Cecil Moore wrote:

Seems everyone must be suffering from post tramatic syndrome on this one.

Here's the bottom line.
Does a center-loaded mobile antenna have a cosine current distribution? No.

Does just the coil have a cosine current distribution? Close to one but
it may not start at zero degrees like a thin-wire dipole does.

Does displacement current have an effect? Yes, but the effect is
close to the same for the forward current and reflected current.

Do I^2*R losses have an effect? Yes, but the effect is close to
the same for the forward current and reflected current.

Does radiation "loss" have an effect? Yes, but the effect is close
to the same for the forward current and reflected current.

Whatever effects exist that affect the current, the forward current
and reflected current are affected close to equally.

The net current anywhere on the antenna is still the phasor sum of
whatever forward current and reflected current exists at that point.

Any phase shift through the coil is multiplied by two by the two
currents traveling in opposite directions with opposite rotations.

Can one subtract the number of degrees occupied by the conductors
from 90 degrees to get the number of degrees occupied by the coil?
No, it's not that simple.

Is the current at the top of the coil higher than predicted by the
above simple calculation? Yes.

Does the coil occupy zero degrees? No.

If the coil doesn't occupy zero degrees, the net current at the bottom
of a coil and at the top of the coil cannot be the same value when the
coil is located in the middle of an electrical 1/4WL antenna.

Are there special cases where the magnitude of the current at the top
and bottom of a coil can be equal? Of course, but the typical loaded
mobile antenna is not one of those special cases!
--
73, Cecil, W5DXP


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