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Old September 14th 09, 06:03 PM posted to rec.radio.amateur.antenna
Richard Fry Richard Fry is offline
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First recorded activity by RadioBanter: Jun 2006
Posts: 440
Default Spherical radiation pattern

On Sep 14, 11:15*am, Art Unwin wrote:
Now we have something that meets reality, where increase in current
applied creates an increase in radiation...


NOW ?? This has been true forever.

... and where the model is seen
to be a boundary consisting of particles bound to each other! This is
basically implied by Maxwell's equations as illustrated by the
computer programs where radiation increase is proportional to the
decrease of impedance of the energy robbing metallic radiator etc


Decreasing the feedpoint impedance of an antenna to 0 +j0 ohms (if
that were possible) does not maximize radiation.

The first term in the antenna impedance specification in a practical
antenna consists mainly of radiation resistance -- which is required
in order for radiation to occur. Radiation resistance is a function
of the electrical length, diameter and form of the radiator exposed to
space. If it is zero then there is no radiation.

Higher radiation resistances lead to higher efficiencies for the
antenna SYSTEM, because then the power radiated can be much greater
than what is dissipated in the relatively smaller I^2R losses of the
system.

RF