DERG:
GarageYears sums it up pretty well, in part:
- The issue is not additional RF emission from spark-plugs, magnetos, or other, since the radios and antenna are NOT directional - such noise would be present irrespective of the aircraft's orientation with respect to the source station.
There is one other observation that must be considered
The interference is at the same level of "badness" whether the tower is
200 yards or many miles away resulting in very significant difference in Rx levels.
Please explain how any on board RFI source (which has to be at a relativly fixed level having no knowledge of distance to or direction of tower ) can account for that and all the other features of this problem.