Richard Harrison wrote:
Cecil, W5DXP wrote:
"A TDR will register reflections both from the feedpoint and the open
ends of the antennas."

Why reflections from the feedpoint if the antenna matches the feedline?

A traditional TDR sends a fast rising step or narrow pulse. The
condition for no reflection is that the load impedance equal the line
impedance over at least the bandwidth of the energy in the step or
pulse. Depending on the TDR system, this could be well into the tens of
GHz. Even a very broadband antenna doesn't meet this requirement at the
feedpoint, so a reflection will occur.

Long ago I looked at a small dipole with a TDR system, and I've seen the
same result published several times since. What you see resembles a
damped square wave, the general square wave shape being due to multiple
reflections from the ends and feedpoint, and the damping due to
radiation. The top of each "cycle" of the square wave rises, however,
because the impedance of the transmission line formed by the two dipole
halves increases in impedance from the center to the ends.

Roy Lewallen, W7EL