This is one type helical antenna where the main radiation mode is along the axis or boom with a narrower beam respect to the axial helix but offset by having larger side lobes.
As usual all results: AS IS, no responsibility assumed.
The Hansen-Woodyard design specifies the spiral separation.
Dimensions are wire centre to centre.
For a standard custom design both S and D will be used.
Here we also design an optimum antenna using the established criteria. This means that the optimum pitch will be determined giving rise to the length L. Max-Min boundaries will be given the wire diameter d and the the ground plane sizes.
We also include the dimensions of a suitable quarter wave line to match the antenna to the typical 50 Ohm line.