Parabolic wifi antennas are generally thought of as dish shaped objects, fed by a yagi, biquad or helical radiator at the focal point.These dishes are curved in three dimensions and involve considrable effort to construct from scratch.An alternative is the two dimensional "linear focus" reflector. It focuses energy along a "focal line" instead of one point, and works quite well with simple dipole antennas.Design is as simple as selecting a suitable parabolic curve, plotting it on a flat surface, and fitting a sheet of mesh or solid metal to the parabola.
Doing the design calculations by hand is quite time consuming; there is excellent software enabling one to create a template and in minutes. For doing the calculations, one good parabolic antenna calculator is HDL_ANT. Another very useful calculator, called Parabola, was designed originally for solar cooking, and can be used for making wifi network antennas. When using these, bear in mind that the f/D ratio (focal length /diameter) should be between 0.3 and 0.6 for optimal performance.
This linear focus parabolic wifi antenna consists of a sheet of metal shaped to precisely fit a two dimensional parabolic curve. Gain is about 15 dB over a dipole, and depends greatly on quality of construction.Of greatest importance is shaping the sheet metal to accurately follow the parabolic curve given in the template.Parts may be found at large hardware retailers such as "Home Depot" or local scrap metal dealers.Versions of this antenna have been made using automotive sheet metal; others use wire mesh.Whatever the material: follow the curve!
This antenna can be built in a couple of hours and involves a fair amount of measuring, cutting, bending, and bolting metal.Use caution around the sharp edges when finished, put it up and enjoy a very durable antenna that provides great signals.
Parts & Equipment Required:
A parabolic wifi antenna template,
Another parabolicwifi antenna
Rear view of the linear focus
This antenna can be constructed in a couple of hours and some measuring, cutting, bending, and bolting metal.Use caution around the sharp edges. When finished,put it up and enjoy a very durable wifi antenna that provides long range and high bandwidth connectivity.
Note how "A" and "B" are bolted together.
YOU SHOULD NOW HAVE A PARABOLIC REFLECTOR WITHOUT A MOUNT
YOU SHOULD NOW HAVE A PARABOLIC REFLECTOR that can accommodate a USB wifi adapter along the focal line.Mount the assembled reflector and adapter in a window, on a balcony, or wherever there is a line of sight path to the desired wifi access point.
For best performance, consider using a biquad feed. Other choices include using a colinear dipole, or using a 6" length of PVC to place a USB wifi adapter in front of the reflector.An alternative for systems notneeding huge amounts of gain isthe very simple - and smaller - linear parabolic on binarywolf.com. It enables extended range 802.11 connections better than the dipoles supplied with a lot of equipment.