"Yuri Blanarovich" wrote in message
...

RF current "makes the corner" around to the outside surface of the
shield in coax all the time. If it didn't we wouldn't need choke
balun's.

We need RF chokes and baluns to supress curents induced on the shield from
the unbalance at the antenna feedpoint.

Actually what oftentimes happens with a coax feed is that the RF
current leaving the inside of the feedline shield can flow in two
directions. It can flow down the antenna element half connected to the
shield (desired path), or it can flow down the outside of the shield
(undesired path). The electrons are dumb, all they are looking for is
the path of least resistance. They can't tell that the metal surface
on the outside of the coax isn't supposed to be part of the antenna.
The only way to keep current from flowing down the shield is make
the antenna element-half connected to the shield look like a lower
impedance than the outside of the shield. If you place ferrite beads
around the outside of the shield, this will raise the impedance of the
shield path, thereby diverting the bulk of the RF current into the
element-half and off of the shield's outside surface.

Sooo, according to W8JI "teachings", RF current gets induced onto the
outside surface of tubing, then crolls around the edges and goes inside
the tubing?

As per K4FMX's comments, this can only happen if there is a
center conductor inside the tubing, or if the tubing diameter is greater
than ~1/2 wavelength in diameter, otherwise the inside of the tubing
looks like a circular waveguide beyond cutoff. This is why coax
of a given diameter becomes useless above a certain upper frequency
limit. Once the I.D. of the coax becomes a significant fraction of a
wavelength in diameter, the coax will start to support propagation of
waveguide modes (e.g. non-TEM modes). At HF frequencies, even
large diameter tubing is well beyond waveguide cutoff, so there is no
concern about "corking" open tubing with no center conductor (it
corks itself).

73, Mike W4EF.............................................. .......

Sooo, we should cork the elements, or the current will get confused inside
of dark tubing elements, Eh?
Any formulas to calculate the resonance of such "antenna"??