Gene, W4SZ wrote:
"What went wrong?"

Sorry, I can`t say because I haven`t followed this thread closely.

Surely the signal follows the path of the turns on a coil. Movement of
electrons is slothful but they are urged by the fields sweeping across
them.

Terman has but one mistake in his 1955 opus and it is only a
typographical error which is obvious, kilocycles instead of megacycles
or something of the sort and doesn`t affect understanding the subject.

Terman says on the "Mechanism of Operation of the Traveling-Wave Tube"
at the bottom of page 678:
"The applied signal propagates around the helix and produces an electric
field at the center of the helix that is directed along the helix axis.

That`s been read and re-read over 50 years and even repeated in the
"Lenkurt Demodulator". There is no chance it is wrong.

Best regards, Richard Harrison, KB5WZI