Over on YouTube SignalsEverywhere has just uploaded his latest video about using a HackRF and Airspy R2/Mini to explore the signals coming out of an internet cable modem's coax cable. In the video he performs a wideband scan with his Airspy R2 and the SpectrumSpy software which shows not only his, but the downstream signals from other users in his neighborhood on the cable network too.
Next using his HackRF with Spectrum Analyzer and the hackrf_sweep fast sweeping software, he was able to determine the uplink portion of his cable modem. By running an internet speed test in the background he was also able to visualize the increased cable data activity on the spectrum waterfall display.
The Secret Signals Hiding In Your Cable Modem | SDR Used to Sniff Cable Internet Modem Coax