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Old March 25th 11, 03:30 PM posted to rec.radio.amateur.antenna
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Default Helically-wound Monopoles

On Mar 25, 9:53*am, John Ferrell wrote:
There are a lot of Hams who still think a short resonate dipole is
just as good as a full size dipole.


That would be true if everything was lossless. Unfortunately in the
real world, a short dipole *system* almost always suffers more overall
losses than a well-designed full size dipole *system*. In general, the
shorter the dipole, the greater are the losses in the process of
transferring energy from the source to the load. Short dipoles are
indeed efficient radiators of the *energy delivered to the antenna*.
The loss problems are in the energy transfer/delivery systems, not in
the energy radiating system.

The reason that a high-Q center loading coil system has less loss than
a 100% helical system is interesting. The impedance discontinuity at
the loading-coil/whip junction yields a lossless phase shift that
contributes to the electrical length of the antenna. It is a rare
"something-for-nothing" gift from the Antenna Gods.
--
73, Cecil, w5dxp.com
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