From whom or where is the variation of VOR obtained?

The variation of VOR, or VHF Omnidirectional Range, is specifically obtained from the VOR station itself. This is because each VOR station broadcasts a magnetic reference that indicates a specific radial. This radial is based on true north, and the variation is determined by the geographical differences in magnetic north and true north at the location of the VOR station.

Each VOR station has a set geographical location, which means that the magnetic variation will be unique to that particular station's location. Thus, pilots receive accurate navigational information tailored to that specific zone. This ensures that as they navigate using the VOR system, they can correctly align their aircraft with the radials that lead them to their intended destination.

Other choices like aircraft flying the route or ground control stations do not provide the inherent magnetic data that the VOR station itself offers. Similarly, while a combination of airborne and ground data might provide valuable navigational context, the fundamental variation information specifically stems from the design and location of the VOR station.