on yagi's and other antennas with matching networks you usually just see the
matching network. i use it the most on my beverage antennas which kind of
look like long transmission lines and also to find faults in transmission
lines themselves. with 25 lines or so ranging from about 50' to 500' or so
it makes for a quick check... especially in winter.

"Tam/WB2TT" wrote in message
...
Dave,

What happens when you ping your antenna? Clearly the spectrum of the pulse
is wider than the bandwidth of a typical antenna, but is there any useful
information?

Tam/WB2TT
"Dave" wrote in message
...

"Mike Coslo" wrote in message
...

* 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 -

i use one regularly in my station here. most people don't use them
because
a simple swr meter is adequate for testing most antenna./feedline
combinations in use by amateurs.