Yagi Antenna Calculator

What Is a Yagi Antenna? A Yagi-Uda antenna is a directional beam antenna with multiple parallel dipole elements. Invented by Shintaro Uda and Hidetsugu Yagi (Japan, Tohoku University, 1926). One driven element (fed), one reflector behind it, and one or more directors in front. Gain increases with more elements — each director adds ~1.5–2 dB.

Element Types Reflector: slightly longer than driven element (about 5% longer). Positioned behind. Driven element: half-wave dipole fed by coax (via matching network). Center of the array. Directors: slightly shorter than driven element (about 5% shorter). Multiple directors increase gain. Typical spacing: 0.1–0.25 λ between elements.

Classic Yagi Design Rules (Long-Yagi by DL6WU / ARRL) Driven element length: L = 143/f (meters) where f is frequency in MHz Reflector: 5% longer than driven element Director 1: about 5% shorter Each additional director: slightly shorter than the previous Boom length: 0.4–0.5 λ for 3-element; grows with more elements

Gain vs Number of Elements 3-element Yagi: ~7–8 dBd (over dipole) 4-element: ~8–9 dBd 5-element: ~9–10 dBd 10-element: ~13–14 dBd Each doubling of boom length adds ~3 dB.

Common Amateur Radio Bands 2m (144 MHz): λ ≈ 2.08 m | 70cm (432 MHz): λ ≈ 0.69 m 10m (28 MHz): λ ≈ 10.7 m | 6m (50 MHz): λ ≈ 6.0 m 20m (14 MHz): λ ≈ 21.4 m (Yagi large; often rotatable beam antennas)