Dr. Slick wrote:
"The funny thing about this is that you cannot say that the 50 ohms in
the center of the chart is a "resistive" 50 ohms as there is very little
real resistance in the average antenna."

Resistance is defined as real. That is, current is instantaneously
proportional to the voltage.

Any efficient antenna has a high ratio of radiation resistance to loss
resistance.

Resistance is the ratio of in-phase voltage to current accepted by an
antenna. Part is made by loss in the antenna. part is made by radiation
from the antenna. They are often represented by an equivalent circuit of
two resistors in series.

Dr, Frederick Emmons Terman says of radiation resistance:
"This is the resistance that, when inserted in series with the antenna,
will consume the same amount of power as is actually radiated. ---it is
customary to refer the radiation resistance to a current maximum in the
case of an ungrounded antenna, and to the base of the antenna when the
antenna is grounded."

Best regards, Richard Harrison, KB5WZI