Yuri, K3BU wrote:
"W8JI used this picture (Fig 10) to "see, it is constant".

But that was only by specification. It`s the same as saying, "Let`s say
the line is lossless".

The text reads:
"The loading coil acts as the lumped constant that it is, and
disregarding losses and coil radiation, maintains the same current flow
throughout."

This says that in the impossible case of zero radiation and zero loss,
the coil current is the same at both ends of the coil. This is close
enough for a coil at 50 Hz, but unlikely at 5 MHz.

A real loading coil such as a bug catcher, has a real length. The
combination of incident and reflected waves at each point along the
length of the antenna produces a different voltage, just as seen in a
transmission line. This effect prevails in an antenna, too.

Just as on a transmission line, the voltage variation represents an
impedance variation. Impedance is high at the open-circuit end of the
antenna , and it it is low 90-degrees back from that open circuit. Since
some length is filled with the coil, there is a difference in volts at
the ends of the coil due to the standing wave on the antenna.

The feed paths to the coil are unbalanced as shown in Fig 6. That is not
shown in Fig 10 which is meant to show the difference in antenna current
above and below the coil, not what happens in the coil itself. The
authors specify an idealized coil which has the same current in and out.
This is only a declaration, not a real world situation.

Best regards, Richard Harrison, KB5WZI