To scope the secondary I just remove the RF earth and feed the signal into
the base and use a probe as an aerial, as far away as you can pick it up
still. Even then if someone walks past [say] 8 foot away on a medium sized
coil, you can see the effect on the scope.
There is a difference in the results gained between scoping them separately
(probably the correct manner) or with both sitting in situ on the coil, but
only around two or three kilohertz, I find on mine. As Gary states it's
best to learn doing them separately, first of all, to avoid possible
confusion.
Phil