We present the results of a pilot observation testing the performance of Frequency Phase Transfer (FPT) and Source/Frequency Phase Referencing (SFPR) at 22 and 43 GHz using the Korean VLBI Network (KVN) and the Yebes-40m telescope in Spain, with a baseline length of $\sim$9,000 km. The ultimate goal of this project is to monitor the orbital motion of supermassive black hole binaries (SMBHBs) using high-precision VLBI astrometry, which requires a precision of a few micro-arcseconds. We find that the FPTed visibility phase at 43 GHz on Yebes-KVN baselines shows a significant improvement in coherence time compared to the non-FPT phase, demonstrating that FPT is effective even with long baselines. We also present preliminary SFPR maps showing the feasibility of high astrometric precision within 10 μas. We discuss remaining issues, such as the time evolution of residual phases at long baselines, and outline future observation plans for long baseline SFPR, including multi-frequency antennas up to 86 GHz.