The search for radio signals from technologically advanced extraterrestrial intelligence has traditionally focused around 1.4 GHz. In this paper, we extend the exploration into previously uncharted frequency space, presenting extensive observations at 6 GHz and pioneering the first survey at 18 GHz with the Sardinia Radio Telescope (SRT). Our strategy entailed rigorous observation sessions, totaling 73 h, directed towards the Galactic Center and 72 selected TESS targets—making this the most comprehensive high-frequency technosignature search to date. Our narrowband signal search found no definitive evidence of drifting signals that could suggest an extraterrestrial origin from the surveyed regions. Nevertheless, our efforts have enabled us to set new constraints on the presence of radio emissions from approximately 5 × 105 stars, establishing an isotropic radiated power limit of 1.8 × 1019 W. We also provide a comparative analysis of the ’hits’ recorded across both frequencies to highlight the significance of pursuing technosignature searches at higher frequencies, where the spectral landscape is less congested and more conducive to detection.

Published in: Acta Astronautica, Volume 233, pp. 155-167 (2025)