Preface

This calculator helps design a dipole antenna with a lumped-constant loading.

At modest heights (10-30 meters) it will work well if its physical length is longer than 0.2xwavelength. This threshold length is displayed as the "best length". Shorter lengths will be less efficient.

The antenna can be fed directly with 50 ohm coaxial cable. The design is based on the concept of inductive loading, widely used in center loaded mobile whip antennas.

For maximum efficiency, the antenna should be as long as possible, consistent with available space. The loading coils should be as far from the center feed as possible, bearing in mind that the farther the coils are from the feed point the larger they become.

For maximum efficiency, select the longest center-to-coil length and largest inductor that is practical for your application. To design the required coils, see the Air Coil Design calculator.

Antenna Design

The following diagram illustrates the key measurements.

To compute inductance

1. Enter the wire AWG # or diameter.
2. Enter the desired center frequency or wavelength.
3. Describe the antenna.
   • Enter the available space for the dipole.
   • Enter the distance from center to coil, which must be less than half the dipole's overall length.

To try different locations for the load coil.

1. Change the center-to-coil distance, longer is more efficient.