This article describes the manner in which an experimental investigation of the effect of transponder pre-equalization in direct broadcast satellite (DBS) transmission has been carried out. Resulting differential gain (DG) and differential phase (DP) have been measured both with and without the transponder equalizer in the up-path chain for different combinations of the earth station high-power amplifier (HPA)/transponder traveling wave tube amplifier (TWTA) input backoff (operating level below single-carrier saturated level) using NTSC signal format. The video carrier used was first located in the transponder band center, and later shifted by 4 MHz from the band center. Detailed analyses are given in the Appendix.