Dipole Antenna Calculator
Calculate the optimal wire length for your dipole antenna. Supports horizontal dipoles and inverted vee configurations across all amateur radio bands.
What is a Dipole Antenna?
The dipole antenna is one of the most popular and effective antennas in amateur radio. It consists of two equal-length wire elements fed at the center, creating a simple yet highly efficient radiator. The classic “half-wave dipole” is approximately half a wavelength long at the operating frequency.
Horizontal Dipole
The traditional configuration where the antenna is strung horizontally between two supports. Provides excellent DX (long-distance) performance with low-angle radiation. Best results are achieved when installed at least 1/2 wavelength above ground.
Inverted Vee
A popular variant where the feedpoint is at the top of a single support and the wires slope downward. Easier to install than a horizontal dipole and requires less space. The inverted vee provides good omnidirectional coverage, making it ideal for general operating and contesting.
Key Advantages
- Simple construction with minimal materials (wire, insulators, feedline)
- Efficient radiation with good gain (2.15 dBi in free space)
- Self-resonant design requiring no tuner on the design frequency
- Relatively quiet reception compared to vertical antennas
- Versatile - works well for both DX and local communications
- Low cost and easy to repair or modify
Dipole Antenna Length Formula
The classic dipole antenna formula (also known as the 468 formula) calculates the approximate length:
Length (feet) = 468 / Frequency (MHz)Length (meters) = 143 / Frequency (MHz)Each side = Total Length / 2However, the 468 formula is a simplified approximation. Our antenna length calculator applies end-effect corrections based on wire diameter, configuration adjustments for inverted vees (typically 2-5% shorter), and height considerations for more accurate results. For precise tuning, always start 2-3% longer than calculated.
14.2 MHz = 14200 kHz
Horizontal dipoles provide optimal radiation pattern. Inverted vee requires only one tall support and is easier to install.
Copper is the most common choice. Aluminum is lighter but requires thicker wire. Copperweld combines strength and conductivity.
Common Wire Sizes:
- AWG 24: 0.511mm (lightweight, portable)
- AWG 18: 1.024mm (light duty)
- AWG 14: 1.628mm (standard dipole wire)
- AWG 12: 2.053mm (heavy duty, wider bandwidth)
Adjust the design parameters to see calculation results.
Horizontal Dipole Configuration: The antenna is suspended horizontally between two supports. The feedpoint is in the center. This configuration provides the best radiation pattern for DX communication.
Charts will appear after calculation.
Important Disclaimer
Calculation Accuracy: The lengths calculated by this tool are based on well-established formulas from amateur radio references including 66pacific, M0UKD, and the ARRL Antenna Book. However, these are theoretical values and should be considered starting points.
Real-World Variations: Actual resonant frequency and SWR will be affected by many factors including:
- Wire type and insulation (affects velocity factor)
- Height above ground and ground conductivity
- Nearby conductive objects (buildings, trees, other antennas)
- Feedline type, length, and balun characteristics
- Center insulator and end insulator design
- Environmental conditions (wet vs dry weather)
Best Practice: Always cut the antenna wire 2-3% longer than the calculated length. Install the antenna and measure the SWR with an antenna analyzer or SWR meter. Trim small amounts from each end until the SWR is acceptable at your desired operating frequency. Remember: you can always make it shorter, but you cannot make it longer!
Safety: Ensure all antennas are installed at a safe height and distance from power lines. Use proper RF safety practices. Dipoles carry high RF voltages at the ends when transmitting.
This calculator is provided for educational purposes. The author assumes no responsibility for antenna performance or construction issues. Always verify calculations and follow local regulations.
Tuning Your Dipole Antenna
Even with precise calculations, every dipole needs fine-tuning after installation. Here is the recommended process:
- Start Long: Cut the wire 2-3% longer than the calculated length. It is much easier to trim wire than to add length.
- Initial Installation: Install the antenna at the planned height with proper insulators and feedline. Ensure the antenna is as straight and level as possible.
- Measure SWR: Using an antenna analyzer or SWR meter, measure the SWR across your intended operating frequency range. Note the frequency of minimum SWR.
- Adjust Length: If the minimum SWR is below your desired frequency, the antenna is too long - shorten it. If the minimum is above your frequency, the antenna is too short (you will need to lower the operating frequency or use a tuner).
- Trim Carefully: Remove small amounts (5-10cm or 2-4 inches) from each end of the antenna, maintaining symmetry. Shortening the antenna raises the resonant frequency.
- Re-measure and Repeat: After each trim, re-measure the SWR. Continue trimming in small increments until the SWR is 1.5:1 or better at your desired frequency.
- Document Settings: Once tuned, record the final length, height, and SWR measurements for future reference.
Pro Tips:
- Use a 1:1 current balun at the feedpoint to reduce common-mode currents
- Seal all connections and insulators to prevent water ingress
- Allow the antenna to “settle” for a day before final tuning ( wire stretches slightly)
- Keep the feedline away from the antenna elements to avoid coupling
- Tune during dry weather for most consistent results
Related Resources
References:
- 66pacific Dipole Calculator
- M0UKD Dipole Calculator
- ARRL Antenna Book (Chapter on Wire Antennas)
- FCC Part 97 - Amateur Radio Service Regulations (antenna height limits)