Tom, KA6RUH wrote:
"You`re right in a certain mathematical sense, but that definition isn`t
correct as Roy pointed out in defining superposition."

Or in conjugate matching for that matter. The discussion was: Is an
antenna a linear device, meaning does it produce amplitude distortion?

Amplitude distortion comes from a nonlinear relation between imput and
output. It has nothing to do with has the amplitude grown larger or
smaller in the antenna? I think the majority of antennas have an output
which is a reasonable approximation in form to their input. That goes
for frequencies too. The response won`t be the same for all frequencies,
but you`re not likely to find new frequencies on the output of the
antenna that aren`t on its input.

Superposition says that when a number of voltages (distributed in any
manner throughout a linear network) are applied to the network
simultaneously, the current that flows is the sum of the component
currents that would flow if the same currents had acted individually.

As Cecil said, nonlinearity produces new frequencies. Good antennas
don`t do that, superposition or not.

Best regards, Richard Harrison, KB5WZI