Long Range Parabolic Wi-fi Antenna

Part 1: Building the feeder - an Innovative Helical Wi-Fi Antenna

THIS INEXPENSIVE PARABOLIC WI-FI ANTENNA OUTPERFORMS ALL OTHERS!

Presented here is the ultimate long range parabolic wi-fi antenna, in two phases of construvtion. First is the helical feeder, which will be mounted at the dish focal point. When made with ten or more turns, it makes a great stand-alone wi-fi antenna. When a short five turn wi-fi helix is mounted at the focus of a common satellite TV reflector, it delivers excellent long range performance.

Phase two of the project is all about converting common satellite TV antennas into high performance wi-fi dish antennas. If you intend to use multi kilometer wi-fi connections, this is the antenna type to use. A large 2 or 3 meter diameter wi-fi dish can provide 802.11 connections to access points dozens of kilometers away. Satellite - to - wi-fi dish antennas are also easy to convert, requiring replcement of the satellite TV feedhorn with a modest antenna for 802.11 networking. None of the manual "curve making" of scratch built parabolics is necessary.

Obtain a parabolic reflector designed for Ku band direct-to-home satellite service. These are now inexpensive and abundant. The wi-fi dish pictured above was built from satellite TV gear discarded by a local resident. Similar reflectors can be found in thrift stores, flea markets, and other habitats of electronic scroungers. Seek moderate to large reflectors (at least 76cm or 30" diameter), since these will provide greater gain and directivity. We will make a feeder to mount at the reflector focal point.

A helical feed is quite suitable for this wi-fi dish project as it is simple to build, inexpensive, and provides good gain and directivity. Being circularly polarized, a helical eliminates sensitivity to antenna orientation, and performs well when there is rainfall along the signal path. Though there is a 3 dB loss when connecting to linearly polarized access points or clients, gain is restored by using a design with more turns. Note that when circular polarization is to be used on BOTH ends of the link, polarization senses MUST match. Right hand with right hand or left with left. Bear in mind that polarization reverses in a parabilic reflector. Therefore, use a left handed helix if you use a parabolic reflector and want a right hand circular polarized signal.

PARTS REQUIRED FOR THE WIFI HELICAL ANTENNA:

1. one square piece of single sided copper clad PC board for a ground plane
2. one PVC kitchen drain tailpiece (3.8 cm / 1.5"diameter) to hold the helical windings
3. six 1/8" plastic cable ties
4. a length of copper circuit tape (adhesive backed, width 3mm or 1/8") or #14 copper wire
5. one suitable chassis connector (I used a reverse sma type matching the connector on my adaptor)
6. one 90 degree angle bracket with screws and bolts to fit

CONSTRUCTION:

1. Center the tailpiece on the PC board, copper side, and mark the circumference in ink.
2. Mark four locations on the circumference, spaced 90 degrees, where the cable ties will hold down the PVC tube.
3. Mark one location on the circumference, exactly between two 90 degree markings, where the coaxial connector will be mounted.

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.

4. Drill 1/8" holes on the inside and outside of the circumference at the cable tie locations.
5. Drill a hole directly on the circumference suitable for the chassis connector. Carefully measure and drill other holes for this connector if necessary.
6. Drill four holes, spaced 90 deg apart near the bottom end of the PVC tailpiece.
7. Drill holes to accomodate a small 90 degree corner bracket.
8. Drill holes on opposite side of board to accomodate USB wi-fi adapter that will be affixed with cable ties.
9. Tin the copper around the connector mounting hole, then mount the connector. Clip the center pin to keep it only long enough for connection to the helix windings.
10. Cut out a notch to accomodate the connector; it should clear center conductor, but avoud cutting out excess PVC material.
11. Feed cable ties through from the back side of the board, through holes in the tube, and back through the board. Tighten the cable ties, making sure the tube is firmly held to the copper ground plane.
12. Use a ruler and the edge of a sheet of paper to create a template for positioning the windings on the PVC tube. Distance zero represents the ground plane, then add the feedpoint distance, then ticks matching the turns spacing. Use the template to mark your tube on both the feedpoint side and the opposite side. Design parameters for helical wi-fi antennas can be calculated here.
    
    The objective is to precisely wind the helical wi-fi antenna using an accurate guide...

Space the turns 2.5 cm on a
tube of 3.9cm outer diameter.

Go now to Part 2: Setting Up the Wi-Fi Feeder and Parabolic Reflector