In this paper, we report the preliminary results of an Engineering Model of a complete SSPA, developed for Galileo satellite system (E1 band, 1575.42 MHz), and based on UMS GaN (GH50-10) technology. The SSPA includes also satellite interfaces (e.g., internal power supply generation unit, telemetry and telecommand functionalities) and measured results show an output power larger than the targeted 230W, with a PAE greater than 40%. Moreover, a very good stability in frequency was measured, with a gain ripple lower than 0.5 dB in 50MHz of bandwidth, and less than 0.2 dBpp in 10 MHz