It is a long (very long!) time since I studied VOR radials, but I seem to recall they work differently to, say, an NDB, in one very important way. They radiate radials and not a single radio signal. Thus when built, they are aligned as accurately as possible to magnetic north and that becomes their permanent reference. As time passes, magnetic north changes, as in annual change in magnetic variation.
Thus an error creeps in and the VOR no longer aligns accurately with current magnetic north.
Thsi will explain why you cannot measure the true direction from a VOR to another point, apply variation, and obtain the correct radial. Even when using the VOR rose on a chart it will not necessarily give you the correct radial (apart from the lack of accuracy in setting and measuring) even if aligning with the 'flute'. The only way to obtain the exact radial is to accurately position a VOR receiver over the geographical position required, tune in the VOR and measure the radial.
Anyone who has seen a VOR station will recognise it immediately - it is a low circular building with lots of vertical 'posts' around the perimeter of its flat roof - not easily moved. However, I suspect modern VORs might be electronically 'rotatable' to align with current magnetic north.
Last edited by roadrabbit; 8th Dec 2017 at 21:42.
Reason: clarity