This paper proposes the frequency sharing or compatibility between Unmanned Aircraft System (UAS) and the Fixed Service (FS). The frequency sharing is the use of same frequency by different two systems. The frequency sharing or the compatibility between the two systems (UAS and FS) is modeled by the interference between those two systems. It is required to support the BLOS (Beyond Line of Sight) requirement in UAS. It's because the signal from the Unmanned Aircraft Control Station (UACS) has limitations in LOS (Line of Sight) condition. The BLOS spectrum is planned by utilizing the FSS (Fixed Satellite System) frequency band. It means that the UAS will use the satellite control over the BLOS condition. The main problem of the unmanned aircraft (UA) or unmanned aerial vehicle (UAV) deployment is the compatibility with the incumbent system. The allocation of FSS spectrum in the region 3 (Asia and Oceania Region) is in the band 12.2- 12.5 GHz. This frequency band is shared with the frequency of FS (Fixed Service). This paper calculates and simulates the scenario of interference. The scenario of interference is observed when the UAV (Unmanned Aerial Vehicle) or UA (Unmanned Aircraft) aviates above the area of FS. The simulation is conducted to investigate the interference from the FS emission into the UAV receiver. The results of simulation presents that the interference from the FS is not harmful to the UAV.