John Smith I wrote in news:etus10$hop$1
@nnrp.linuxfan.it:

I have been searching the internet, it seems to me someone would have:
....
2) Constructed gas insulated coax enclosed in a glass or plastic tube
with sufficient gap in the outer conductor where observations could be
made to see if "reflections" or other observable anomalies, and voltage
and current observed.
....

Been done already, it is called a slotted line, and it is one of the
methods of direct measurement of VSWR. Not only did it allow direct
measurement of VSWR, but the position of the pattern could be observed, and
located wrt a known mismatch (typically a s/c) at the load plane. thus
allowing calculation of the complex load impedance.

Owen