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Yagi Antenna Calculator
Calculators / Yagi Antenna
Yagi-Uda Antenna
Calculator
Calculate reflector length, driver length, director lengths, element spacing, and boom length for a Yagi-Uda antenna. Based on the NBS Technical Note 688 (Viezbicke) optimised tables — the industry standard reference for Yagi design.
Reflector
Driven Element
Directors
⚙ Yagi-Uda Design Engine
λ = — m in free space
Affects element length via d/λ correction
More elements → higher gain, longer boom
Advanced Parameters
mm
Boom correction shortens element lengths
NBS TN-688 Viezbicke optimised design
Folded dipole: use 4:1 balun for 75 Ω coax
Bare metal ≈ 0.95, insulated ≈ 0.85–0.93
Element Dimensions Table
| # | Element | Length | Half-Length | Spacing from Refl. | Position on Boom |
|---|---|---|---|---|---|
| Enter values above to generate table | |||||
Calculated Results
Boom Length
—m
Reflector (Lrefl)—
Driver (Ldrive)—
Director 1—
Last Director—
Free-space λ—
Element spacing—
Estimated Gain—
Front-to-Back Ratio—
3 dB Beamwidth (E)—
Input Impedance—
Number of Elements—
Enter values above to calculate.
📖 Design Theory
A Yagi-Uda antenna uses a single driven element (dipole) plus parasitic elements — one reflector behind the driver and one or more directors in front — to create a highly directive beam.
Reflector Length
Lrefl ≈ 0.5λ × k × 1.05
≈ 5% longer than driven element. Spaced 0.2λ behind driver.
Driven Element
Ldrive = 0.5λ × k × C(d/λ)
Half-wave dipole, shortened by d/λ correction factor C.
Directors
Ldir,n ≈ 0.5λ × k × 0.89–0.93
3–5% shorter than driven element each. Spaced 0.25–0.35λ apart.
Gain scales approximately as +1 dB per added director for well-designed arrays. The NBS TN-688 tables give the globally optimised spacings for each element count.
📡 Radiation Pattern Viewer
Live Simulation
|
◉ Pattern updates with element count
Plane
Elements
5
313
Boom Length
1.5 λ
E-Plane Pattern
3D Beam Pattern
ℹ
Design Insights
Enter frequency and select element count to see live design insights.
Common Applications
Amateur Radio (VHF/UHF)
2 m (144 MHz) and 70 cm (432 MHz) Yagi arrays for weak-signal and EME (moonbounce) work.
TV Aerial Reception
UHF Yagi arrays for DVB-T terrestrial television reception — the most common Yagi application.
Point-to-Point Links
Long-range WiFi (2.4/5 GHz) and ISM-band directional links between buildings.
Satellite Tracking
Cross-Yagi (dual-polarisation) arrays for LEO satellite communication and weather imagery.
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