Simple preconditioning technique: Empirical formula for condition number reduction at a junction of several wires

The condition number for a method-of-moments´ impedance matrix resulting from a junction of several wires is frequency dependant and can be minimized at a given frequency using several approaches. An empirical formula for an optimum, condition-number minimizing selection of the dependent variable for a multiplet on the junction is presented. The results indicate possibility to lower the condition number by an order of magnitude with virtually no computational overhead. The results may also be used to mesh the structure so as to minimize the condition number.