variable coating thicknesses of a delrin heat-shrink on 20 cm coaxial probes were used to measure solution permittivities with electrical conductivities ranging from 0.02 – 150 dS m^-1. The model describes the effect of the coatings on the apparent dielectric permittivity measured. The true solution permittivity is derived from fitting model parameters to measured data. The application of the model parameterization lends itself to the use of coated probes for water content determination in saline soils.