Axial-Mode Helical Antenna Calculator

This is my simple implementation of the ARRL Antenna Book design equations for the axial-mode helical antenna. The dimension limits are enforced to ensure axial-mode radiation. Larger C/Λ tightens the radiation pattern at the expense of circularity.

The 50 ohm matching techniques are discussed at length in the ARRL book. I have had good luck with the 1/4-1/2 turn close spaced matching technique, which sacrifices less bandwidth than a coax matching network, but more than building four short helicals in an array with the tapered parallel feed system.

Frequency Hertz * 106
Turns turns (at least 3)
C/Λ Circumference/Wavelength (0.75 - 1.33)
D/Λ Reflector Diameter/Wavelength (0.8 - 1.1)
S/Λ Turn Pitch/Wavelength (0.2126 - 0.2867)