Calculators for various antenna designs.


RF Antenna calculators for various antenna designs

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Radio waves behave very similar to the photons in light waves. The wavelength calculators used to calculate the antenna element dimensions will therefore use the speed of light (299792458 meters per second) in a vacuum as constant. Note: when using coax for antenna elements it is advised you lookup and apply the velocity factor because RF slows down in coax and this will impact the effective measurements for antenna elements.

J-Pole Antenna Calculator

J Pole Antenna Design

An omni-directional end-fed half-wave antenna with a quarter-wave transmission line matching stub. Invented by the Germans for use on their zeppelins, this antenna is also referred to as a Zepp antenna. In 1936 this design was modified into the current configuration used today and became popular with amateur radio operators by 1943.

Slim Jim Antenna Calculator

Slim Jim Antenna Design

A variation of the J-Pole antenna invented by Fred Judd (UK). An omni-directional folded dipole with a quarter-wave j type matching stud. It gets its name from its Slim constructions and J Integrated Matching.

Quarter Wave Antenna Calculator

1/4 Wave Antenna Design

This is a design is called a monopole antenna. Invented in 1895 by Guglielmo Marconi (IT) who discovered that if he attached the live terminal of his transmitter to a wire perpendicular to the earth and the other terminal was attached to earth, he could transmit for long distances.

It is made of a straight rod conductive material mounted perpendicular to other conductive material or surface that is referred to a the ground plane.

As the dipole antennas, the monopole antennas are also omni-directional, this means they transmit and receive equally well in a 360 degree plane around their axis.

The antenna calculator assumes the antenna will be mounted on a mast, and not be close to actual ground. Hence the addition of ground plane elements.

Coax Collinear Antenna Calculator

Coaxial Collinear Antenna Design

The coaxial collinear antenna is made from two or more sections of coax cut to length for a specific frequency and connected to each outer in an 'out of phase' manner ending with a quarter-wave matching stub. The elements can be quarter-wave or half-wave. I have found that half-wave elements, not more than eight, give the best result. Strangely enough this operates without a ground-plane.

Collinear Dipole Antenna Calculator

Collinear Dipole Antenna Design

The collinear dipole, unlike the coaxial dipole requires a ground-plane to operate. A dual element collinear dipole gave me the same results as an eight element coax collinear. Although this design is not ideal for a 'pipe antenna' it is ideal for mounting in any antenna mast.