Photo of a RTL-SDR receiver stick testing a Mini-Circuits low pass RF filter with a Pluto SDR as a transmit source.

Screen capture of SATSAGEN running on the Ham Win11 PC, with the software controlling the RTL-SDR receiver and Pluto SDR transmit source. A frequency sweep is running from 70 to 1200 MHz. The plot shows the reference line at 0 dB and the classic low-pass filter shape below that the Mini-Circuits SLP-300 filter provides (attenuating frequencies above the pass band up to 300 MHz).