Richard Harrison wrote:
Inductors are used to replace a missing length of an antenna which often
would be located at the inductor. The coil is an antenna length
surrogate. Its delay and impedance characteristics match that of the
missing length of straight wire.

Hi Richard,
I know what you mean and it is not an *exact* match. (And you did
not say or imply that it was an exact match.) From a 1/4WL monopole
to a loaded mobile antenna, the feedpoint impedance can drop from about
35 ohms to about 12 ohms. That probably means that the in-phase reflected
current has increased from one configuration to the other and the
out-of-phase reflected voltage has also increased. In other words, the
antenna reflection coefficient is higher for the loaded monopole which
would make it less efficient.

We know that, at resonance, the net feedpoint voltage is in phase with
the net feedpoint current. But the component forward and reflected
currents do not have to be in phase. And the component forward and
reflected voltages do not have to be 180 degrees out of phase.

In fact, there is a considerable amount of interference going on at
the feedpoint of a standing-wave antenna. If one calculates or
measures the s11 reflection coefficient s-parameter at the feedpoint
of a dipole, it will have a magnitude in the ballpark of about 0.85
--
73, Cecil http://www.qsl.net/w5dxp



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