Flower Pot antenna calculator

About

This calculator gives the length of every part of a Flower Pot coaxial antenna: the upper and lower dipole legs, and the length of cable you need to wind the choke.

The upper leg is the centre conductor, the lower one the braid; below them is a choke wound from the same cable

Operating frequency		MHz
Resonance factor		%
Velocity factor of the cable		-
Result
Wavelength (λ)		cm
Upper leg		cm
Lower leg		cm
Length of the choke cable		cm

Notes:

The resonance factor lies between 5 and 10 %; the default is 7.5 %, the middle of that range.
The cable velocity factor is fixed by the dielectric: 0.66 for solid polyethylene, RG-58 among others, and 0.8 for foamed dielectric.
The number of turns in the choke is not calculated, because it depends on the diameter of the pipe. What is calculated is the length of cable needed to wind it.
Wind clockwise or anticlockwise, it makes no difference, but keep the turns tight against each other. The start and the end of the winding must match the calculated cable length exactly. Wind onto PVC pipe 20–40 mm across.
Important: the pipe must not have a metal screen inside it, or the choke will not work.

How to cite this calculator

UR3PKI. «Flower Pot antenna calculator». CyberDev.Space. https://cyberdev.space/en/radio/calculators/antennas/flower_pot (licence CC BY-NC-SA 4.0).

The licence lets you use this material freely, including in teaching materials, but only with attribution to the author and a link to the source.