BamThwock et al;
The ADF has two main receiver errors as you turn onto a track (ignoring general lack of accuracy
).
Quadrantal error is caused by signal reflections off the airframe, and should be calibrated out in any self respecting transport aircraft.
Dip, on the other hand, is a geometric fact of life that is a function of range, altitude and bank angle. The ADF needle points at where the transmitter is in relation to the nose of the aircraft. If you imagine flying towards the beacon with 90 degrees of bank (briefly!!), the needle will point at an angle that depends on your altitude and range. When turning onto a course, the needle has a tendency to point towards the lower wing by a few degrees, how much is a bit of guesswork. I don't know of any system that is able to correct for this!
In the real world, it is rarely an issue these days as most approaches are flown by positioning the aircraft using the FMS, with the ADF being used to confirm we have no map shift. I don't know about the 737, but in the Challenger we're even allowed to do it this way on an OPC!
VC10 - Good luck with the sim.