"Wayne" wrote

Dead on explanation. Some have insisted that inefficiencies
result from antenna size and not from matching challenges.
_______

Kindly note that the radiation efficiency of an antenna _system_ is related
to its radiation resistance compared to other resistive losses present in
that antenna system.

It is possible to perfectly match the impedance at the feedpoint of an
antenna system to the impedance of the transmission line connected there.
But that antenna system still can have very poor radiation efficiency at
that frequency.

An example of this is a Z-matched, but electrically short vertical monopole
driven against a poor r-f ground connection such as a few buried ground
rods. Most of the available transmitter power is dissipated in the r-f
ground resistance, rather than being usefully radiated as e-m waves.