"Dr. Honeydew" wrote
Oh, and we thought to do another experiment. While the generator was
operating, we sent a short burst of RF down a 50 ohm transmission line
to the generator's output. Because the power measurements seem to say
the generator's output resistance is very low, we thought we would see
a return pulse, delayed by the round-trip time down the 15 meters of
high-quality cable. But we didn't see any echo. What could be going
on? We double-checked everything, and even looked into the line next
to the generator with a high impedance probe. We can see the burst
going in there, but still nothing comes back.
____________

Below is a link leading to a documented, real-world RF pulse measurement to
think about.

The reflection results from an antenna mismatch at the far end of ~1,600
feet of air-dielectric transmission line. A directional coupler and
calibrated, step attenuator allow for accurate measurement of the weak
return pulse amplitude in the presence of the much greater incident pulse.

Note that the reflection is (barely) seen even in the incident display,
time-aligned with its location in the reflected display.

Reflections DO exist in such systems, but measuring them requires
appropriate instrumentation and methodology.

http://i62.photobucket.com/albums/h8...easurement.gif

RF