Abstract:It needs to reduce the daily variation (diurnal) in the twoway satellite time and frequency transfer (TWSTFT) and explore the reasons. Using the redundancy of the current AsiaEurope international twoway time comparison network via ABS2A satellite, TWSTFT links of different baseline lengths at different periods are selected. Firstly, the satellite time and ranging equipment (SATRE) TWSTFT results with the softwaredefined radio (SDR) receivers TWSTFT results are compared. Then, with different laboratories in Asia and Europe as a relaying laboratory, the results of SATRE TWSTFT direct and indirect links are compared. Finally, the GPS precise point positioning (PPP) time comparison, which is independent of TWSTFT, is used as a reference to evaluate the performance of the aforementioned results. Experimental results show that the average gain factor of SDR TWSTFT for AsiaEurope and Asia SATRE TWSTFT time deviation (TDEV) is around 175. For the baseline of National Time Service Center (NTSC) and National Institute of Metrology (NIM), the gain factor of TDEV is 122 for the indirect link via PhysikalischTechnische Bundesanstalt (PTB).