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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.
Get "10 RF Design Principles Every Engineer Should Know" Free
Learn practical principles for better RF circuits, PCB layouts, simulations, measurements, and troubleshooting.