Presented here is a versatile, durable, and rather unique wifi extender antenna that can greatly increase your wireless networking range and speed. When built with ten or more turns, this helical wifi antenna vastly outperforms the cantennas and wi fi wok tops often seen on the internet. A short five turn helical makes a very good feeder for a wifi parabolic dish antenna. A special quality of this antenna is that it radiates and receives a circularly polarized signal. It does not favor vertically or horizontally polarized signals. Thus, this antenna works well with wifi signals reflecting off of buildings, moving vehicles, or antennas oriented at odd angles. Circularly polarized signals are less affected by rain, so you can reach distant access points in stormy weather. There is a 3 dB loss of gain when using this antenna with linearly polarized signals, but the difference is more than made up by making the antenna long - at least ten turns for stand-alone usage. It absolutely beats everything but a yagi of similar length.
Be aware that if your goal is to get wireless internet from another location and use it indoors, you should instead consider using a wireless bridge. If you want to provde strong wireless internet coverage to an area, but cannot provide a fiber optic or ethernet cable to your wireless router, again consider using a wireless bridge to substitute for the unavailable cable, and connect the bridge to the router.
Design parameters for this helical wifi antenna were calculated using the online helical antenna calculator and was inspired by similar designs used for the AMSAT OSCAR 40 satellite.
At this point you should have a PC board with a circle in the center, four tick marks on the circle at 90 deg intervals, and one tick mark exactly between two others.
Space the turns 2.5 cm on a
tube of 3.9cm outer diameter.
Here is a table used for my prototype helical wifi antenna and its connector. Note that turn 1 starts at 0.8 cm (height above ground plane of feedpoint). Turns Spacing is 2.5 cm, and the diameter is 3.9 cm (close enough for 1.5" PVC tailpiece). If your connector can be trimmed to allow a feed connection closer to the ground plane than 0.8CM, then simply run the helix as low as necessary. Most impartant is keeping the proper spacing between turns.
(fits 1.5" PVC tailpiece)
Height (cm) above
At this point, helical wifi antenna is ready for its smoke test...plug in the cables and look for some signals! Theoretical gain of the prototype helical was about 18 dB over an isotropic radiator; it beat my biquad by about 7 to 13 RSSI units, and indeed seemed less sensitive to polarization and rainfall. Signals still seem to fluctuate much from second to second. If your antenna is functioning satisfactorily at this point, I suggest spray painting three layers of clearcoat onto the windings and groundplane for stability and corrosion prevention.