OSMOCOM-fft

Dear all, I am confused about some parameters of osmocom fft spectrum analyzer. I am wonder what exactly the vertical axis shows? It is written Power(dB); if so, what is the reference power? Is it 1dBW? Moreover, by changing the PGA Gain, I will have different values of power (dB). What is the relation between PGA gain and the received power in dBm? In general, does anyone know how should I find the received power in dBm, having the PGA gain(dB) and the value on vertical axis. (Picture in attach) Looking forward to your reply. Bests, -- -- Le informazioni contenute nella presente comunicazione sono di natura  privata e come tali sono da considerarsi riservate ed indirizzate  esclusivamente ai destinatari indicati e per le finalità strettamente  legate al relativo contenuto. Se avete ricevuto questo messaggio per  errore, vi preghiamo di eliminarlo e di inviare una comunicazione  all’indirizzo e-mail del mittente. -- The information transmitted is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. If you received this in error, please contact the sender and delete the material.