Paweł Spychalski's RTL-SDR Analysis Finds Action Cameras to Blame for GPS Signal Loss on Drones
Looking for answers as to why drones lose GPS lock, Spychalski found an unusual culprit: RF interference from on-board action cams.
Drone enthusiast Paweł Spychalski has published a video which demonstrates a surprising source of navigational noise in GPS-equipped devices, proving his point with measurements captured by a low-cost RTL-SDR software-defined radio: high-definition video cameras.
Highlighted by RTL-SDR.com Spychalski's video investigates issues drone users have experienced with GPS-based satellite navigation when they fire up on-board video cameras. While theories as to the root of the problem typically centre around the power draw of the camera and the overall drain it puts on the battery with the rotors running at the same time, Spychalski used an RTL-SDR to root out the real culprit: Radio-frequency interference (RFI).
"You might believe it or not (today I will prove it, however) that HD cameras, especially cheap ones, can be responsible for GPS problems on your drones and model airplanes," Spychalski explains. "The majority of HD cameras (RunCam Split, Runcam Split Mini, Foxeer Mix, Caddx Tarsier) generate RF noise on different frequencies. Some of them on 433 MHz, some on 900 MHz, but most of them also at around 1 GHz - just where one of the frequencies used by GPS signal sits. As a result, many GPS modules are reported to have problems getting a fix when the HD camera is running."
One of the features of a software-defined radio is the ability to use it as a spectrum analyser across a range of frequencies. Using the RTL-SDR, Spychalski demonstrates interference when a cheap — and presumably badly-shielded — HD action camera is switched on, particularly on the Industrial Scientific and Medical (ISM) bands and the frequencies used for GPS satellite reception.
Sadly, there aren't many choices available in terms of addressing the fault. The most obvious would be upgrading to a better-quality camera with improved shielding; an alternative would be to attempt to shield the camera from the GPS receiver with foil or a custom housing. Sadly, even more expensive cameras can exhibit the flaw: one comment on Spychalski's video claims to have experienced the same issue with a high-end GoPro Hero 7.