A reed relay designed to carry high frequencies will generally use a coaxial design approach. With this in mind the formula to calculate the characteristic impedance is the following: Z = 60/(√(€R) + ln(2h/d)) where Z is the characteristic impedance, √ is the square root, (€R) is the dielectric constant between the shield and the reed switch, ln – is the natural log, h is diameter of the shield, d is the diameter of the reed switch.
