Art wrote:
"I would disagree with the above as it has its roots in a large yagi
style where phasing is of the essence."

Kraus says on page 268 of the 3rd edition of "Antennas":
"The natural adjustment of phase velocity so that the fields from each
turn add nearly in phase in the axial direction accounts for the
persistence of the axial mode of radiation over a nearly 2 to 1 range in
frequency."

In Kraus` 1950 version of "Antennas" on page 178 he writes:
"A first-order transmission mode on the helix, designated T1, becomes
permissible when the helix circumference lambda in free space is of the
order of 1 wavelength."

I don`t argue with Terman or Kraus.

Best regards, Richard Harrison, KB5WZI