// Tools & Reference

📡 Antenna Calculator Suite

Free, comprehensive antenna calculators for amateur radio operators. Enter your operating frequency and get all key dimensions instantly — in both metres and feet. Covers wire antennas, verticals, loops and Yagi arrays.

🔍 Tip: After calculating, click any diagram panel to enlarge it to full screen.

〰️ Half-Wave Dipole — Visual Modelling

The simplest and most effective HF antenna. Two equal legs fed at the centre, each a quarter-wavelength long. Omnidirectional in azimuth with a figure-8 broadside pattern — maximum radiation perpendicular to the wire. Feed with 50Ω or 75Ω coax via a 1:1 balun.

Total length (m) = 143 ÷ f(MHz) × vf  |  Each leg (m) = 71.5 ÷ f(MHz) × vf
Feed impedance ≈ 73Ω in free space  |  at λ/2 height ≈ 50–73Ω
e.g. 14.225 for 20m SSB, 7.1 for 40m
Affects feed impedance and radiation angle
// Results
Antenna Profile & Dimensions
Azimuth Pattern — Top View
Elevation Radiation Pattern
Current Distribution
How the half-wave dipole works

📐 Inverted-V Dipole — Visual Modelling

A dipole with the centre at the top and the ends drooping at an angle — ideal when you have one support. The drooping legs lower the resonant frequency slightly, so a 3–5% shortening factor is applied. Apex angle of 90–120° is optimal for 50Ω match.

Total length (m) = 138 ÷ f(MHz) × vf  (includes ~3.5% droop correction)
Included angle 90–120° → feed impedance ≈ 50Ω  |  narrower angle → lower impedance
e.g. 7.1 for 40m, 14.2 for 20m
Height of centre feedpoint above ground
90–120° recommended — 120° gives ~50Ω
// Results
Antenna Profile & Dimensions
Azimuth Pattern — Top View
Elevation Pattern — Side View
Current Distribution
How the inverted-V works

⭕ Full-Wave Loop — Visual Modelling

A complete wavelength of wire formed into a loop — square, delta or circular. Offers about 2 dBd gain broadside to the loop, lower noise, and works well on harmonics with an ATU. Feed at the bottom for vertical polarisation (DX), feed at the top for horizontal polarisation (NVIS).

Perimeter (m) = 306 ÷ f(MHz) × vf  |  Square side = perimeter ÷ 4
Delta side = perimeter ÷ 3  |  Feed impedance ≈ 100–120Ω — use 4:1 balun
HF bands — loops are most effective on 40m and lower
Height above ground of lowest point of loop
// Results
Wire Profile & Geometry
Elevation Radiation Pattern
Azimuth Pattern — Top View
Current Distribution
How the full-wave loop works

📶 Ground Plane Vertical — Visual Modelling

A quarter-wave vertical with radials forming an artificial ground plane. Omnidirectional at low radiation angles — excellent for DX. Horizontal radials give ~35Ω feed; drooping radials 45° raises it to ~50Ω allowing direct coax connection. More radials = lower ground loss = better efficiency.

Vertical element (m) = 71.5 ÷ f(MHz) × vf  |  Each radial (m) = 73.0 ÷ f(MHz) × vf
Droop 45° → feed impedance ≈ 50Ω direct coax  |  Horizontal → feed impedance ≈ 35Ω — needs matching
Works for any band — HF to UHF
0° = horizontal (~35Ω) · 45° = typical (~50Ω) · 90° = vertical — experiment between 30–50° for best SWR
Base of vertical — affects takeoff angle
// Results
Wire Profile & Geometry
Elevation Radiation Pattern
Azimuth Pattern — Top View
Current Distribution
How the ground plane works

🔱 J-Pole — Visual Modelling

An end-fed half-wave radiator with a quarter-wave matching stub — the "J" shape. No ground radials needed. The stub acts as a transmission line transformer, bringing the high-impedance feed end of the ½λ element down to ~50Ω. Omnidirectional, low takeoff angle — excellent for VHF/UHF base station use.

Radiating element (m) = 143 ÷ f(MHz) × vf  |  Matching stub (m) = 71.5 ÷ f(MHz) × vf
Feed tap from bottom ≈ 5% of stub length  |  Gap between elements = 0.03 × λ (auto-calculated)
e.g. 144.5 for 2m, 433.0 for 70cm, 51.0 for 6m
Affects takeoff angle — higher = lower radiation angle
Optional — override with your actual measured lengths
Leave blank to use calculated value
Enter your actual cut stub length
Your current tap position for tuning
// Results
Wire Profile & Geometry
Elevation Radiation Pattern
Azimuth Pattern — Top View
Current Distribution
How the J-Pole works

🔄 Magnetic Loop — Visual Modelling

A compact, high-Q resonant loop — typically 0.1λ circumference or less. Excellent for restricted spaces and indoor use. Highly directional — figure-8 pattern broadside to the loop, deep nulls off the edges. Sharp tuning (narrow bandwidth). Capacitor voltage is extremely high — handle with great care.

Circumference (m) = π × diameter  |  Inductance = μ₀ × D × (ln(D/d) − 0.774)
Capacitance (pF) = 1 ÷ (4π²f²L)  |  Q = Xl ÷ (Rloss + Rrad)
HF bands 1–30 MHz — mag loops are most practical on 40m and up
Outer conductor diameter — larger loop = higher efficiency
Copper pipe OD — larger conductor = higher Q
Used for capacitor voltage warning — keep power low!
Vertical = figure-8 horizontal pattern · Horizontal = omnidirectional
// Results
Wire Profile & Geometry
Elevation Radiation Pattern
Azimuth Pattern — Top View
Current Distribution
How the magnetic loop works

🔲 Cubical Quad — Visual Modelling

Two full-wave loops — driven element and reflector — spaced ~0.2λ apart on a boom. Typically 1.5–2 dB more gain than a 3-element Yagi for the same boom length. Lower radiation angle and lower noise floor than Yagi. Excellent for 10m, 15m and 20m. Spreaders are typically fibreglass or bamboo.

Driven loop (m) = 306 ÷ f(MHz) × vf  |  Reflector loop (m) = 320 ÷ f(MHz) × vf
Spacing (m) = 0.2 × λ  |  Side = perimeter ÷ 4  |  Feed ≈ 100Ω → 4:1 balun → 50Ω
Most practical on 10m–20m — gets large on lower bands
Height of bottom of quad above ground
// Results
Wire Profile & Geometry
Elevation Radiation Pattern
Azimuth Pattern — Top View
Current Distribution
How the cubical quad works

📡 Yagi-Uda — Visual Modelling

Classic Yagi-Uda directional array — one reflector, one driven element, one to five directors. Highly directional with gain increasing with each added director. Based on W6SAI/ARRL optimised tables. Select element count to recalculate and redraw everything live.

Reflector = 0.495λ  |  Driven = 0.473λ  |  Directors = 0.455λ → 0.429λ
Gain ≈ 7.5–12 dBd (3→7 el)  |  F/B ≈ 20–28 dB  |  Feed ≈ 25Ω — use gamma/T-match
Works for any band — HF to microwave
Height above ground — affects takeoff angle
// Results
Wire Profile & Geometry
Elevation Radiation Pattern
Azimuth Pattern — Top View
Current Distribution
Gain vs Element Count
How the Yagi-Uda array works

📐 Fan Dipole — Visual Modelling

Two input modes — enter what you know. Mode 1: measure ground distances with a tape, get the wire lengths you need. Mode 2: enter your actual wire lengths, get the anchor distances and angle. Both modes show the included angle and radiation pattern.

Vertical height from ground to apex/feedpoint
Measure on ground from mast base to left wire tip anchor
If tied off on a fence post or bracket, enter that height
Bands:
// Results
Wire Profile & Geometry
Elevation Radiation Pattern
Azimuth Pattern — Top View
Current Distribution
How the fan dipole works

〰️ EFHW — Visual Modelling

End-Fed Half Wave modelling with current distribution and radiation pattern. Select your erection style — each produces a different profile diagram, current distribution and elevation pattern.

Erection Style
Ground distance from mast base to 49:1 UNUN
Ground distance from mast base to far wire tip
Full wire from 49:1 UNUN over apex to far end tip
Presets:
// Results
Wire Profile & Geometry
Elevation Radiation Pattern
Azimuth Pattern — Top View
Current Distribution
How the EFHW works

📶 Log Periodic Dipole Array — Visual Modelling

A wideband directional antenna where element lengths and spacings follow a geometric (logarithmic) progression defined by the design ratio τ (tau). Each element covers a portion of the frequency range — the antenna is always active over its entire bandwidth with near-constant gain and impedance. Used extensively in TV antennas and HF wideband arrays.

Design ratio τ = L(n+1) ÷ L(n) = d(n+1) ÷ d(n)  (typically 0.7–0.98)
Longest element = ½λ at lowest frequency  |  Shortest = ½λ at highest frequency
Gain ≈ 7–11 dBd (τ dependent)  |  Feed impedance ≈ 50–200Ω
Longest element resonates at this frequency
Shortest element resonates at this frequency
Higher = more elements, more gain, longer boom
Relative element spacing — 0.1–0.2 typical
// Results
Wire Profile & Geometry
Elevation Radiation Pattern
Azimuth Pattern — Top View
Current Distribution
How the log periodic works

🍳 Parabolic Dish Antenna — Visual Modelling

A reflector antenna using a parabolic surface to focus electromagnetic energy onto a small feed antenna at the focal point. Extremely high gain — gain increases with dish diameter and frequency. Used for satellite, microwave links, EME (moonbounce) and radio astronomy. All reflected rays are parallel to the axis — the parabola focuses a plane wave to a point.

Gain (dBi) = 10 × log₁₀(η × (π × D ÷ λ)²)  (η = efficiency, typically 0.55–0.65)
Beamwidth (°) = 70 × λ ÷ D  |  Focal length = D² ÷ (16 × depth)
e.g. 2400 for 2.4GHz WiFi/ATV, 10368 for 3cm, 1296 for 23cm
Aperture diameter of the reflecting surface
Depth from rim to vertex — determines focal length
0.55–0.65 typical · 0.75+ with precision feed
// Results
Wire Profile & Geometry
Elevation Radiation Pattern
Azimuth Pattern — Top View
Current Distribution
How the parabolic dish works
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