No Spam wrote:
Would a section of 1/2" copper pipe work as a good choke? Simply slid
over the coax?

I've seen lightning chokes where about a 8ft piece of copper pipe was
slide over coax to choke off a lightning surge.

If the pipe was attached at the outside of the coax, at the antenna feed
and have a length of 1/4, 1/2 wavelength, etc. (depending on antenna
type/length), I would suspect it would be an "easier" path for the rf
currents which were flowing on the outside of the coax, and they would
now choose the path of the pipe--wouldn't you? However, another way of
looking at this particular situation would be you just added another
element to the antenna!

However, I suspect you are suggesting chucking that (1/4?) wavelength of
pipe over the coax an no specific point and with no direct connection to
the coax; and, in that case, I would have to experiment, do research or
ask someone with experience ... however, I suspect not ...

Regards,
JS