This paper intends to study the effect of variations of aspect ratio (the ratio of outer radius to inner radius of conductor) and frequency to the normalized admittance (normalized conductance and susceptance) of oil palm fruit with various moisture content (MC) on performance of RG405/U semi-rigid cable (open-ended coaxial line). Both finite difference method (FDM) and quasi-static model (admittance model) were used to compare response of normalised conductance and susceptance due to 30%, 40%, 60%, 70% and 80% of moisture content that explain all ripeness stage of oil palm fruit. Finite difference method is used to simulate complex admittance due to different MC in oil palm fruit in various ripeness. The FDM results were then compared with the quasi-static model through error analysis. The aspect ratio of 3.298 has smaller error of normalized conductance when frequency range <3 GHz.