Dipole Antenna Calculator
This dipole antenna length calculator by following industry standards, calculates dipole length, length of each leg, and adjusted dimensions using formula L = 468/f.
When constructing a ham radio antenna for the 20-meter band (operating at 14 MHz), the antenna calculator would indicate that approximately 33 feet of wire is needed for a half-wave dipole. The calculator accounts for real-world factors like end effects and wire characteristics, which typically result in a physical length about 5% shorter than the theoretical wavelength.
How to Use Dipole Antenna Calculator
- Enter Frequency (MHz): Input your desired operating frequency, i.e. 14.200 for 20-meter amateur band
- Enter Wire Diameter (mm): Enter conductor diameter, Default: 2mm, Common range: 1-4mm
- Enter Velocity Factor: Default: 0.95, Adjustable range: 0.01-1.00
- Height Above Ground: Enter installation height in meters, Default: 10 meters
- The calculator computes the total antenna length, the length of each leg, and adjusted lengths.
Dipole Antenna Length Table
| Frequency (MHz) | Total Length (feet) | Length per Leg (feet) |
|---|---|---|
| 3.5 | 133.7 | 66.8 |
| 7.0 | 66.9 | 33.5 |
| 10.0 | 46.8 | 23.4 |
| 14.0 | 33.4 | 16.7 |
| 18.0 | 26.0 | 13.0 |
| 21.0 | 22.3 | 11.2 |
| 24.0 | 19.5 | 9.8 |
| 28.0 | 16.7 | 8.3 |
| 50.0 | 9.36 | 4.68 |
Dipole Antenna Formula
The equation for calculating dipole length is:
L = 468/fWhere:
- L represents Length in feet
- f represents Frequency in MHz
- 468 is the conversion constant accounting for end effects
Wavelength Calculation:
λ = c/f where:
- λ = wavelength in meters
- c = speed of light (299.792458 m/μs)
- f = frequency in MHz
Dipole Length:
L = (λ/2) × VF where:
- L = total length in meters
- VF = velocity factor (typically 0.95)
Impedance Calculation:
Z = 120(ln(4h/d) - 1) where:
- h = height above ground
- d = wire diameter
Designing an antenna for 7.1 MHz:
L = 468/7.1 = 65.9 feet total length (33 feet per side)For metric calculations, use:
L(meters) = 142.5/f(MHz)How to Calculate Dipole Antenna Length
- Establish the operating frequency
- Apply the standard formula (468/f)
- Include the velocity factor (typically 0.95 for bare wire)
- Determine individual element lengths (total length divided by 2)
Calculating a dipole for 28.4 MHz:
Total Length = 468/28.4 = 16.48 feet
Each element = 16.48/2 = 8.24 feet- 80m Band (3.75 MHz): Length = 468/3.75 = 124.8 feet total, Each element = 62.4 feet
- 40m Band (7.15 MHz): Length = 468/7.15 = 65.45 feet total, Each element = 32.73 feet
- 20m Band (14.175 MHz): Length = 468/14.175 = 33 feet total, Each element = 16.5 feet
- 10m Band (28.85 MHz): Length = 468/28.85 = 16.22 feet total, Each element = 8.11 feet
- 6m Band (50.1 MHz): Length = 468/50.1 = 9.34 feet total, Each element = 4.67 feet
What is a Dipole Antenna?
A dipole antenna is the most fundamental design in radio communications. It features two identical conductive elements mounted horizontally and fed at the center point. The overall length typically equals one-half wavelength at the desired operating frequency.
The radiation pattern of a dipole resembles a figure-8 when viewed from above, making it perfect for directional communication perpendicular to the antenna’s axis.