On 10/26/2014 7:22 AM, gareth wrote:
Setting aside the mistaken belief that even licensees of several
years' standing have that a short antenna will radiate all the power
that is fed to it, even long antennae do not do that!

You are correct. Antennas have some loss as do all things.

Consider the terminated and very-directional Rhombic with legs that
are several wavelengths long; the reason for the termination is to
absorb the power that does not get radiated and to prevent it being
reflected and so making the Rhombic bi-directional instead of
uni-directional..

A rhombic antenna is not a short antenna. It is terminated because it is
designed to be a traveling-wave antenna and not to be a standing-wave
antenna. Please do not compare apples and airplanes.

Also, consider the following, if shorter (than the Rhombic) antennae
radiate all the power fed to them, there would be no advantage to
extending the length of any antenna because the shorter bit would
have radiated all the power, and there'd be nothing left for the
longer bit to radiate.

See my statement above. A rhombic might not radiate all the power fed to
it. As you say, it might be terminated by a resistance. However the
current in the rhombic will cause radiation from the wires with great
efficiency. The purpose of the rhombic is directionality, not efficiency.

As it is short (and unterminated) antennae only radiate a small
proportion of the power that is fed to them, and that which is not
radiated is refelcted back to the feed point considerably
out-of-phase with the incident power and so presenting a very
reactive impedance. (Yes, OK, on the way back from the reflection, a
bit more might get radiated, but I suspect that the out-of-phase wave
affects the EM fields thereby reducing the radiative capability)

The hallmark of a rhombic is that is long compared to the wavelength of
operation in order to achieve directionality (that is, gain in a
particular direction).

If you wish to discuss the difference between standing-wave antennas and
traveling-wave antennas, I would first suggest you learn the difference
between the two so that you can carry on an intelligent dialog.

Was my response to you abusive?