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Old March 23rd 10, 08:40 PM posted to rec.radio.amateur.antenna
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Default Measuring antenna loss: Heat balance?

Joel Koltner wrote:
Hi Tim,

"Tim Shoppa" wrote in message
...
On Mar 22, 9:24 pm, "Joel Koltner"
wrote:
I think his method, especially for physically compact antennas and
feed systems which tend to have very low radiation resistance at HF
frequencies, is a great check on theoretical calculations. There has
to be a meeting point between mathematical models/NEC and reality and
he is working at one such point.


Agreed -- the controversy comes into play in that he ends up computing
electrically-small loop antennas as being upwards of 70-90% efficient,
when everyone "knows" that such antennas are typically 10% efficient.
He even goes after Chu/Wheeler/McLean/etc. in suggesting that the
fundamental limits for the Q of an ESA are orders of magnitude off
(slide 47), and that's pretty sacrosanct terriority (see, e.g.,
www.slyusar.kiev.ua/Slyusar_077.pdf -- even the Ruskies buy into the
traditional results :-) ).



One wants to be careful about "Q" and Chu, etc. If you haven't
actually read the paper, you might think that Chu is talking about Q as
in filter bandwidth (e.g. center frequency/3dB bandwidth), but it's not.
It's the ratio of energy stored in the system to that radiated/lost.
For some systems, the two are the same, but not for all.
 
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