AngloPepper,
You are right - BCAR section R says something similar about "loop swinging" (i.e establishing quadrantal error corrections) being done as close as possible to the edge of promulgated range.
Anyone know why that is ? I would have thought that you wouldn't necessarily want worst-case SNR for quantifying quadrantal errors. Maybe it is to minimise multipath effects.
The AC 25-7A Flight Test Guide (credit safetypee) is similar in content to BCAR-R as regards ADF testing, but talks about testing at half-range.
B.