RF interference is a big and growing issue with drones. Since we have so many RF devices onboard -- RC, telemetry, wireless video, GPS, to say nothings of accidental RF radiators such PCBs and wiring -- avoiding interference has become something of a necessary black art. The RF Explorer can help. It's open source hardware available from Seeed Studios for as little as $99.
They have a good interview with the creator, Ariel Rocholl, here. Some excerpts:
Interestingly, RF Explorer was born as a diagnose tool for Radio Control airplane pilots. Since a few years now, the RC world is on a big revolution due to all the improvements done in drones, FPV, 2.4GHz spectrum radio link, video links, etc. There is plenty of technology there, in some cases really outstanding achievements.
But something was missing: there were simply no way for a pilot that put $2000 equipment on an RC plane to observe the RF spectrum and detect potential collisions or interferences, most just flied the plane till it started to get control or video link problems, in the hope that not being too late or too far to get it back under control. RF Explorer changed that for good: most pilots just do a careful inspection of the spectrum on different frequencies at the flying field now, as well as the internal plane setup, to proactively detect problems before they put in risk the expensive equipment on board. In many cases, RF Explorer helped to finetune the internal plane in a way that electronics radiate less interference and so the plane get farther distances safer.