Ian... extreme lengths is right! I like the ferrite cores strung onto
the 240V lines.

I'm sure this approach would help if I wasn't on a graduate student
budget and living in an apartment (though maybe I could sneak around
and install snap-on ferrites on everything?)

After reading that article and thinking back a bit, I think a real
current balun would be worthwhile.

A previous incarnation of my "invisible" antenna used *one* length of
magnet wire to a SO-239 tuner center pin and used the balcony rail
connected to the ground on the tuner.

Switching to the "balun" and two legs reduced my electric(al/onic)
noise quite a bit. I think at least trying to enforce balance is
worthwhile. I guess I need to be prepared to spend some money if I
want to be able to choke off common mode currents on all bands .
I certainly am trying to tame a noisy QTH, but I've made some progress.
As is often the case, it was mostly *my* stuff causing the noise.
Still, I've got a few persistent sources. I know *some* of it is
radiated and I'm sunk there. My 6m antenna is a moxon rectangle with a
string of 60 or so #43 beads as a balun mounted on a fiberglass mast.
Everything it's picking up is radiated :-)

Roy, I'll do the impedance measurement on the balun input, just as a
matter of curiosity, and post the results.

First pass, I think, will be the 1:1 current balun, especially if the
MFJ balun's core is of a worthwhile material. I'll let the tuner do
its job.

I'm curious about what would happen with the 4:1 current balun, butI'll
have to order some cores.

-Dan