SATGEN is a software that creates a spectrum analyzer or RF generator from a PC, which allows analyzing various RF circuits such as filters, amplifiers, bandpasses or analyzing the produced spectrum of the transmitter. Version 0.5 offers measurement via ADALM-PLUTO, HackRF One, simple spectrum analyzers, D6 JTGP-1033 and already cheap RTL-SDR receivers.
More details and SATGEN download https://www.albfer.com/en/2021/01/31/satsagen-0-5/