Easy to Build WIFI 2.4GHz Yagi Antenna

Intro: 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.

STEP 2: Building Overview

The building steps are simple:

1. Print out the scaled Yagi antenna template* (download from next step).
2. Trim paper clips to size and glue them to the template.
3. Use Popsicle sticks to build the antenna's backbone and hold it together.
4. Connect the USB device to the antenna.

*I used a Yagi modeler java applet to generate the diagram. This modeler applet is found on many websites (google "yagi modeler") and its owner is W9CF.

The modeler gives a diagram and the elements' lengths and position. I carefully scaled the diagram and turned it into a template in order to make the building process easy.

You can visit AB9IL awesome website  to get more details on using the modeler for this 15 element Yagi and other fine antenna projects, such as a 20 element WIFI Yagi .

STEP 3: Printing the Yagi Diagram

The most essential point in printing the template is getting the correct scale. In the attached zip file below, are three png picture files.

The antenna is longer than an Letter sized or A4 sized paper. So you have to print the template in two parts (labeled part1 and part2 in the zip file). I have also included the full sized unsplit template if your printer can handle large enough paper.

PRINTING:

Make sure to set your printer's properties to ORIGINAL SIZE (not "best fit to page" ect..).

Set the print orientation to LANDSCAPE.

VERIFYING SCALE:

Use a ruler or caliper to measure if the print is of correct scale. You will notice vertical bars crossing the horizontal line. The vertical bars represent the Yagi "elements" which will be made from paperclips. The horizontal line is the backbone of the antenna which will be build out of popsicle sticks.

You will also notice numbers next to the elements. These numbers are in pairs. The first number is the length of the element in millimeters. The second number, is the distance from the start of the diagram to the element, in millimeters.

Measure the size and position of a couple of elements on each prints. If your measurements match the numbers on the diagrams, then your print is to scale and you may proceed. Accuracy need not to be tight for the antenna to perform well.

Now superimpose both prints, until they match at around element 10 or 11, and tack them together with scotch tape or white glue.

STEP 4: Cutting the Paper Clips and Fixing Them

You have to trim the paper clips with a nibbler or plier to fit the vertical bars ("elements"). This is fairly straight forward. Lay the paper clip on the template's element and mark the ends with a marker. Snip at the marking.

Make sure that each element fits correctly the length of the bar on the diagram.

Fix the elements in place with crazy glue.

Leave element #2 for later. This is the element that connects to the electronics and is called "the driven element" (as in being driven by electronics).

STEP 5: Building the Backbone

The backbone holds the shape of the antenna. I just cut pieces of popsicle sticks and fit them between the gaps of the elements. I used white glue to fix them in place.

Start from element #15 backward. When you arrive to element #2 move on to the next step.

STEP 6: Building the Driven Element

The "driven element" in a Yagi antenna, is usually the second one from the start. It is the element that connects to the USB WIFI or 2.4 GHZ electronics.

It is a broken loop and not a straight wire. A loop of wire resonates at a specific radio frequency depending on its dimensions. The dimensions of the driven element in this antenna is set at 2.4GHz, of course.

It just happens that its about the size of a common big paper clip. You need to clip the paperclip so that it loops around and meet in the center but the end not touching, leaving a gap (see photo).

Fix it in place with crazy glue and build the back bone around it.

When all the elements and sticks are in place, reinforce the antenna with another layer of popsicle sticks. Glue full lengthed popsicle sticks on top of the antenna. The antenna should become mechanically stiff. Then rip the paper template of the antenna.

STEP 7: Connect the Antenna to the Wifi Modem

This is the most difficult part and depends on the electronic hardware you have. please read this step carefully. 

The basic idea is that you need to solder a wire between the WiFi board's RF output and the driven element of the yagi antenna.

But USB WiFi modems come either with an internal antenna or with an external antenna. Those with external antennae, like mine, are easier to connect because you are just replacing the external whip antenna with the Yagi. Those with internal antenna may need to have their on-board strip antenna modified as illustrated in the pictures here. You need to slightly experiment in this case.

I have tried soldering a coax to my board's antenna connectors and the two ends of the yagi's active element loop but it did not work in my case. I have no explanations why that did not work, but other DIYers that have built Yagi antennae connected their antenna in this manner.

In my case, I just connected a single thin strand of copper wire between the active element of the strip antenna and one end of the loop of the driven element.

Please read the annotations of the pictures for more details.

STEP 8: Performance

The performance was pretty spectacular for this easy to build antenna. I was able to see the WiFi of a hotel that was 2 miles away from my home. The most difficult part was connecting the antenna to the USB modem.

Comments

[Saarducci]

Okay well I read through the entire post and I saw many things that made a lot of sense, also saw a lot of unnecessary flaming, but I do have a few comments to make. Right off the bat the one individual that asked about having his modem in the basement with a rotating antenna on the roof needs a reality check. Overlooked in the connecting the USB dongle to the antenna was the transmission line length, for these frequencies it should be as short as possible and a multiple of 1/2 wavelength I'd suggest as close to 2.41 inches as one could manage (use a small diameter 50 ohm coax). Take the dongle apart and connect a USB extension cable to it and mount it directly on the antenna assembly. Paper clips vs copper, at this frequency it's not going to make much difference, however the specific model was generated using 14awg copper. Someone said glue it all to cardboard then cover it with more cardboard actually a strong and stable design, original author said build around popsicle sticks(wooden), both are subject to absorbing moisture from the air and either can have a poor dielectric constant, I would suggest some kind of plastic (they make popsicles with plastic sticks). The lengths of the elements, the spacing between them, and keeping them all in the same plane and parallel to each other is the most important consideration. The driven element, #2 in this design: that one I would make from 14awg copper, I'd make a simple dipole rather than a folded dipole, I would take two pieces of wire make 90 degree bends in them cut the bent part to about 1/8 inch and attach my transmission line. Take a piece of heat shrink cut two notches in it about 1/4 inch apart and insert the wires into it and shrink it, maybe reinforce the space in the center (break a tooth from my comb and stick it in the middle before heating the shrink?) cut it down to the correct overall length and insert it last. If you use the folded dipole make sure the folded part is perpendicular to the plane of the rest of the antenna and use 300 ohm twin lead to connect to the dongle, but your SWR will probably be much higher, reducing your effective gain and possibly resulting in early failure of the dongle. Horizontal vs vertical, after you have your antenna connected and have connected to some network you can try rotating it about its horizontal axis to see if you can get a better aspect on the other antenna (more bars). All in all though good job to Biotele, it's cheap, it's easy, and if done right will provide excellent results. I did not build this antenna, but I built 2 antennae very similar before reading this post, My son and I live almost 2 miles apart and either of us can stream 1080p movies from the other's house during a thunderstorm.

[sharpstick]

Was the setup with your son line of sight, or was there any foliage between you? Was this able to extend the original wifi network to the second location? (ie. can origin house have broadband wifi and secondary house have its own wifi network piggybacked on the first?)

[Phoghat]

thanks

[Squidyman]

I think you could make an instructable out of all that :D

[m_shulton_arizqi]

Can i use just 4 directors ?

[ПецкоФ]

I still dont get where to put the wires on the natena.... I have USB wifi with external port for antena, I have the coaxial cable... Bit did not see ani diagram where to solder them on the antena.. May be I miss something because of poor english, so please someone to help with a simple diagram on Paint.

PS This looks exactly like an oldschool external TV antena. If I use one wouldnt be better ?!

[zombieregime]

If your wifi adapter already has an (SMA?) output jack, you can either sacrifice an old omni and snip it to get a SMA to bare coax 'pig tail'. Solder the core to one side of the driven loop element gap, and the shield onto the other. Then just plug the SMA into the dongle or extension cable to wifi device.

Sure, you could use an old VHF TV yagi antenna....But youll get awful reception at wifi frequencies. The terrestrial TV yagis are tuned for a frequency in the tens to hundreds megahertz, 137.5MHz for instance has a wave length of about 7 feet(2.18m). 2.4GHz is, like, 11.99cm(4.72in) For a good dipole (which a yagi exploits the way the undriven elements warp and focus the RF waves in way thats not really analogous to a dipole, but still) You need both legs to be 1/4 of the wavelength you want, so 1/2 wavelength over all with the coax tap in the middle. 1/4 attached to the shield, 1/4 to the core, this ensures that as the tip of one leg is (lets say) building negative charge the other leg is building positive charge(....its RF voodoo, this is a conceptual example, not proper physics....). If side A is at its max - and side B is max + there is a potential across the legs that drives a (tiny) current through the radio that is electrically between the two. Pass that current through an amp, and a demodulater, youve got a signal! But if your antenna legs are in the wrong spot or wrong length (physically or electrically) the waves could interfere with each other and cancel out some of that induced current.

Thats the long way of saying you gotta match the antenna to the frequency otherwise, in some cases, its worse than just a length of wiire hanging out of your radio. And/or, Nah, a tv antenna wont do it.

[ПецкоФ]

Got it. Thanks for your answer :)

[Jackv3]

How do i know if the printout is the right size???

[zombieregime]

Measure it.

There are ruler apps for phones that can calibrate fairly accurately to everyday objects like ID cards or coins.

[pranshul12345]

I am using TP link wn722n
And want to make yagi antenna
I had made antenna but I did not getting an idea to connect it to my TP link wn722n
Please Help

[Roland Kakuru]

Thanks upon this project. For my recommendation, I would advise you to use a usb to Ethernet adapter then feed your router with Ethernet as usual.

[timismobile1618]

I'm a ham radio operator and have build many yagi antennas and am going to build this one. Here's a suggestion. For the boom go to Home Depot or Lowe's and get a cheap ($2) wood yardstick that has millimeters. Then you do not need to print out the guide. Also realize there are factors outside your control so getting accuracy to about 1 mm is good enough for element spacing and length. If you aren't that accurate, it will just decrease the gain some, but the antenna will still work much better than an omnidirectional one.

[Mosh44]

can aluminium be used instead copper?

[zwzserver]

As others have pointed out, the impedance matching is done poorly and not even explained properly. I have added a picture of a matched element that also acts as an impedance transformer. The 2.4G wavelength is roughly 5in and the total wire length used in the design should be half of that, but also multiplied by the slowdown factor which is roughly 0.7. That means you use a 2in wire, solder the center of the coax to its center, then fold one leg in half and solder it to the shielding. See image. This is why those internal laptop antennas out of stamped metal have that shape. It's the quarter-wave hoof.

[Rahulsinh jadeja]

Can anyone tell me how to connect this to laptop

[zwzserver]

Assuming your laptop is less than 20 years old, it will have USB ports which means you can follow the instructions as stated. Since you're asking that, I'll skip the option of connecting an R-SMA pigtail internally.

[EliterA]

How the heck do you make precise cuts? I have a dial caliper that measures up to 6 inches, and gets down to the thousandth (0.001) of an inch. I can convert your mm to inches, but I still can't seem to find a non-tedious way to cut a 14 guage piece of steel wire to precise measurements. I want to know how non-precise you can be with these, because not even a million dollar company with the greatest factory can give accuracy to a theoretical set amount of millimeter cut.

[GeoffV2]

I understand that skin effect is paramount to impedences and that if you increase the diameter of the driven element you can also increase the bandwidth and decrease the impedance to like 50 ohms and that a good measuring stick is your best friend in building these things as long as the math formula is good. but to keep resonant a yagi-uda myst always be tuned for each frequency wanted. A tube within a tube allows you to adjust such lengths. Skin effect means tubes are better than wires which are heavier. BUT, where are the formulas for the driven lengths vs diameters and velocity factors of whatever cables ?

[ArakR]

Can someone please make a video with the instrucions in the comments, because its very difficult to follow.

Can I use a USB Wifi wireless WCDMA router for this? Can you give me a model of something acceptable?

I need to catch the signal on 50 meters sometimes, sometimes longer.