I find it hard not hear WBZ underneath the null (phase) on a
number of frequencies
Please don't overlook the phasers Keith. The Quantum is a fine phaser,
but it is not meant to be baked by RF. I'd look at that even before
the Wellbrook amps. Years ago it was noticed that John Bryant's
Quantum on Orcas Island was yielding Vancouver, BC stations in many
nulls.....they were 25 miles away, admittedly over salt water, and
pretty much qualified as his nearest locals.
If the other phasers also have active elements, I'd certainly suspect
them as well.
best wishes,
Nick