On Mon, 15 Feb 2010 19:21:15 GMT, Owen Duffy wrote:

A current balun at the feedpoint will not of itself reliably eliminate
common mode current on the OCF feedline, nor will an 'isolator' of itself
at another point reliably eliminate common mode current in the shack.

Hi Owen,

Maintaining your DC analogy (argumentum), the isolator (if, indeed, we
mean isolation of CM from the shack) can be achieved if the drop
line's coaxial shield at the bottom end is immediately driven into an
RF ground, AND the line routed on or beneath ground to the shack
(where it can emerge from ground for normal considerations of
terminating to the rig).

Routing the transmission line (coaxial cable) in close proximity to
ground alone (no separate connection to ground) for a sufficient
distance could easily eliminate common mode RF from the shack.

Thus, we would have a tripole antenna with three off-centers. The
vertical element would be grounded at the end and would present a
wealth of marketing opportunities. It wouldn't necessarily be a bad
antenna (performance-wise), but the design variables could eliminate a
significant population of customers.

73's
Richard Clark, KB7QHC