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

"Cecil Moore" wrote in message
...
Mike Coslo wrote:
I'm a real dilettante in these matters, but why would a signal be
reflected if the impedance was incorrect, and not if it was correct?

Dunno why, but that's just the way it is. To see for yourself,
feed a 75 ohm TV through 1000 ft. of 75 ohm coax. Then feed
the same TV through 1000 ft. of 600 ohm ladder-line. How do
you explain no ghosting in the first case and lots of ghosting
in the second case? Seeing is believing.
--
73, Cecil http://www.qsl.net/w5dxp



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