Art Unwin wrote:

What one gains from this aproach is that any radiator
of any shape, size or elevation can provide figures in
the order of 100% as long as the radiator is a multiple
of a wavelength where it is resonant at exact and
repeatable measurements.

then Art wrote:

The use of the term "nearly" does not imply total accuracy.

Note that your use of the phrase "in the order of" does not
imply total accuracy, either -- even for radiators meeting
your criteria.

To use Maxwell's equations for accuracy one cannot introduce
metrics that are not absolute. 1/4 or 1/2 wave radiators cannot
supplant the "period" of a wave form and thus introduce
inaccuracies.

Apparently you believe that only full-wave radiators are
"perfect" (exactly 100% efficient).

However a full-wave, center-fed dipole has a radiation resistance of
about 2,000 ohms, and a feedpoint reactance exceeding 1,000 ohms
(capacitive). That impedance would present a very high VSWR to a
normal transmitter unless some kind of matching network was used.

Even if there was no matching or transmission line loss (or r-f ground
loss in the case of a monopole), that full-wave radiator still would
not be 100% efficient because of the ohmic losses encountered by the r-
f current flowing along the radiating structure (NOT the radiation
resistance).

RF