Ham Radio Antenna Length Calculator
Calculate the physical length of dipole, vertical, and loop antennas for any amateur radio frequency, accounting for velocity factor.
Results
What is it?
A resonant antenna's physical length depends on the operating frequency, the fraction of a wavelength required for the antenna type (e.g., λ/2 for a dipole), and the velocity factor of the conductor — the ratio of signal propagation speed in the medium to the speed of light in free space.
How to use
Enter your target frequency in MHz, choose the antenna type, and adjust the velocity factor if needed. The result is the total physical length to cut. For a dipole, divide the result by 2 for each leg.
Example scenario
Building a 2-metre (144 MHz) half-wave dipole from bare copper wire (VF ~0.95): λ = 299.792 / 144 ≈ 2.082 m. Half-wave factor ≈ 0.4839. Total length ≈ 2.082 × 0.4839 × 0.95 ≈ 0.957 m (95.7 cm), so each leg is ~47.8 cm.
Pro tip
Always cut your antenna slightly long (add ~2-3%) and trim toward resonance while checking SWR with an antenna analyser. Velocity factor varies with conductor diameter and insulation; bare wire is closest to 0.95-0.98. Common HF bands: 40 m (7 MHz), 20 m (14 MHz), 10 m (28 MHz). VHF: 2 m (144 MHz), 70 cm (432 MHz).