A method of improving electrical isolation between a first circuit and a second circuit sharing a common substrate having an effective dielectric constant greater than that of air. The first and second circuits are spaced apart and separated from one another by an intermediate portion of the substrate. The method includes removing a portion of the intermediate portion to replace the portion removed with air thereby reducing the effective dielectric constant of the intermediate portion. By reducing the effective dielectric constant of the intermediate portion, electrical isolation between the first and second circuits is improved thereby reducing crosstalk between the first and second circuits. In particular implementations, the method may be used to reduce alien crosstalk between adjacent communication outlets in a patch panel.