Easy to Build WIFI 2.4GHz Yagi Antenna

This antenna will extend the range of your WiFi or 2.4GHz devices (like surveillance cameras) into many miles and kilometers. A yagi antenna is basically a telescope for radio waves. I tired the pringle can antenna and the Yagi beats it hands down in performance.

Step 1 What You Need

This is an absolutely easy project.

You need an ink jet printer/ Computer
Popsicle sticks
White glue
Crazy glue
Big paper clips (you could use any stiff solid metal wire instead)
USB WIFI, preferably with an antenna extension OR a 2.4 GHz device
soldering iron and lead
Sanding papers
Scissors
Pliers or preferably a nibbler (see photo below, available at radio shack)
a metric ruler with millimeters or a metric caliper.

Comments

[dbartley]

Anyone with experience of reflections from the coax itself? I built a 4-element vertically polarized 850-MHz Yagi antenna. With the coax dangling haphazardly from the boom behind, there seemed to be tremendous problems. These problems seem to disappear by looping the coax behind from boom to the mast, forming ROUGHLY another half reflector.

[dbartley]

The ARRL Antenna Book (Chapter 27, 1991) describes this problem of antenna currents on the transmission lines somewhat. The outside of the coax is actually part of the antenna, being directly attached to an active antenna element, though it is perpendicular in this region. But also its metal further back interacts inductively with other antenna elements in its vicinity. Directing the coax back along the boom, with a large loop (about 1.5 wavelengths) behind and down to the wooden mast improves reception consistency somewhat, rather than haphazard arrangement. But the ideal loop seems to be obtained from the tightest possible. Because of the peculiar geometry and the lack of actual measurement rather than qualitative evaluation, it's hard to understand why this is.

[jbaker22]

Is there a way I can make this wok without taking my router apart. I like it's warranty.

[Biotele]

you can use a 2.4 GHZ coax cable with adapter hooked to your router.

[jbaker22]

No i just have ethernet cables plug. Will taking aluminum foil and attaching it to the antenna work?

[Biotele]

get a solid piece of copper wire that fits into the router's antenna socket, and connect to one side of the dipole. The wire should short.

[frankortega]

I found a company and there antenna are not too expensive, I try to build
two type of antenna in (easybuild2.4 GHz), but still lacking some imformation, and its end up lossing my time, need more information,kind ofcable,connector,and how long
the maximum leght of the cable.
thanks

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2.4GHz (Wi-Fi Antenna)
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[Biotele]

I don't understand your question. You build this antenna but you can't connect it to the usn wifi receiver? Can you post a picture of what you build so far? Thanks.

[frisbeechamp1983]

If I added like a reflector to the back to send all waves forward, the put it on a slow rotation like radar, would it still work? It would be attached to a modem in my basement,the wired to the roof of my house.

[andrew101]

actually if you look at yagi antenna theory, the wire just behind the driven wire acts like a reflector If you added a dish behind the antenna, and the spacing was wrong, you would cause undue interference for yourself, and chances are it would work against you.

a possibility would be to add something covering the back that was grounded, it would act as a shield to interference, and not a reflector though.

[Biotele]

Yes that will work. Can you post a picture that sounds like a great idea.

[khan0daulatzai]

guy can any paste a video of this test,,,plzz

[Computothought]

Made your antenna, but have not tested it yet. have to rescue a cable first.

[Biotele]

you don't need a cable a tiny short wire between the active strip on the board and one side of the loop will work. Photo's please. thanks

[andythemac]

Excellent instructable! I've built the antenna but don't know where to solder the co-axial to my DWL-G122 adapter.
Here's some pics of both sides:

[Biotele]

Check out this site:

http://www.sohtell.se/DWL-G122/

this one is better if you want to solder a coax directly:

http://usb-wifi.blogspot.com/2009/12/usb-wifi-dlink-dwl-g122-modification.html

[jzhan]

here's the image

[Biotele]

Excellent. The top one.

[jzhan]

For the driven element, do you cut the clip twice (as in cutting the clip into two separate pieces). Or do you just cut it once, and leave it still as one connected element?

[Biotele]

Once and leave as one connected element. You cut it at the middle were one side ends so that you end up with a loop with ends that are almost touching each other (about 1 or 2 mm gap).

[jzhan]

suppose this is the driven element, how do you cut it?

[schkip1973]

it would be great if you ould plot the polar performance of your antenna, even if it were on a 'number of bars of wifi-vs angle' scale'. Even if your antenna wasn't really working well you could probably pick up a Wifi signal 2 miles from home.

Perhaps you can try using a protractor and creating a graph of the angle of the antenna vs. the number of bars you are recieving for a known connection or RSSI.

Thanks for doing the calculations on 2.4G Yagi though!

[leighklotz]

I built a system for making antenna patterns for 802.11 antennas using a WRT54G and a Picaxe. You could use an Arduino or a dedicated stepper controller as well, or a rotation sensor and a DC direct motor.

See here:

http://wa5znu.org/2010/11/pattern/

There's also a video if it in operation.

[schkip1973]

that is awesome dude! that would make a nice 'ible.
is that measurement in a field or paddock, or were you able to remove reflections via other means.

[Biotele]

This is so cool. Can you replace the corner reflect with this antenna and trace the antenna pattern? That will be so awesome!

[Fred82664]

Ubuntu Linux has free software in its repository that you can get. I dose the plotting and much of the calculations. listed in Ubuntu's Snapic program manager under the Armature Radio sub listing.

[Biotele]

I will try to do that. I am very poor in antenna theory. I didn't do the calculations, I used a Java program that I found on the web. Can you explain me why connecting a coax to both sides of the driven element did not work, but connecting one single wire did?

[Dr_Stupid]

because that's kind of like hooking up the + and - wires on your car to one pole of the battery.

You do that, and you're only using the one element and the space in between the conductors as the antenna.

[Wazzupdoc]

It's really not at all like that. The shield and the core of the coax carry complementary parts of the RF electrical and electromagnetic waves. Hooking the shield to the middle of the clip and the core to the end of the clip creates a dipole antenna. The 2011 ARRL Handbook of Radio Communications has some excellent explanations of the theory and practice of using antennae such as these.

[petercd]

Try connecting the center of the coax to the driven element and the sheath/ braided outer conductor to the backplane/ 1st element.
In addition, solder the wire in the middle of the driven element close to the point it enters the pop stick, opposite to where you have it now and not on the ends.

However as abarrow mentioned these antennae are very impedance sensitive and need to be matched for max output.

[abarrow]

The loop driven element presents a different impedance to the transmitter than a simple dipole. Impedance of a dipole is around 70 ohms, while impedance of a loop might be something like 300 ohms. The antenna impedance needs to match the impedance that the transmitter was designed for, or you will get a mismatch and a lot of your power will reflect back into the transmitter. It could be that your particular wifi transceiver wasn't designed for the impedance that a loop presents. You also may not have done a good job of cutting off the internal antenna in your wifi dongle, which will also give you an impedance problem.

You might try replacing the loop driven element with a dipole (the same overall length, but just a single wire with a break in the middle). Just solder the center conductor of your coax to one side, the shield to the other.

[6Talons]

Folded dipole is okay: the Z is not 300 in a yagi --> Z goes way down because of other elements. For dipole, you have to make gamma matcher for 2.4 gigs!

Original explanation on http://www.ab9il.net/wlan-projects/wifi6.html says it!

[6Talons]

The electromagnetic fields about the parasitic elements cause a higher current / lower impedance in the driven element. Here is a page about feeding yagis.

The ab9il.net wifi yagi antenna is one of countless types using a folded dipole.  Commonly used in the microwave antenna industry.

[Biotele]

Ab9il does not use a gamma matcher. He solder both ends of the dipole loop to the coax, something which I found not to work. I just drive it from one end. I didn't find an explanation on the webpage. Can you explain it?

[Fitzwrench]

There's a step by step video of the original antenna being made at http://youtu.be/AEkyDVlfhnw

Been there since 2009, before Biotele copied that wi fi web page

http://www.ab9il.net/wlan-projects/wifi6.html

He doesn't leave anything out, and definitely uses the folded dipole driven element.

[Biotele]

Do you have a hard time telling the difference between popscile sticks and a balsa wood beam? Have you read this instructable? The video is nothing like this instructable. Where are the paper clips? Where is the scaled template to glue the paper clips on?

"He doesn't leave anything out, and definitely uses the folded dipole driven element."
If you read step 7, soldering the both end of the coax to the folded dipole, the way AB9IL did, DOES NOT WORK! I drive it with just one end soldered, the other end in not grounded.

Your accusations are groundless. Please stop commenting.

[schkip1973]

great analysis abarrow. I wish i could hit 'like' for your response. well thought through.
given the narrow bandwidth of the wifi signal he may be able to do a reactive balun / impedance match to the 'folded dipole' section of the antenna over a small frequency range.

[Biotele]

I am going to try building a dipole out of the coax. Thanks for the tip.

[static]

I as well noticed you used a folded dipole. A folded dipole has an impedance of 300 ohms. The impedance mismatch may be why your initial use of coax didn't work well.The simple dipole that aborrow recommend energy matches coax well.

A good instructable. Too bad some don't understand if you create your own images, it doesn't matter if a similar image is already on another million pages. Most basic antenna designs are common knowledge, and can't be copyrighted.

[Biotele]

Thanks. It is easy to accuse of plagiarism. I just happened to use the same program (which is GNU) as other yagi enthusiasts. It is just jealousy.