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Old June 8th 07, 02:05 PM posted to rec.radio.amateur.antenna
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Posts: 287
Default Real time proof of Poyntings vector


"Richard Harrison" wrote in message
...
Richard Clark, KB7QHC quoted Mike Kalinski`s question: "What do you mean
by equilibrium?"

Richard also asked: 'How do you distinguish directivity from gain?"

Only Art knows what he means by "equilibrium".

Gain, however, is well defined by common usage and defined by experts.
Gain and directivity are close relatives. Terman wrote on page 870 of
his 1955 opus:
"Directive gain depends entirely on the distribution in space of the
radiated power. The power input to the antenna, the antenna losses, or
the power consumed in a terminating resistance have nothing to do with
directive gain. Such factors are taken into account in terms of power
gain of the antenna which is defined as the ratio of the power input to
the comparison antenna required to develop a particular field strength
in the direction of maximum radiation, to the power that must be
delivered to the directional antenna to produce the same field strength
in the same direction. Unless otherwise specified the comparison antenna
is a lossless isotropic radiator."

I`m no longer completely in the dark about Gaussian antennas since
finding pages from St. Andrews University about them on the internet.
It`s an extension of optical principles used at somewhat lower
frequencies in the millimeter and microwave frequency wavebands. All
antennas can be scaled but are not always practical when made larger or
smaller. Until Art comes clean about his ideas, we probably won`t know
the likelihood of his success.

Best regards, Richard Harrison, KB5WZI

My first encounter with Gaussian antenna was with microwave relay paths and
"fly swatter" antennas.
A gaussian antenna is on top of the site building rof point straight up. the
beam is then reflected in the desired direction
by the fly swatter reflector that would be at about 300 ft up on a tower.
In this case gaussian antenna meant a parabolic reflector antenna whose
beam was further focused and cohered by a fresnel lens. No resemblence at
all to Arts definition.

Jimmie



 
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