Tdonaly wrote:
"---I don`t have any better idea than you do what the current
distribution in any individual coil is. I suppose it depends on its
environment and its physical description."

Kraus` story of his discovery of the axial mode helical antenna starts
on page 222 of "Antennas". Kraus was a new Ohio State University faculty
member in 1946 when a famous scientist told him a helix wouldn`t work as
an an antenna as he had already tried it with no success.

The expert`s statement challenged Kraus to try for himself, and the rest
is history.

The first coil he wound was one wavelength in circumference and had 7
turns.. Kraus was pleased with the sharp end-fire beam of
circularly-polarized energy from the open end of the coil. Kraus found
the helical beam antenna had a resistive input and a wide frequency
bandwidth.

At low frequencies, outgoing and reflected waves along the helix were
almost equal in magnitude but as frequency increased, current
distribution changed dramatically in the helix.

At a circumference of one wavelength, there were 3 regions. Near the
antenna input, current decayed exponentially. Near the open end of the
helix, there was a standing wave for a short distance. In the middle
region, there was a relatively uniform current (small VSWR) which
extended over most of the helix. Kraus gives the plots of the currents
along the helix in Figure 8 on page 224.

Certainly, Tdonaly is correct. Different coils have different current
distributions, but Kraus` contribution interests me.

Best regards, Richard Harrison, KB5WZI