In this work we present the comparison of group delays obtained by RASFX and DiFX correlators using different post-processing software.
We found that the difference of the group delays from both correlators are mainly due to the different mathematical implementation
of the correlation and post-processing algorithms.
The data converter software have been developed which allows to use PIMA post-processing routine on RASFX correlator data instead of the native RASFX post-processing software WOPS. A series of intensive VLBI sessions were processed using this new approach.