This helical antenna calculator estimates the gain and key dimensions of an axial-mode helix. Enter the number of turns, spacing, and wavelength above for gain and beamwidth.
Formulas (axial mode, Kraus)
Circumference C ≈ λ Spacing S ≈ λ ÷ 4 Gain G ≈ 15 × (C/λ)² × N × (S/λ)
Example
N = 10 turns, C = λ, S = λ/4: G ≈ 15 × 1 × 10 × 0.25 = 37.5 ≈ 15.7 dBi.
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Frequently Asked Questions
How do I calculate helical antenna gain?
For axial mode, gain is about 15 times (C/lambda) squared times the number of turns times S/lambda.
What is axial mode?
It is the end-fire mode where the circumference is about one wavelength, giving high directive gain along the axis.
What spacing should a helix use?
About a quarter wavelength per turn, giving a pitch angle near 12 to 14 degrees.