"Cecil Moore" wrote
...

Here's a question for you: If the feedpoint impedance of a loaded
standing-wave (mobile) antenna is purely resistive, how could the
reflected wave arriving at the feedpoint have undergone anything
except a 180 degree phase shift?

There are the two possibilities: See:
http://paws.kettering.edu/~drussell/...t/reflect.html

1.Reflection from a HARD boundary "at a fixed (hard) boundary, the
displacement remains zero and the reflected wave changes its polarity
(undergoes a 180o phase change) "

2. Reflection from a SOFT boundary " at a free (soft) boundary, the
restoring force is zero and the reflected wave has the same polarity (no
phase change) as the incident wave "

So if the feedpoint is in distance 1/4 WL from the end you have 0 or 180
degree phase shift.

Which case is in antennas?
S*

Why is the feedpoint impedance of a resonant short loaded antenna
usually less than that of a 1/4WL antenna? Because the radiation
resistance is lower and the I^2*R losses are lower. But all resonant
shortened monopoles are 90 degrees in electrical length. Anyone
arguing against that fact of physics is just ignorant of how standing-
wave antennas work. That includes some otherwise knowledgeable
"gurus", incapable of admitting a mortal mistake, who post to this
newsgroup.
--
73, Cecil, w5dxp.com