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Guides
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- Beyond Analytical Formulas: Accurate Coil Inductance Calculation with AN-SOF
- Complete Workflow: Modeling, Feeding, and Tuning a 20m Band Dipole Antenna
- DIY Helix High Gain Directional Antenna: From Simulation to 3D Printing
- Evaluating EMF Compliance - Part 1: A Guide to Far-Field RF Exposure Assessments
- Design Guidelines for Skeleton Slot Antennas: A Simulation-Driven Approach
- Simplified Modeling for Microstrip Antennas on Ungrounded Dielectric Substrates: Accuracy Meets Simplicity
- Fast Modeling of a Monopole Supported by a Broadcast Tower
- Linking Log-Periodic Antenna Elements Using Transmission Lines
- Wave Matching Coefficient: Defining the Practical Near-Far Field Boundary
- AN-SOF Mastery: Adding Elevated Radials Quickly
- Enhancing Antenna Design: Project Merging in AN-SOF
- On the Modeling of Radio Masts
- The Equivalent Circuit of a Balun
- AN-SOF Antenna Simulation Best Practices: Checking and Correcting Model Errors
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- AN-SOF 9: Taking Antenna Design Further with New Feeder and Tuner Calculators
- AN-SOF Antenna Simulation Software - Version 8.90 Release Notes
- AN-SOF 8.70: Enhancing Your Antenna Design Journey
- Introducing AN-SOF 8.50: Enhanced Antenna Design & Simulation Software
- Get Ready for the Next Level of Antenna Design: AN-SOF 8.50 is Coming Soon!
- Explore the Cutting-Edge World of AN-SOF Antenna Simulation Software!
- Upgrade to AN-SOF 8.20 - Unleash Your Potential
- AN-SOF 8: Elevating Antenna Simulation to the Next Level
- New Release: AN-SOF 7.90
- AN-SOF 7.80 is ready!
- New AN-SOF User Guide
- New Release: AN-SOF 7.50
- AN-SOF 7.20 is ready!
- New Release :: AN-SOF 7.10 ::
- AN-SOF 7.0 is Here!
- New Release :: AN-SOF 6.40 ::
- New Release :: AN-SOF 6.20 ::
- Show All Articles (2) Collapse Articles
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Models
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- Download Examples
- Modeling a Center-Fed Cylindrical Antenna with AN-SOF
- Yagi-Uda Array
- Monopole Over Real Ground
- Helix Antenna in Axial Mode
- Modeling a Circular Loop Antenna in AN-SOF: A Step-by-Step Guide
- A Transmission Line
- An RLC Circuit
- Explore 5 Antenna Models with Less Than 50 Segments in AN-SOF Trial Version
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- Modeling a Super J-Pole: A Look Inside a 5-Element Collinear Antenna
- Simulating the Ingenious Multiband Omnidirectional Dipole Antenna Design
- The Loop on Ground (LoG): A Compact Receiving Antenna with Directional Capabilities
- Precision Simulations with AN-SOF for Magnetic Loop Antennas
- Advantages of AN-SOF for Simulating 433 MHz Spring Helical Antennas for ISM & LoRa Applications
- Radio Mast Above Wire Screen
- Square Loop Antenna
- Receiving Loop Antenna
- Monopole Above Earth Ground
- Top-Loaded Short Monopole
- Half-Wave Dipole
- Folded Dipole
- Dipole Antenna
- The 5-in-1 J-Pole Antenna Solution for Multiband Communications
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- The Lazy-H Antenna: A 10-Meter Band Design Guide
- Extended Double Zepp (EDZ): A Phased Array Solution for Directional Antenna Applications
- Transmission Line Feeding for Antennas: The Four-Square Array
- Log-Periodic Christmas Tree
- Enhancing VHF Performance: The Dual Reflector Moxon Antenna for 145 MHz
- Building a Compact High-Performance UHF Array with AN-SOF: A 4-Element Biquad Design
- Building a Beam: Modeling a 5-Element 2m Band Quad Array
- Broadside Dipole Array
- Log-Periodic Dipole Array
- Broadband Directional Antenna
- A Closer Look at the HF Skeleton Slot Antenna
- The 17m Band 2-Element Delta Loop Beam: A Compact, High-Gain Antenna for DX Enthusiasts
- Enhancing Satellite Links: The Moxon-Yagi Dual Band VHF/UHF Antenna
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Validation
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- Simple Dual Band Vertical Dipole for the 2m and 70cm Bands
- Linear Antenna Theory: Historical Approximations and Numerical Validation
- Validating Panel RBS Antenna with Dipole Radiators against IEC 62232
- Directivity of V Antennas
- Enhanced Methodology for Monopoles Above Radial Wire Ground Screens
- Dipole Gain and Radiation Resistance
- Convergence of the Dipole Input Impedance
- Impedance of Cylindrical Antennas
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Gain of Helix in Normal Mode
Helical Geometry
The current distribution in a helical antenna of arbitrary size cannot be described in terms of simple series or elementary functions, so most of the available data has been obtained experimentally. The helical antenna was invented by Prof. John Krauss who has investigated its performance as a function of geometry extensively. Refer to “Antennas” by John D. Krauss, 2nd Edition, McGraw-Hill, 1988.
The helix has basically two modes of operation,
- The normal mode or broadside mode where the maximum radiation occurs in the plane normal to the helix axis.
- The axial mode or end-fire mode where the maximum radiation occurs along the helix axis.
The normal mode is obtained in helices that are small compared to the wavelength, therefore their behavior is similar to that of a small loop > with the same number of turns as the helix and with a uniform current distribution. This can be considered as a limiting case and the simulation results can be compared with theory. When the helix size is comparable to the wavelength, the current distribution can no longer be considered uniform and the simulation results will be only compared with measurements.
The helix geometry is usually described in terms of its circumference normalized to the wavelength, C/λ (C = 2πR, R being the helix radius), number of turns, N, and pitch angle, α, defined as
![](https://antennasimulator.com/wp-content/uploads/2022/10/Eq-helix1.png)
S being the pitch or spacing between turns. The starting point and the axis direction of the helix can also be set in AN-SOF, as Fig. 1 shows.
![](https://antennasimulator.com/wp-content/uploads/2022/10/Fig5-20.png)
In the simulations that follow the helix axis will be the z-axis. Also, a ground plane will be placed at z = 0, so the starting point of the helix will be (0,0,Zs), with Zs being small compared to the wavelength. The helix will be connected to the ground plane by means of a short wire having one segment, where a voltage source will be placed.
Normal Mode
For the normal mode of operation, an small helix having a circumference C/λ = 0.01, 5 turns and a variable pitch will be simulated. The pitch varies between 0.001λ and 0.01λ. For these small dimensions, the theoretical prediction is that the radiation pattern must be doughnut-shaped as that of a small loop, with a null along the helix axis. Moreover, the gain in the presence of a perfect ground plane must be 3 (dimensionless) or 4.77 dBi.
Fig. 2 shows the computed 3D radiation patterns of the small helix for a pitch of 0.001λ (left) and 0.01λ (right). It can be seen that the results correspond to the theoretical predictions. The small departure from 4.77 dBi obtained for the largest pitch must be interpreted as a deviation from the theoretical limiting case of an infinitely small helix. This behavior can be appreciated if we plot the peak gain as a function of the pitch, as in Fig. 3, where we can see that the computed gain tends to 4.77 dBi as the pitch tends to zero.
![](https://antennasimulator.com/wp-content/uploads/2022/10/Fig-helix1.png)
![](https://antennasimulator.com/wp-content/uploads/2022/10/Fig-helix2.png)
This result demonstrates the ability of AN-SOF to simulate curved structures with a small size compared to the wavelength.