Helical Antenna Calculator

Design parameters and performance calculations

Input Parameters
MHz
λ

Rec: 0.2-0.25

Min: 3, Max: ~16

λ

Ideal: 1.0

Physical Dimensions
Wavelength (λ)
0mm
Diameter (D)
0mm
Circumference (C)
0mm
Turn Spacing (S)
0mm
Axial Length (A)
0mm
Pitch Angle (α)
0deg
Conductor
Turn Length
0mm
Total Length
0mm
Wire Diameter
0mm
Ground Plane
0mm
Performance
HPBWest
0deg
BWFNest
0deg
Gainest
0dBi
Impedanceest
0Ω

Performance estimates are theoretical

Beam width, gain, and impedance calculations may vary significantly from real-world performance. Formulas tend to overestimate gain. Ground plane size and environmental factors significantly influence actual results.

Polarization Quick Reference
RHCPClockwise winding (looking down)
LHCPCounter-clockwise winding

Dish feed tip: Use opposite polarization of target signal due to reflection inversion.

Parameter Explanations
Detailed descriptions of input parameters and calculated outputs

Input Parameters

Operating Frequency (F):

Defines the frequency in MHz that the helix should operate at. Helical antennas work best between ~500-3000 MHz. At lower frequencies, cross-dipoles are preferred; at higher frequencies, waveguide feeds become more practical.

Turn Spacing (Sλ):

Vertical spacing between turns expressed in wavelengths. Recommended range is 0.2-0.25, though values as low as 0.1 are used in practice. Lower spacing requires more turns to achieve the same gain.

Number of Turns (n):

Defines gain and beamwidth along with turn spacing. Minimum ~3 turns for proper operation, maximum ~16 turns for practical construction. More turns = higher gain and directivity.

Helix Circumference (Cλ):

Circumference of the imaginary cylinder the helix is wound around, measured between conductor centers. Ideal value is 1.0 wavelength for optimal axial mode operation.

Physical Dimensions

Wavelength (λ):Operating frequency converted to wavelength in millimeters.
Diameter (D):Helix diameter measured between conductor center points.
Turn Spacing (S):Real turn spacing in mm. Critical construction dimension along with diameter.
Axial Length (A):Total helix height. Excludes ground plane, connector, and impedance matching sections.
Pitch Angle (α):Angle at which conductor is wound. Related to turn spacing when circumference = 1λ.

Conductor Specifications

Turn Length:Conductor length for one complete turn.
Total Length:Total conductor needed. Add extra for impedance matching and build tolerances.
Wire Diameter:Ideal conductor diameter. Not critical - thinner wire generally acceptable.
Ground Plane:Minimum diameter for circular ground plane, or side length for square plane.

Performance (Estimated)

HPBW:Half Power Beam Width - angle between -3dB points of main lobe.
BWFN:First Null Beam Width - angle between nulls around main lobe.
Gain:Peak gain in dBi. Formulas tend to overestimate real-world performance.
Impedance:Typically ~140Ω. Use impedance matching to achieve 50Ω for coax connection.