I don't know if it is best to ask this question here, or on drones.stackexchange.com, but I think that I am more likely to get a good answer here even if i might have to provide a bit more background.

I experienced this problem on a FPV drone. The drone has an NTSC/PAL camera whose video feed goes into a flight controller (FC) with a built in chip that overlays some important information. The video feed then goes into a video transmitter (VTX) that transmits the signal to the pilot on the ground.

The problem I had was that I powered the camera and VTX directly from the battery via a 5V regulator, while the FC was powered via an electronic speed controller which I assume affects the ground in some way before it reaches the FC.

The problem I had was exactly the same one as this question, and the answer also helped me. I know the problem is caused by a lack of common ground, however what I still don't understand is how a lack of common ground between the FC, camera and VTX can cause the OSD to flicker or even disappear while the video feed from the camera is perfectly fine. I would have thought that the whole video feed would become affected if there was a ground loop.

  • \$\begingroup\$ Lack of common ground is the very opposite of a ground loop. If the flight controller needs to talk to the video system there MUST be a ground connection between them. A ground loop means two alternative ground paths form a loop, which picks up magnetic interference (hum, e.g. from motor currents). \$\endgroup\$ Oct 15 '20 at 17:54
  • \$\begingroup\$ There is a ground connection between the flight controller and the video system, but it goes through the ESC which causes interference. I'm sorry if I got the terms wrong. By lack of common ground I meant that there was a difference in potential between the ground points, which, according to Wikipedia, is the definition of a ground loop \$\endgroup\$ Oct 15 '20 at 18:11

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