"joe" wrote ...

Your problem is not understanding the motion of charges in the antenna.

Sure, the derivative of a sine wave is 0 at the peak,

It is the math

but this does
not directly translate to the motion of the electrons
at specific locations in the antenna.

Look at the antenna current as an electron oscillating
back and forth between the ends. The position over time is described
by a function. Throughout the entire length, the electron is
changing velocity (accelerating).

Hint: the _voltage_ at the feed point may be described by a sine wave.
Your challenge is to determine how the electrons move in response
to that sine wave.

Part of understanding this is knowing the difference between what is
happing as time progresses at the different parts of the antenna.

The trick to understanding this is to carefully do and understand
the mathematics that are involved.

It is not easy to understand you. Math says that "the derivative of a sine
wave is 0 at the peak," next that it is not true and next that math is
always right.

Electrons flow free in feed line and are compressed in ends. After short
rest they come back to supply unit.
S*