For any brand new ECH system on DIII-D, it is prudent to experimentally verify that the polarizers are correctly set. The O-mode absorption is strongly Te dependent, the difference from X-mode could be 5 times lower. ECH absorption/deposition measurements will be made using calculated pure X-mode and pure O-mode.We will also use different Bt values where the relative X-mode and O-mode power deposition peak locations switch. To verify the optimal polarizer settings for X-mode, the calculated O-mode fraction will be scanned shot-to-shot by varying the inclination at fixed ellipticity, or by scanning the ellipticity at fixed inclination. The power deposition profile can be determined by modulating the gyrotron power and fitting the measured electron temperature oscillations to the Fourier-transformed first-order energy conservation equation. At high frequency limit, absorbed power can be extracted form the responding electron temperature measured by ECE. Modulated ECH via top launch will be applied at different Bt to obtain deposition measurements. Three repeat shots (same ne and Te profiles) with constant EC power will be taken that vary between top launch co-ECCD, outside launch co-ECCD and outside launch radial ECH with the same deposition location for the ECCD part.