Yeh-- Except that you need 2 WIRES! (unless both lengths to the coax
connector are the same length, from where "the wire" is at! to keep
the directional coupler at the same physical place(s) when makeing
measurements) As power is induced at one end of the coax, it can be
sensed , the opposite direction, by the sampling line- basis for an
SWR bridge-- Also works at microwave, with slot in waveguide to another
attached waveguide section- one end sealed (these are indeed called a
"directional coupler" ) Jim NN7K

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?