The Conetenna - a wi-fi antenna

Using parts from previous wi-fi antennas I have built, I attempt to create a monster antenna, yet only to wind up with an ordinary cantenna wave-guide with funnel attachement.

Step 1: Harebrained idea

I saw some info on how to make a Patch Style antenna for 802.11 networks.

I thought if one director was good, maybe more would be better. So I used the dimensions from the patch antenna to determine an aperture for a conical wave-guide, this so that I could use my fire-extinguisher based cantenna as a wave-guide feed. The patch directions recommend going to a store like a dollar store for a lid. I happened to find some cutting boards that were just big enough and bought one to test in the microwave. Passing that test, I purchased more and decided to use 3/4" pvc tubing as a frame.

W1GHZ
This is the page where you can find the latest version of the waveguide calculator, which I used to find the right length for this cone, based on the diameter of my existing cantenna waveguide, and on the 242mm diameter directors. This software indicated a possible gain of 13 Db. If it came close to that is still unknown as I still need to learn how to measure that. This is also where I can learn how to measure my results, if I would just spend more time there!

Seeing as I'm throwing in software links - Delta Cad is what I use to draw my designs. However, I took several years of drafting classes and what little of that I can still remember is not included in the help section that comes with Delta Cad, sorry.

Comments

[_Scratch_]

I had an idea for a wi-fi range extender, but im not sure if it would work... I would have a 2 liter bottle wrapped in aluminum tape magnetically suspended in a trough that is a bit wider than the bottle. I would have a compressed air tube put in the bottom of the trough, facing up, so that when you blow air through it, it spins the bottle at a few thousand rpm. when it's spinning, I would put a wi-fi transmitter next to it. I have been told this would act as an antenna, with the bottle throwing the signal farther or something. Can anyone confirm that this would work?

[jimvandamme]

All this would do is splatter the radiation all over the place, and thus make it weaker. It doesn't amplify it or concentrate it in the direction you want, plus it would put lots of nasty modulation (PM and AM) on the signal which would probably make your receiver inoperative. I'd like to know where you got the idea.

[Shadetree Engineer]

Wow! I'm curious who would tell you this, and what their reasoning might be.

By magnetic suspension, I'm assuming you will attach magnets to the bottle, or something.

But if you want to spin the bottle using a stream of directed air, why not just use the air itself as the suspension?

And just putting the WiFi transmitting unit next to the bottle may not be enough. If there's any effect at all, I would expect it to be affected by the precise distance between bottle and WiFi antenna, orientation of WiFi antenna, method of applying the aluminum tape - pattern of seams, capacitance effects from layers of aluminum & tape adhesive, if magnets are involved what about any possibility of eddy currents being generated inside of the aluminum - which goes back to the pattern of the tapes orientation, I would be tempted to try coating the inside of the bottle with a thin coating of paint and then aluminum powder such as Stop Leak for radiators, and if the bottle did anything, there will still be the amount of energy being transmitted by the WiFi antenna in directions away from the bottle so if you are thinking of generating a kind of magnetic containment field extending beyond the bottle then good luck! You will need some very serious measuring equipment to tell what's not working right. I think you should consider how to control the bottles rpm's very precisely. And try to figure out a method of detecting eddy currents. You might be doing nothing more than creating a very bad power generator at gigahertz frequencies. But it sounds like fascinating research. I would recommend using a very directional WiFi antenna. Maybe that trough should be the open end to a circular waveguide? Or a open-faced resonance chamber that faces towards the bottle's side, and the WiFi radiating element inside that?

[_Scratch_]

Alright, by the magnetic suspension, i would place the magnets in the bottle so the currents are irrelevant, and I would think it would be hard to get an even suspension with compressed air whereas with magnets, I can just glue a few rows inside and on the back of the trough, and I get an even levitation.

[_Scratch_]

Another alternative method to "spin the bottle" would possibly be to hook it up to a medium sized Tesla turbine, so I could still achieve about 20,000-30,000 RPM, while still being able to accurately adjust the speed with small air pressure adjustments and a simple meter to gauge the RPM.

Also, to the resonance chamber, a satellite dish would probable work well, with the Wi-fi source at some point behind the focal point, and the spinning bottle in the middle of the focal point, so it would spread out the signal that hits it, assuming it would actually work in that way.

[Shadetree Engineer]

Oh, so it would be okay to mount the bottle to a shaft? I thought you were going through all that magnetic suspension to create an airgap. Well what about using a variable-speed dremel to spin the bottle? Dremels have all kinds of attachment methods to put anything on them. Might be cheaper than buying an industrial disk turbine, unless you were thinking of building one of those. But even an air-powered die-grinder could work and you can buy one for less than $20 However, I would be cautious about trying to spin a bottle at such high speeds. Getting it to stay perfectly centered and balanced wont be a casual thing either.

http://www.w1ghz.org/antbook/contents.htm - this is a good place to start refreshing your design approach.

[_Scratch_]

I would think the magnetic suspension would still be relevant considering that the bottle would likely be rather unbalanced just hanging from a shaft.
there are a few 'ibles on here that show how to make a Tesla disk turbine from some old hard drive platters, so it wouldn't be too out of reach, and I was thinking that the turbine would be better than a air powered die grinder since it would use a decent bit less air, since I wouldn't want to invest in a huge air compressor, that way, the air tank could be continually filled. I suppose a Dremel would work, but a corded one would be necessary for the higher power and endless power supply.
I would also assume the magnetic levitation would keep it balanced and rather centered, but I could be wrong

[Shadetree Engineer]

I own an air-compressor and I have used it a lot, so I can say for a fact that if you can use a Dremel with good results, then that is preferable. Besides, if you get any useful results with this antenna design, you might want to run it for hours at a time.

A magnetic suspension is a very flexible sort of thing, so any kind of oscillation will build up very quickly into an unbalanced condition. I suspect that designers of high-speed maglev trains will have some interesting points to say about this. Try to imagine a maglev running a continuous loop at 230 miles per hour. Which is approximately the surface speed of the bottle at 20,000 rpm's. This only means that you need a very well thought-out arrangement for your magnets. Placing magnets on, or inside the bottle will probable stretch the diameter of the plastic at very high speeds due to the mass of the magnets acting under centrifugal force.

This kind of speed is one of the reasons why Tesla never got anywhere with his turbine design. Using the materials available back then, the disks kept shattering at any useful speed unless they were a very small diameter. But then the total horsepower was too low to be of any value for what he wanted to do. A scrapped hard drive disk is engineered to spin at a high speed. But they are rated for a speed that wont flutter at a microscopic level, you can actually run them much faster if all you want is to not shatter.

I would highly recommend that you skip all of the WiFi stuff and focus on simply spinning a bottle. And try to control the speed through as wide a range as possible. Maybe you shouldn't be running above 1000? You don't know yet what to expect from a spinning cylinder placed inside of a 2.4 gigahertz EM field.

[_Scratch_]

I suppose so, for all of it

[Shadetree Engineer]

Well, if anything interesting happens, let me know. I tried to find any info on that kind of idea. But it looks like a total unknown. Doesn't mean that no-ones tried such an experiment. Just that it's one of those things that isn't easy to find.

[tapplicat'on]

I have an ADSL/Router, will this antenna work for that too? And what about the weather conditions?

[Shadetree Engineer]

If you look-up 'cantenna's, you'll find that they use a patch cable to connect a WiFi card to the side of a tube. Just like this antenna. So yes, you should be able to use your router. Even better if you can change it's firmware to DD-WRT or other open-source firmware. The simplest way to put your router and this antenna together, is to skip the patch cable & connector. Take all the plastic off of your routers antenna, so it's just the inner cable. You'll see that the end of the cable is bare, this is the actual antenna portion. For something like my antenna, you would drill a small hole instead of cutting the square hole for the adapter that I used. Then that router antenna can be glued in place, inside that hole, with all of the bare section inside and only a sixteenth inch of the outer shielding going through the hole. Make sure it goes in straight. Then tape or glue the router right to the side of the can. Take a look around for 'power over ethernet' to send power to the router using just the ethernet cable. Then seal the whole thing so it's watertight. You can use a 100 foot cable. Rainy weather will reduce the signal. That frequency is blocked by trees & bushes too. The antenna could be put inside a plastic bucket with a snap-seal lid. So that might be a good way to make it weather-proof. Just run the ethernet cable through a hole in the bucket and silicone that tight.

[ayvz]

ahmm
sorry for that..
its very hard for me to do the conetenna..
we have a group project..and we choose conetenna for our poject..

[Shadetree Engineer]

No worries.

You could go to my profile and send a message directly to me about this group project.

[ayvz]

can we use the pringles instead of cone?

[Shadetree Engineer]

If I understand what you're asking, then no: The Pringles tube does not make a signal match from the USB module to free-air.

What the Pringles tube does is the exact same thing as what the fire-extinguisher tube in this instructable is doing. Only the dimensions are different, and so the performance will be different.

You can use a Pringles tube along with a matching cone to improve the performance over just the Pringles tube alone.

The cone is an add-on. You should just get the tube to work first and try changing how it's made several times before going to the next part of designing a cone.

[ayvz]

is it needed to have a wifi usb?

[Shadetree Engineer]

Is what needed? The entire instructable? The disks? Oh wait, this is a philosophical question, right? So no, a usb wifi is not needed. But it could be valued somehow...

[george50k]

Nice, you can read more about antennas diy
I think the cone amplyfies the signal, the signal is a wave in the air, if you can do an aluminium cone, i think it could be better. Try to put the cone near your ear, i think that the wave (wifi signal) can be the same as the sound waves....

Nice, I will do somthing like that.

http://www.usbwifi.orconhosting.net.nz/
http://www.aircrack-ng.org/doku.php?id=es:cantenna_directional_antenna_with_gain

[Shadetree Engineer]

Go for it!

By the way, this used an aluminum cone. It's a composite style construction. The plastic cone is just a form to hold the aluminum in the right shape.

Yeah, putting a cone to your ear will help you hear more of a sound. But that still is not amplifying the sound, only reducing the amount lost. For the WiFi signal, most of that will not enter the antenna. A cone will help reduce that loss.

[saysay]

sir, me and my friends are making a contenna..we are using a tin can..then connected to a steel cone..we have a problem in determing the antenna gain of it..i hope u can help us..

[Shadetree Engineer]

Well, I never bothered to learn how to measure antenna gain. So I wont be able to help as much as you would like, except that I think you might get a better answer if you post this question in the 'WiFi Antennas' group here on Instructables. Of course, the group may not look like anything is happening as the posts are getting old, but still give it a try as the group members should be e-mailed from anything getting posted there, and they may respond with better ideas than me.

Otherwise, you will have to use the google same as me.

en.wikipedia.org/wiki/Antenna_measurement

I might try a more practical measurement.  Just measure your connection speed by searching google for 'speed test' and using one of those results for a server that's close to where you are.

Do the same test using the bare adapter, and again with the waveguide

Take the result for the bare adapter and write that down on a sheet of paper. Double that number and write that down underneath the first number. Keep doing that until you get a number that is bigger than what you got using the waveguide. Count how many times you had to double the first number without going past the waveguide result, and multiply that by 3 (every 3 dB is a doubling of power). Assume that your adapter is 5 dB by itself and add that to the result (you could of course try to find the actual dB of your adapter).  This will be a number of decibels that you will not be able to use in comparison to anyone elses antennas.  This measurement will be only for your own use, to see how well you have done.  If you build another antenna you can use this approach to see what change there may be in connection performance.

[Waren-Neutron]

are you a engineer ?

[Shadetree Engineer]

Nope, I only pretend to think like one. I searched google for a good description on how decibels work, then re-interpreted that to our discussion. I'm assuming data-rates are scalable in proportion to received signal-level. I'm also assuming that accuracy is not as important as consistent results. Always remember to measure for yourself some existing antenna to use as your reference, preferably a stick style or 'dipole' that receives in all directions if you want to get closer to being able to compare to other peoples designs. But they might not be as careful about such things, how will you know if their numbers are worth anything? - build their design and test for yourself!

[Waren-Neutron]

TRIVIA;
you know that antenna is a 5 of the type of wireless antenna !
It is a DISH is a type of antenna that you use .
Additional it is commonly use in towers or communicating towers
and also for wifi

[BodhidharmaCharma]

Has anyone built this and had good results? I want to make sure this works before I commit to building it (sticking out of my dorm room, folks might think I'm crazy!).

[rayfalcon]

hey this gives me a very fantastic spying pc (laptop ) idea use this and one of the microphones from a tape recorder or an old pc that are builded into the system and place the microphone at the smallest end of the tube and use it to amplify sounds, voices ect ect and record them on the pc with sound recorder ....You could also use it as a security feature at home to detect unwanted visitors approaching i.e burgulars, or perhaps those pesky door to door salesmen. Have fun and Great instructable a 5 star rating for you.

[Shadetree Engineer]

Okay, but I would make a few changes - like don't block the end with that solid disk, use thicker walled tubing like a cardboard center tube from a carpet roll, and make the cone from several layers of poster-board to get a decent thickness. The added thickness will help keep sounds from getting through the sides and leave only the ones you want. Then mount this in front of a plywood parabolic dish and you will have a very interesting acoustic listening device. For a laptop that can spy, maybe you should try getting closer to the action. Just use a laptop with a built-in camera. Those usually have a built-in microphone as well. Then load this: http://preyproject.com/ I'm not suggesting that you borrow someone's laptop to do this.

[saysay]

How to determine the gain of a particular cantenna?

[Shadetree Engineer]

You need a good way to measure signal strength to do that. And just rotate your antenna a full circle in 10 degree steps, or whatever you like, while measuring one signal.  The change in signal strength at each position will tell you what the shape of pattern your antenna has, and how well it focuses in the forward direction.

As for determining the actual gain in decibels, I wouldn't worry too much about that.  I think the shape of the antenna's radiating pattern is more important than what it's numbers are.

[saysay]

what is the polarization of the conetenna?
and the waveguide of it?

[Shadetree Engineer]

I'm not really able to answer that, due to a lack of serious testing.  What I can say, is that I have decided to use a default setup where the adapter is clocked at either the 3 or 9 o-clock position. That is, sticking out of the side of the Conetenna horizontally.  That seems to get the best signal most of the time.

I would highly recommend that you rotate your antenna and check your signal level yourself, as the conditions you will experience may be different from what I have.

I believe that the adapter has a linear radiation pattern from itself, so a circular type  of polarization is not going to happen here.  That means that the circular cross-sectional shape of this waveguide is likely not the best idea, but is just a construction shortcut. A rectangular cross-section with the right ratio between long and short sides would be better.

[saysay]

why u combine the plastic and aluminum?
is plastic good for getting signal?
y u used plastic?instead aluminum alone
what kind of aluminum r u using?

[Shadetree Engineer]

Your suspicion is correct, the plastic is completely useless at getting any of the Wi-Fi signal.

On the other hand, the aluminum works very well at making the signal go where you want. In this case, what I used was some really thin Chinese made foil wrap. They didn't put a steel cutter on the carton, the foil is so easy to rip that just some cardboard teeth will cut it straight across.

One problem with using this foil wrap is that it wont keep it's shape if you even so much as touch the stuff, and the cone shape the foil is patterned after is supposed to be a precision device.

Now what the plastic does, is it makes for a very nice rigid shape that holds the foil in a fair approximation of the cone it needs to be.  As a plus, the plastic is transparent at that frequency and won't get in the way of the signal.  I tested this by putting some of the plastic by itself in my microwave and it did not get hot. (that means it did not absorb any of the energy, or 'block' it - also microwave ovens use almost the exact same frequency as Wi-Fi)

[saysay]

what is the purpose of the cone in your conetenna?
what are the specs of it??

[Shadetree Engineer]

The cone helps get more signal into the waveguide.  It acts as an impedance matching device to free air.  The dimensions are calculated with the help of some radio frequency tuning software, basically the bigger the opening, the longer the cone.  The ratio follows a complicated set of rules so it doesn't really just scale up by doubling the measurements.  Seeing as this waveguide is not really the best choice, I may as well have used a dog cone. i would recommend using one of the coffee can designs instead of a fire extinguisher.  It looks like I didn't put the finished length of the cone into this Instructable, but I did put the diameter of the cones exit - 242 mm. The antenna isn't nearby or I would just measure it and say what the length of the cone is, sorry.

[dongskie01]

sir, is your conetenna connected with a cantenna? or some kind of that thing sir? 

what connector you use from the conetenna to your pc sir? do it need some usb wifi adapter?

[Shadetree Engineer]

Well, it all started with the construction of a simple cantenna, which is actually just a waveguide antenna because I did not include the usual stack of washers inside of the tube like the origional cantenna.  The waveguide worked but I wanted better performance, so I tried aiming it at a small parabolic dish and thereby built a dish antenna with a waveguide feed. That worked better but was not very directional. I tried adding director rings to the feed but nothing worked. And then I read that a waveguide with a cone added to the end could be made very directional and also could get a decent amount of signal if built right. So I spent some time and came up with the ideal dimensions for my existing waveguide. I also tried making it even more directional by adding a crazy amount of directors, but that didn't work so I cut those off and just settled for a simple waveguide with cone attached. And that is what this instructable details the construction of.  I had thought that the more persistent hobbiest might see that I have posted instructables about my previous antennas and read up on those to get a more complete understanding of how this final antenna came about.  This is then, an evolutionary design, and not a very well engineered one at that.  I'm fairly certain that a larger diameter should be used for the waveguide, maybe five inches or more. That would change the required length of the waveguide tube, the distance from the back of the tube to where the hole is cut, and the overall length and outer diameter of the cone depending on how directional it should be.  The entire evolution of these antennas has been based on using the same USB WiFi adapter with a pair of five-foot USB cables.

[0utbreak]

i can imagine the download but what about Upload speed ??

[Shadetree Engineer]

Uploads are a bit slower. The hotter connection from this location would allow me to upload a jpg resized for craigslist default - 300 x 225 pixel - 9~13 kb, in less than two minutes.