Yep I use that configuration for a directional coupler/VSWR measuring
device some years ago. I ran the internal insulated lines up either side
of the coax (RG213) into a switch box and off to a DVM. I think I used
shottkey diodes.

Cheers Bob VK2YQA

Cecil Moore wrote:
I vaguely remember building a coaxial "slotted" line without
the slot when I was in college. We took a piece of coax,
stripped off about a foot or so of outside insulation, and
ran an insulated wire under the braid. We tied one end to
ground through a R=Z0 resistor and ran the other end
to a 1N34 rectifier. Anybody remember running a wire
under the braid to achieve an inductive pickup for
forward and reflected power?