Dr. Slick wrote:
"Therefore, the reflected voltage can never be greater than the input
voltage for a passive network, and the reflection coeficient can never
be greater than 1 for such a case."

A reflection coefficient implies that transmission lines long in terms
of wavelength may qualify as passive networks.

At the open-circuit end of a long transmission line, current is
interrupted by the open circuit. Having nowhere else to go, energy in
the current wave must be accepted by the voltage wave which doubles on
the spot. 2X the incident voltage is the sum of the voltage in the
incident wave and the voltage in the new reflected wave as they are
in-phase. The reflected voltage is no greater than the incident voltage.
It is equal to the incident voltage. It`s the sum that doubles.

Best regards, Richard Harrison, KB5WZI