A printed dipole antenna loading a diode as an IM source is proposed in this report. It is shown thatIM generated from the printed antenna is suppressed by using a semi-rigid coaxial cable as feeding line. The effectivenessof a loop-loaded diode is also confirmed as an external IM-source of antennas. Using the proposed antennain comparison with the IM-source loaded patch antenna, the effect of an antenna gain on the measurement of anexternal IM source is evaluated by experiment. The results indicates that it is possible to characterize externalIM-sources uniquely by using its net excitation power.