The currents of two modes, normal mode and common mode flow along two-conductor lines placed in the air. We have so far developed the prediction method of common-mode current and radiation in a printed circuit board focusing on the imbalance of the transmission line. The difference of the imbalances causes the mode conversion, from normal mode to common mode. In this paper, it is examined that the vector sum of common-mode radiation and normal-mode radiation should be equal to total radiation. Each modal radiation is calculated separately with the corresponding equivalent model. The modeling method is applied to three kinds of printed-circuit-board structures. It is validated that the far electric field from the real-structure model agrees with the vector sum of far electric fields from normal-mode and common-mode equivalent models.