Thanks to Dave, Mark and Telemon - all very interesting and useful
suggestions. Once I get the wires up, I will try some of these
configurations. I have never had any problem that I could trace back
to, say, my PC or my TV, but maybe the beads will help clarify whether
these are problems.

Telemon, when I differentiated between beads and cores, I guess I
meant to differentiate between mounting styles - I think of beads as
"slipped over" the cord, while I think of "cores" as being
doughnut-shaped toroids through which the cords are "wound" several
turns.

It sounds like the beads or toroids would function better than the
rods for most RFI suppression purposes. Per Mark and Dave, it also
sounds like the more beads used, the better isolation one can achieve.

From what I gather, in addition to the specific points that each of
you made, the AC mains and RFI noise that the ferrites will help to
overcome is usually very local in nature, typically generated at one's
own house or *maybe* with one's immediate neighbor. It sounds like
they might be less effective on RFI picked up directly by the antenna
from, say, a scratchy high-voltage power line 150 yards away, or a bad
streetlight down the block, or the like.

Oh, to live back in rural Massachusetts again...I remember quiet
airwaves...

Thanks!
Bruce