GPS modernization will expand the area of positioning service and will increase its convenience. Particularly, the third civil frequency namely L5, which will be provided by both modernized GPS and QZSS, is expected to improve the performance of precise positioning using carrier phase observation. This paper reports an experimental result regarding the convenience of additional L5 signal. Actual navigation signals generated from GPS simulator were received by triple frequency GPS receiver in the experiment. Navigation data, pseudo-range and carrier phase observation have been obtained and used for the analysis. This experiment verifies the improvement of ambiguity fixing time and multi-path mitigation using three frequency signals.