On Oct 3, 3:35*pm, Chevy454 wrote:
On Fri, 03 Oct 2008 10:20:44 -0700, Roy Lewallen
wrote:

I've found this method to be very ineffective in choking common mode
feedline current -- an effective sleeve requires a high impedance for
the outer coax structure, which this doesn't provide. So your dipole
impedance and performance will depend on the length and orientation of
the feedline and the ultimate path to ground for the common mode
current. You'll probably need to trim it when connected to the rig
you'll be using, grounded (or not) as it will be when used.

That's unfortunate, because I am looking for a simple arrangement.

What if I just hang a wire dipole vertically from the mast (= bendy
Black Widow crappie pole) with a PL-259 at the feedpoint? *How much
would the coax feedline have to stand off from the dipole to keep from
interfering with its operation? *I can't pull it too tightly away or
the pole will bend.

Ken KC2JDY

The vinyl on the outside of coax has some fairly poor RF insulating
qualities.
A number of CB antennas were built like this and the end of the braid
would often arc through the vinyl if illegal power was used. One of
the manufacturers changed the way they were making them by embedding
wires on the inside of the fiberglass tube that was used to house the
antenna. The wires replaced the shield. Another design is to replace
the folded back shield with a trumpet shaped tube. This is common
today on WiFi antennas. I have one for 6M that has the coax running up
through some EMT tubing. The coax is held centered inside the tubing
with little blocks of styrofoam. A few years ago the PVC coupling I
was using to fasten it to the mast cracked. I repaired it by wrapping
with fiberglass and have had no problems since.

Jimmie