There is video of the Apollo 15, 16, and 17 lunar modules lifting off from the Moon. I recall watching it live for Apollo 17 at least. I know the images were captured by a camera mounted on the lunar rover, and at least in the case of Apollo 17, the camera was remote operated from Earth to tilt up to follow the module's ascent.
My question is: what was the signal path between the rover and Earth? Was there a direct radio link between the rover and Earth ground stations or was it relayed via the LM, CM or some other satellite? What other purpose did that link serve other than video feed from the rover?