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Jim Lux · March 7th 08, 05:46 PM posted to rec.radio.amateur.antenna

wrote:
I have searched quite a bit for evidence that states that performance
of antennas can be rated by it's size. Formulas do not refere to
radiator size or volume
and aparture is referenced to gain. I understand that sort of thinking
based on Yagi design
but the idea that all small radiators are inefficient is rather
ludicrouse. My work, based on
the sciences of the masters, show that a efficient radiator can be any
size,shape and
configuration as long as it
is in equilibrium . Period
No where can I find reference to "size" in what the masters state
Regards
Art

The work by Chu (Journal of Applied Physics, p1163, v19, Dec 1948) and
subsequently by Harrington (IEEE Trans Ant & Prop, V18#6, Nov 1965,
p896) , Thiele (IEEE Trans on Ant and Prop, v51, #6, June 2003, p1263)
and later others, discusses fundamental limits on performance. Watch
out, though, for the assumptions in the constraints (e.g. whether the
device attached to the feedpoint is reciprocal), and, of course, where
the boundary of the system is.

Watch out also for the definition of "Q", which in this context is the
ratio of stored to disspated/radiated energy, not the ratio of center
frequency/bandwidth.

In short, there is a tradeoff between Q, directivity, and size. And,
because high Q implies high stored energy, for physically realizable
antennas with loss, efficiency is in the mix too.

Googling "chu harrington limit" often turns up useful stuff.