Cecil, W5DXP wrote:
"If the transmitter is linear (like the antenna is linear), i.e.
Class-A, 1/2 or more of the generated power weill be lost in the
source."

True, that would be an equalizer between reception and transmitting
system efficiencies of antennas, but Class A isn`t the only way to get
linear amplification, Hi-Fi nuts to the contrary not withstanding. Class
B is often used to combine efficiency with high undistorted output
capability. Class B amplifiers are biased to cut-off so they draw no
current when there is no signal input. A class B amplifier may have 60%
efficiency at full power output, for example. Such an amplifier will
have only about 30% efficiency at 1/2 of its maximum power output.

Turman writes on page 354 of his 1955 edition:

"With the largest signal that the (Class-B) amplifier can be expected to
handle satisfactorily, Emin/Eb will be small, and the actual efficiency
at full power is commonly of the order of 60%."

The receiving antenna can never be more than 50% efficient due to
re-radiation which I don`t seem to be able to explain. Sorry.

Best regards, Richard Harrison, KB5WZI