"Cecil Moore" wrote
If there is not a Z0-match to the feedline at the feedpoint, some
of the antenna current reflected from the open end of the antenna
leaks back into the feedline and makes it's way back to the source.
A TDR will register reflections both from the feedpoint and the
open ends of the antenna.
_________________

Not that this changes the essential point Cecil writes about, but...

The waveform transitions of most TDRs have bandwidths far greater than the
matched bandwidths of typical antennas, so the antenna system would produce
a reflection of the TDR pulse even _with_ a Zo match to the feedline at/near
the design frequency of the antenna.

For that reason a TDR is a relatively useless means to measure the
performance of an antenna, unless the bandwidth of the pulse is contained
within the matched bandwidth of the antenna, and that pulse is modulated on
an r-f carrier in the spectrum that the antenna is intended to radiate well.
The link below leads to an accurate measurement of a broadcast TV transmit
antenna system I made some 35 years ago, using this approach. This system
used about 1,550 feet of 6-1/8" OD, 75 ohm coaxial transmission line.

This measurement might also interest those who think that discrete
reflections do not exist inside a transmission line.

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

RF