Enter the circumference of the helix and the turn spacing (pitch per turn) into the calculator to determine the wire length of one helical turn; this calculator can also evaluate any of the variables given the others are known.
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Helical Antenna Formula
The following formula is used to calculate the straightened wire length of one helical turn (one wrap) of a helical antenna:
L_{turn} = \sqrt{C^2 + S^2}Variables:
- Lturn is the wire length of one helical turn
- C is the circumference of one turn of the helix
- S is the turn spacing (pitch per turn), i.e., the axial advance per turn
- N is the number of turns (optional: total wire length Ltotal = N·Lturn; axial length/height H = N·S)
To calculate the wire length of one helical turn, square the circumference and the turn spacing, add them, and then take the square root of the result.
What is a Helical Antenna?
A helical antenna is an antenna made by winding a conductor into the shape of a helix (like a spring) around an imaginary cylindrical or conical form. In axial-mode operation, a helical antenna commonly produces circular polarization and a directional radiation pattern; in normal-mode operation (typically much smaller relative to wavelength), it more closely resembles a short dipole/loop with predominantly linear polarization. Key geometric parameters include the helix diameter (or circumference), the turn spacing (pitch), the number of turns, and the overall axial length. These parameters strongly influence operating characteristics such as gain, bandwidth, and radiation pattern. Helical antennas are widely used in applications such as satellite communications and space communications where circular polarization is beneficial.
How to Calculate Helical Antenna?
The following steps outline how to calculate the wire length of one turn of a helical antenna:
- Determine the circumference of one turn of the helix, C (length units).
- Determine the turn spacing (pitch per turn), S (length units).
- Use the formula: Lturn = √(C² + S²).
- If needed, compute total wire length using Ltotal = N·Lturn (where N is the number of turns).
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge for a helical antenna. For C = 30 cm and S = 7 cm, the wire length of one turn is Lturn = √(30² + 7²) cm ≈ 30.8 cm.
Circumference of one turn, C (cm) = 30
Turn spacing (pitch per turn), S (cm) = 7
