Antenna Calculator

Lengths, loaded verticals, coils, traps and transformers

Antenna design workbench

Choose a section, enter real construction values and use the drawing beside the result. Calculated lengths are starting dimensions—not guaranteed installed resonance. Cut long, build with adjustment range and finish with an antenna analyser.

Loaded radiators, traps and transformers depend on construction, surroundings, losses and component tolerances. Each section states what its model includes.

Resonant-length starting point

Velocity-factor corrections in these practical factors shorten free-space wavelength. Installed height, conductor diameter, insulation and nearby objects still move resonance.

AntennaFrequency (MHz)

12.59 m total
41.30 ft

Estimated feed-point impedance
Resistance near 50 Ω with substantial capacitive reactance

Correct matching method
Use a series inductor at the feed point to cancel the capacitive reactance, then trim or tap it for a 50 Ω match. Add a 1:1 coax choke.

Starting dimension only. Installed resonance changes with conductor size, height, surroundings and feed arrangement.

Feed-point impedance is an estimate, not a fixed result from length. Measure the installed antenna at its feed point with an analyser before building or adjusting the final matching network.