Tool collection
Antennas
Antenna calculators for wire, vertical, loop and directional designs.
Choosing the right antenna family
Antenna design is where radio calculations meet the physical environment. The image on this page is deliberately a real amateur-radio installation rather than a generic computer sketch: the practical antenna is surrounded by supports, structures and feedline, all of which can influence the final result. The calculators in this section provide starting dimensions for several common antenna families, but the numbers should always be treated as design estimates rather than guaranteed finished dimensions.
Wire antennas such as dipoles, inverted-Vs, OCF dipoles, fan dipoles and random wires are often the easiest place to start. Their calculated lengths are based on wavelength relationships, but conductor diameter, insulation, height above ground, nearby objects and the angle between elements affect resonance. Vertical antennas add another major variable: the ground or radial system becomes part of the RF environment. Loop and magnetic-loop designs introduce their own trade-offs involving circumference, conductor loss, coupling and tuning range. Directional antennas such as Moxons and Yagis depend on element spacing and geometry as well as frequency.
Use the calculator that matches the physical antenna you intend to build. Keep the intended installation geometry in mind while interpreting the result. A dimension that works in free space may need trimming at the actual site. Whenever possible, verify the finished antenna with an analyser at low power and check both resonance and impedance. The goal is not to make the calculator agree with the instrument; the goal is to use the calculation as a sensible first build that can then be measured, adjusted and documented.
Choosing the right antenna calculation
Antenna calculators are most useful when they give you a sound starting dimension and enough context to finish the build. This collection covers common wire, vertical, loop and directional antennas used by radio amateurs. The calculations use simplified electrical models, so the number on the screen should be treated as a construction starting point rather than a guaranteed resonant dimension. Conductor diameter, insulation, mounting height, nearby metal, ground conditions and the feedline can all move the final result. A practical workflow is to calculate, build slightly long, install the antenna in its intended position, measure it with an analyser or SWR bridge, and then trim or adjust it in small steps. Different antenna families also solve different station problems: wire dipoles are straightforward, verticals can be compact, loops can fit difficult sites, and directional arrays trade complexity for useful gain and directivity.
Tools in this collection
Dipole
Free half-wave dipole antenna length calculator for ham radio. Classic 468/f formula with end-effect, metric & imperial results, diagrams and tuning tips.
Inverted V
Inverted-V dipole length calculator. Adjusts for apex angle. Single-support design ideal for limited space.
End Fed
EFHW antenna length calculator with harmonic band coverage. Popular multi-band portable wire antenna.
Ocf Dipole
Off-center-fed dipole calculator. Multi-band wire antenna with 1/3–2/3 or 1/4–3/4 feed split and 4:1 balun.
Random Wire
Recommended random-wire lengths that avoid high-impedance resonances on HF. Includes counterpoise advice, 9:1 unun notes and why certain lengths are safer for multi-band operation with a tuner.
Quarter Wave
¼-wave vertical radiator and radial length calculator for HF and VHF.
Five Eighth
5/8-wave vertical length calculator. Higher gain than ¼-wave with matching notes.
Coil Loaded
Shortened coil-loaded vertical inductance estimator for mobile and portable HF antennas.
Jpole
J-Pole and Slim Jim dimension calculators for VHF/UHF. Separate models for classic J-Pole and Slim Jim with radiator, stub, spacing and feedpoint guidance.
Delta Loop
Full-wave delta loop (equilateral triangle) dimension calculator for HF ham radio.
Full Wave Loop
Full-wave loop (square or rectangular skyloop) perimeter and side calculator.
Moxon
Moxon rectangle (Maxon) antenna dimension calculator. Compact 2-element beam with excellent front-to-back.
Magnetic Loop
Small transmitting magnetic loop estimator for circumference, inductance, resonating capacitance, Q, efficiency and RF voltage. Values are engineering estimates; validate the final design with an antenna model and safe capacitor ratings.
Fan Dipole
Calculate multiple half-wave dipole elements for a fan dipole and show each total and per-leg length.
Ground Plane
Calculate starting quarter-wave radiator and radial dimensions for a ground-plane antenna.
Yagi
Basic 3–7 element Yagi-Uda design calculator. Element lengths and spacing from classic DL6WU / NBS inspired proportions.
Coil Winder
Air-core coil turns calculator (Wheeler formula) and simple toroid turns estimate.