Richard Fry quoted Geoffrey Mendenhall who is responsible for the entire
Harris broadcast transmitter line design as saying:
"If the source impedance were equal to the 50 ohm line impedance, half
the transmitter`s output would be dissipated in its internal output
source impedance."

Mendenhall is wrong.

A Class C amplifier`s "internal output source impedance" is largely
"dissipationless resistance" produced by the non-conduction time during
its RF cycle. A matched Class C amplifier typically produces
efficiencies exceeding 50% by a comfortable margin. That`s why they are
used despite their harmonic generating nonlinearity.

Best regards, Richard Harrison, KB5WZI