What This Calculator Does
A dipole antenna is simple, useful, and efficient. It works best when its total wire length matches a chosen part of the radio wavelength. This calculator converts frequency into wavelength. It then gives the total dipole length, each leg length, and suggested cut length. The cut length includes extra tail wire for trimming. That helps builders avoid cutting the antenna too short.
Why Corrections Matter
A perfect half wave in free space is only a starting point. Real wire has end effects. Insulation, nearby roofs, trees, masts, and soil can shift resonance. The velocity factor changes the electrical length. The end correction reduces the physical length for common wire dipoles. A trimming allowance adds spare wire at both ends. These settings make the result more practical.
Using The Results
Start with the calculated cut length. Install the antenna at the intended height. Keep the two legs straight when possible. Keep the feed point secure. Then measure resonance with an analyzer or a transmitter and safe meter. If the resonant frequency is too low, shorten both legs equally. If it is too high, lengthen them if spare wire remains. Make small changes and test again.
Good Design Tips
Use strong wire and weatherproof connections. Add strain relief near the center insulator. Keep the feed line at a right angle for several feet. This can reduce pattern distortion. A balun or choke can reduce feed line current. The calculator does not replace field tuning, but it gives a strong starting point. It also supports different units, so results are easy to cut.
Physics Behind It
Radio waves travel near the speed of light. Frequency and wavelength are linked. Higher frequency means shorter wavelength. Lower frequency means longer wavelength. A half wave dipole uses about one half of that wavelength as its active radiator. Each side is one quarter wavelength. Small correction factors turn the ideal physics value into a usable workshop length.
For best accuracy, enter the frequency in the same mode used by your radio. Use megahertz for most amateur bands. Use kilohertz for lower frequency work. Record each measurement after trimming. Good notes make later repairs and band changes much easier. They also prevent repeated mistakes.