* wrote:

They make an instrument called a Time Domain Reflectometer,
you hook it up to transmission lines and it sends out a pulse
and times how long it takes to get back.
The time it takes, reflected pulse polarity, and height says a lot about the
line.
Used for finding faults on telco/cable lines.
Does the same thing with RF lines.
Matched well, no pulse, but you can even see connectors on some of these
TDR's
Googleit, too

Fascinating stuff! Why don't we use them more for ham radio? this page:
http://www.epanorama.net/circuits/tdr.html even has a diagram for a
homebrew pulse source and diagrams for hooking up same to an
oscilloscope. While not giving SWR, it would show up any connector
faults and crimps in the cable.

- Mike KB3EIA -