Antenna Dipole Calculator

This tool calculates the physical length of a half-wave dipole antenna (total and per-arm), its theoretical feed-point impedance (~73 Ω in free space), and estimates radiation pattern characteristics. It accounts for velocity factor and wire diameter to improve real-world accuracy over idealized formulas.

Use it during antenna prototyping, PCB layout (for printed dipoles), or field-deployed wireless systems (e.g., LoRaWAN, RFID, ISM-band radios). It’s especially helpful when selecting resonant lengths for custom antennas before simulation or measurement.

Velocity Factor represents the reduction in signal propagation speed along a conductor due to insulation and proximity effects — typically 0.95–0.99 for bare wire in air, and ~0.66–0.85 for insulated or coaxial-fed dipoles. Lower VF shortens the required physical length for resonance.

For standard copper wire: 1–3 mm (AWG 12–18); for PCB traces: 0.5–2 mm; for tubing (e.g., aluminum elements): 6–12 mm. Diameter affects bandwidth and impedance slightly — larger diameters yield broader bandwidth and lower Q, but the calculator uses empirical corrections only for moderate ranges.

Because real-world dipoles exhibit end effects—capacitive coupling at tips lowers resonant frequency, requiring physical shortening. The calculator applies a standard ~5% reduction from λ/2 (adjusted by VF and diameter) to achieve resonance at the target frequency.

No — this tool is optimized specifically for standard center-fed, straight-wire half-wave dipoles. Folded dipoles have ~4× higher impedance (~300 Ω), and OCF dipoles require different modeling; use dedicated calculators or EM simulation for those configurations.

The calculator assumes free-space operation and gives a nominal impedance near 73 Ω. Real impedance varies with height above ground, nearby objects, and conductor thickness. Bandwidth is approximated using standard Q-factor relationships — for precise matching, always verify with a VNA or simulator.

Best suited for HF through UHF (3 MHz – 3 GHz). Below 3 MHz, ground losses and size become dominant; above 3 GHz, manufacturing tolerances, skin effect, and parasitic coupling significantly impact performance beyond the scope of this simplified model.

Yes — proximity to conductive surfaces detunes the antenna, usually lowering resonant frequency and distorting the pattern. This calculator assumes ideal free-space conditions. For enclosed or constrained deployments, reduce the initial length by 2–5% and fine-tune empirically or simulate.

A dipole’s balanced 73-Ω feed-point impedance ideally interfaces with a 1:1 current balun to suppress common-mode currents on the feedline. If using coax (unbalanced), a balun is essential — the calculator doesn’t size baluns, but its impedance output helps select appropriate impedance-matching types (e.g., 4:1 for folded dipoles).