Richard Clark wrote:
On 28 Jul 2008 04:03:29 GMT, Ed
wrote:

About as well as it flows up the center conductor, possibly. You
don't think that just because the cable is buried that RF flow on the
shield conductor is prevented, do you?

Hi Ed,

I think Jonesy is fairly safe in his presumption. The classic work
performed by Brown, Lewis, and Epstein pretty conclusively reported
the nearly complete attenuation of direct driven RF currents in ground
radials at 3MHz.

75 feet of buried shield would seem to be quite snubbed by the
proximity of earth over much of the range of frequencies reliably
operated from a multi-band HF vertical.

Of course, adding a choke can't hurt.

73's
Richard Clark, KB7QHC

What Richard neglected to specify is that the work of B, L, & E shows
that there won't be significant current on the *outside* of the shield
because of the burial. The current on the *inside* won't be affected.

What's unknown is whether there was significant current on the outside
during the measurement with the shorter cable. If so, the cable and
probably the person doing the measuring became part of the antenna and
would therefore affect its impedance.

Roy Lewallen, W7EL