Bi-Quad WiFi Antenna

Published

Introduction: Bi-Quad WiFi Antenna

About: Green, downsized, dropped out, lifehacking, office cubicle refugee

All WiFi users are constantly wanting more powerful signals. In this instructable we demonstrate how to build a simple but power double bi-quad WiFi antenna.

Parts List

A single-sided copper clad PCB sheet - I found a 20x10cm sheet with an incomplete circuit printed on it but not etched. The print was cleaned off with wire wool.

A length of 1mm diameter bare copper wire - I found a length of mains cable and removed the earth wire.

An N-type chassis connector and an N-type to SMA adaptor.

Four nuts and bolts for attaching the N-type chassis connector to the PCB.

Drill, soldering iron, solder, pliers and your favoured nut and bolt tightening tools

Your WiFi adaptor. I use an Alfa awus036h.

For my other projects see - http://www.ecopunk.org.uk/p/projects.html

Step 1: The Antenna

Here we see a close-up of the antenna. A hole has been drilled into the PCB to accept the N-type chassis connector. Note the sheet of plastic. My initial thought was to shied the plate from the antenna but subsequent experiments have shown no change in signal strength so you do not need this plastic shielding.

You can also see the antenna constructed from the 1mm earth wire. You need to bend the wire so that it forms the diamond pattern as in the photo. Each side of the diamonds are 30.5mm. At the crossovers the wire does not touch itself.

One end of the antenna is soldered to the N-type at a height of 15mm from the collector plate. The other end is attached to one of the bolts holding the N-type chassis connector in place.

Step 2: Rear of Collector Plate

Here we see the rear of the collector plate, with the N-type bolted in place. Here is where we screw on the N-type to SMA adaptor.

Step 3: N-type to SMA Adaptor

This is the N-type to SMA adaptor. Most WiFi stick antennas use SMA connectors so you will need to make your bi-quad compatible.

Step 4: Completed Double Bi-Quad WiFi Antenna

Here we see the Alfa Wifi adaptor attached to the bi-quad via the N-type to SMA adaptor.

There was an improvement of signal over my previous cantenna and the supplied stick antenna.

For more of my projects see http://www.ecopunk.org.uk/p/projects.html

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    36 Discussions

    How about a half wave or a full wave biquad. Is it better than the quarter wave one . I have never seen those on the internet.

    Amazing. One question. Can the N connectors be replaced with any other type of connector?

    1 reply

    You can use N or SMA connectors. If you have an SMA cable, it might make sense to use that so you don't need an adapter, but they are more fragile. Remember, you need to connect the back end of the element to the ground plane. You can use a regular screw if the connector doesn't use 4 screws like the one in the picture .

    Don't use other types of connectors because they may not work well at S band (BNC, UHF, RCA etc.).

    One question, do you get better performance from this with a single feed point vs the standard double feed point construction, or are both pretty close?

    Very nice build! Biquads are *awesome* on their own, but the beauty of it is when coupled with an old sat dish you can get 28~32Dbi if done right. So many designs on instructables are terrible. Antennas are an exacting design requiring tight measurement and spacing to perform well at all. Your build shows people here how to do it right! I just got done making a 20 director YAGI beam and this high frequency RF is hard to keep the measurements in tolerance. Most designs in the 2450MHz range has less than 1mm tolerance.

    It all depends on your skills as a constructor, on if you use something like a dish to concentrate the incoming signal and on if you can shield noise out of the signal as much as possible.

    I have since moved on to a Yagi, for which, I will produce an instructable in the future.

    I've been looking at more of these Bi-quad antennas and they seem to be connected to a cable dish, do they need to be connected to one to be able to receive signal or is that just for better signal?

    The dish is for increased signal. You will get an improvement with a standalone bi-quad over the omnidirectional stick antenna.

    HERE is the write up on a 125 mile linkup between Nevada and Utah.  The 125 mile was not amped, but the 143 mile was.

    1 reply

    An interesting read. Anything is possible with the right tools and research.

    Thanks for posting to this Instructable as it has made me want to improve my hardware.

    I have retired my Bi-Quad and started to build a Yagi.

    I don't think you would get much payback for a reflector that much bigger than the bi-quad element.

    You can build bigger collectors with many elements on them and then link the elements together. You will need to do a search for larger bi-quads.

    http://www.youtube.com/watch?v=rBBKSk627BM&feature=related It appears a lengthy range can be acheived.

    http://www.youtube.com/watch?v=rBBKSk627BM&feature=related

    I am in the process of building a single biquad out of a dish 500. I plan to mount the Alfa inside of the dish and USB out it's lower end into the laptop. It stands on a modified tripod guitar stand. It will of course be modified from the instructions (linked)
    http://www.engadget.com/2005/11/15/how-to-build-a-wifi-biquad-dish-antenna/
    A personality on another forum told me that he has achieved 175 miles with his biquad in ideal conditions. Though I expect that to be an overstatement, I still will be expecting to see most of the APs in my small city of 100k people so it should be pretty noisy..
    I am also researching converting everything (including my Alfa) over to type F connections for universality. I understand that 50 ohm is the RF standard so I figure 50 OHM connectors and a very short length of 400 series coax cable will do the trick.
    I will report my findings in a few weeks.
    Peace

    2 replies

    I'd very much like to read your findings so make sure you post a link.

    I think all the long distance connections are set up rather than random finds. In other words the claimer is optimising both ends; maybe a high-power AP (possibly with a dish at that end too) and then searching only for that AP.

    I can get about 40 APs, in my street alone, with my current setup. The number of open and WEP APs is very small. Time to cast the net wider.

    The minimum range I will accept is roughly about 1500 yards, but of course I'd like a few miles of range.

    Your suggestion makes perfect sense regarding both ends being dish equipped. I'd bet that the AP had a unidirectional amplified feed as well, and possibly from a higher elevation to a lower on a fair weathered day.

    I would say that HSPA and WiFi use different frequencies, therefore have different wave lengths.

    The dimensions of the bi-quad antenna are matched to the wave length of WiFi and would not work with HSPA.

    You would have to make an element of different dimensions.

    If you Google "hspa bi-quad" you will find information. Much of it vague and not in English.

    Read the literature on WiFi biquad. Determine why the dimensions are what they are for WiFi and scale to HSPA wave-lengths.