Instructables

The Wireless Internet Cantenna gets Dished

Picture of The Wireless Internet Cantenna gets Dished
I just built this Cantenna, and I must have an addiction to the internet or something because I'm hot-rodding the poor thing.

In this, I describe how I use the Cantenna and add it to an old satellite dish.

First, you must have a Cantenna. If necessary, search for that on this site or in google.

Then, you need an old satellite dish. It might not be like the one I use here, so take a look at: http://people.wallawalla.edu/~Rob.Frohne/Airport/Primestar/Primestar.html This primestar has an easy to use feed arm. I had to improvise a method of mounting the can, because the arm on my dish doesn't go all the way to the feed-point area.

Tools were just a couple wrenches to re-configure the dish, a phillips screwdriver to rip apart the old lnb's, a utility knife and a roll of electrical tape. Oh, and an ink pen.
 
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Step 1: What the cat drug in

Picture of What the cat drug in
So I decide to build this, I drop by a friends place and grab his old dish and drive up to the shooting range. Now to see just what exactly I'm going to be dealing with.

There's a pair of LNB's on a y-adapter. The y-adapter is a two-piece clamshell plastic affair that looks rather doubtful. It looks like I'm going to have to add something to get from the arm to where the cantenna is going to go. Oh well, I'm feeling determined at this point. Besides, if I tear it apart enough, maybe something will inspire me. It's happened before
Looking at your side on photo, if that is how you actually direct the dish the 'beam' it is receiving is about 20 degrees below the horizon. As its an offset dish (oval) its designed to collect the signal without being interfered with by the feed. Best way to check is to look at the dish from its tagrget and have someone tip it back to the sweet spot, thats when the oval shape appears to form a circle - you are then directly in its beam!! Hope that makes sense, and if you already knew all that sorry again.
You have the right idea. Assuming the chimney top is flat level, 20° is about close enough. The body of water you can see in the background is where I was aiming, at one of the buildings on my side of the water. I've heard elsewhere that an offset dish is really just an oval section taken from a standard parabolic shape, the center of the offset dish being also the center of a comparable center-feed. It's a compromise that ignores some small signal losses in order to make the dish as small as possible. I've also made another compromise by placing the can so that it catches background radiation. It would be better to have the can aimed upwards so that it's 'peripheral vision' as it were would only have the open sky past the edges of the dish. As you can see, I took the easy assembly route...
Heres a question. What would happen if you put the feed smack bang central?? I know you would get losses from blocking but would the 'beam' be straight or would the beam converge to a point?? Is there a simulator that could show this?
The dish I used checks out with the method of construction that the factory guys use. It really is just a standard parabolic reflector that has been cut into an ellipse. If a feed should be mounted dead center on this offset dish, the result will be about the same as taking a center-fed dish and cutting most of it's reflector off. Providing that you get the feed at the right distance for the focal point, the beam coverage will be at a long distance, but most of the signal is going to be lost. You can usually count on a noticeable portion of the outer edge of the reflector as not useable on any type of dish. That's normally not a problem as the dish will be built to compensate for this. The important thing is that the area that is used for reflecting most of the signal is very marginal with a little dish like mine. Blocking any of that central area will have a big effect.
Would this work for boosting a signal to receive wireless from a cell provider like Sprint or AT&T. Currently I have HughesNET and it is terrible.
Not as simple to do that. This was based on using 802.11 frequencies with some form of external antenna. Though you could do some research on what frequency the cell phone uses, chop off the antenna on your phone and convert it to a removable antenna, with the old antenna soldered onto a connector so you can still use the phone as normal. Then another connector to some coax, to another antenna mounted inside a waveguide sized for the cell frequency. That, you can aim at a dish, and it should get some amount of gain over the omni-directional your phone came with. You could reach a cell tower better while outside of the normal coverage. Something I've been thinking to do for my house. I would try to trouble-shoot your sat connection first. If operating properly, I would be happy with that much data rate!
Thanks for the info! Is there any way that you know of that I might be able to increase my sat connection from my end? It's not a real big deal being that we are capped to 450MB transfer per 24hrs, but it still would be nice to be able to increase my speed.
per 24 hours? -impolite comment-! I never had to think about my connection like that before! pm me, I can either clear the air or pretend to...
If that cell freq is too far out of range, the waveguide might be so big, you'd need to think about parking your car inside it....
lol i just bought a 10ft usb extension cable.
drboose5 years ago
This looks alot like the wiffy extreme antenna.

http://w3bguru.com/wiffy-extreme/
Shadetree Engineer (author)  drboose5 years ago
Absolutely correct! What I built can be described as an offset dish fed with waveguide, the same as how the wiffy is described. Only they used a different set of dimensions for their waveguide, possibly getting a better result than what I did. However, the focal point of both mine and their dishes requires both of our waveguides to be placed very much in the same position. So it really should look like mine if it's going to work right....
I made time ago similar stuff using a 60cm dish & dia 8,5cm/13,5cm long coffee can (best feed for F/D=2/3 offset sat dish) with an Usb Key mounted thru the bottom of the can (its ceramic chip antenna positioned in the middle 3cm from the bottom of the can!) ... so a feed was 10dBi mini active Cantenna & it looked this way .. side view .. side front view and side back view ... taking of account the obstacle (old feed!) , this 15deg offset active antenna had a maximized gain of 24dBi !
Ruan20085 years ago
yuckzee5 years ago
i have proubly a old satalite dish that is proubly around 10-15 feet wide, but it is like metal mesh but how could i use that to make a wifi thingy?
Shadetree Engineer (author)  yuckzee5 years ago
Ah, drool....drool! The metal mesh is just fine, as long as the holes are near 1/16th inch. The wi-fi waves will not pass through holes that small and will reflect back off of the mesh instead. If the mesh uses a large size hole, you should still use the dish because of it's parabolic shape. You would then need to do something like attach aluminum foil. If you seriously want to use this thing, maybe you should PM me under my profile.
chrisbolt5 years ago
Its my first time in instructables,flaring the opening of waveguide by about 20 to 60 deg angle and a length of 2 to 15 wavelengths from the apex of the flare, reduces reflected power and impedance mismatch. Flare antenna known as horn antenna is use in communication link.
I've been reading a LOT of this WiFi stuff here on our extraordinary Instructables.com and was wondering if anyone has tested the strainer method against the coffee can or pringles method and also against using an old directv satellite and such. Which one would give me the best reception? I'm guessing the satellite dish but I am new to this. TIA!
How do you weather proof the receiving portion?
you probably can use clear plastic covering
pyper5 years ago
Does anyone know the sort of gain you could expect from one of the little oval sky TV dishes, I've got a nice big 90cm dish up the garden but i want something i can just hang / mount out my window.
Derin6 years ago
you wouldnt,only Turksat allows free satellite TV
tyeo0986 years ago
Cover the dish in tin foil, that will give you better accuracy and allow more rays to be reflected, and not absorbed into the dish. It should work because its meant to pick up Sat signals ~300MHz and wifi is about ~2.4GHz, nice job though! I might build one to make a LoS (Line of Sight) transmitter finder, to find lost model rockets(big expensive ones). No more lost rockets for us!
Shadetree Engineer (author)  tyeo0986 years ago
I wouldn't have expected aluminum to reflect better than steel at any particular frequency. Do you have any websites with more info on this? I'm very curious. I can test it quickly enough though. But I still have some side lobes to elliminate. Basically, turning the entire dish 10 degrees in either direction from the position that gave the best signal, would drop the signal completely. Then turning the dish further away would bring the same signal back, but very weak. This would happen around 80 degrees in either direction. I'm much better at building the physical structure of this stuff, I still have a lot to learn concerning the unseen aspects.
Okay, some research of my own initiative is turning up some very interesting info: "Many of the small aperture Ku band dishes sold these days use an offset antenna feedhorn design which places the focal point below the front and center of the dish. This type of antenna, which is actually a small oval subsection from a much larger parabolic antenna design, is oval in shape with a minor axis (left to right) that is narrower than its major axis (top to bottom). Because of its unique geometry, the offset fed antenna requires a specially designed feedhorn which matches the antenna geometry precisely. For this reason, the offset fed antenna and feedhorn are usually sold together as a single unit." So I need to know what makes my cantenna not 'special'
post up a pic of it and we shall see? probably just need a bigger collector?
Shadetree Engineer (author)  last_decoy6 years ago
This is from my one of my first instructables. It was a fire extinguisher with the top cut off. I never got around to tuning the length, I just keep using the can as is for newer antenna designs. I'm thinking about some kind of folded wave-guide. Basically put the small can inside of a larger container, aimed inwards. But I want to use a 5-gallon bucket, and if necessary, just change the small can's dimensions to fit. My latest design put's a cone on the end of the can. Aperture about 9 inches, length determined using a waveguide program. I'm curious about putting wire loops in front of the cone, to make a virtual cone. I tried once, but I made the loops all the same diameter as the cone aperture. Next time I should try something like a 5 foot diameter loop 20 feet in front. Or I could build a 'Metal Lens' antenna, which is proven to work with any narrow focus directional antenna.
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Your essentially correct. Scott you are also essentially correct. Anything for DBS has to now be swept tested up to 2.4 ghz. That particular dish you are using has anywhere from -28 to -32 db of gain on satellite frequencies, depending on the dish. Something as simple as an imperfection in the powder coat can throw off the curve of the dish and throw off the gain. Without doing a lot of math and everything what you could do is hold the LNB approximately 2 1/2 inches from the end of the support arm and center with the support arm and use a straight edge or even a piece of string on the LNB to determine where the prime focus of the dish is and then prime focus your Cantenna or director or whatever you want to call it in that same area. Also without checking FCC code this antenna is fine to receive with however transmitting with such a set up may or may not break Federal, State, or local codes.
look depending on the wave or frequency. a signal will be reflected happily by even mesh. notice your microwave oven has a fine mesh inbetween the glass or plastic door window? yea the wave height is far to big for it to fit through the little holes so it doesn't, and u are safe from the radiation. same thing applies to all electromagnetic wavelengths. covering it with foil will make your well thought out plan look very silly.

and Shadetree where are you pointing your dish? and what frequency. if you had an analizer you could distinguish between what you want and noise.
remember if ur pulling signals from a long way away eg: a sat. one degree may seem like nothing but once u get out there its a very big distance.
Shadetree Engineer (author)  last_decoy6 years ago
Dish was built with a 2.94 Ghz band wi-fi adapter. Aiming 10 to 30 degrees below the horizon at a motel, about 1/4 ~ 1/2 mile distance. I wish I had some kind of analyzer.
w8tvi tyeo0986 years ago
Um, Dish Network's satellite downlink is around 12 Ghz (the Ku band), not 300 Mhz. the metal in the dish will work quite nicely for 2.4 Ghz
DSS uses 12ghz. tin foil?? sheesh.
Shadetree Engineer (author)  Scott_Tx6 years ago
I just read somewhere that frequencies such as 12Ghz should use silver-plated pure copper to get the highest level of performance. At 2 Ghz, the losses are so low that you can get away with using aluminum or steel.
last_decoy6 years ago
the dish will reflect fine adding foil to it would make it look silly. my dish. real internet dish is made of clear acrlic with a fine 0.014 stailless mesh in it. good idea, lol
Shadetree Engineer (author)  last_decoy6 years ago
That would be one nice looking dish! I want to see one! What about using a cheap sat dish as a molding blank to vacuum-form a warmed-up sheet of acrylic, then machine the back side with some kind of jig, and then spray the back with a metallic paint? Kinda like how a mirror is made, the coating can have high spots, but the surface it's stuck to will show through as a perfect mirror. It's the jig I'm really wondering about...
would be fine, just in the long term sun damage and heat warping (more sun) would suck. and the metalic paint will have to contain metal.. but now im just poking at tiny problems. you will be amazed how a wave finder or a CROW makes testing and operating really.. well... good!
Shadetree Engineer (author)  last_decoy6 years ago
We need someone to post an instructable on building a metallizing gun, though I haven't looked yet... What's a CROW?
dkrmwiz6 years ago
will this work to pull in the wireless internet signal that at&t or verizon puts out? in our area we'll never get conventional dsl, (phone company is too cheap to lay cable) or cable modem (same reason). we have directv for satellite, but i've heard bad things about this type of internet. i know the wi-fi is better, but want it to really work. we're on dial-up at the moment at a lovely 26.4 k hook-up speed on a good day. we've got to get something else! any help would be great!
lwltcl6 years ago
This looks good, but what is a cantenna? Is it a can if so what size can? Is it like the Maxwell coffee can or a fruit can?
Shadetree Engineer (author)  lwltcl6 years ago
I'm starting to re-think the classification of my original cantenna. For most people, the tube I have aimed at the dish is a cantenna. But that is when the name is used loosely, as it is really acting more like a wave-guide. A proper cantenna will have an additional bit of hardware inserted inside which acts as a director. This will usually look like a rod with a bunch of washers spaced an inch or so apart, just like a 1950's raygun. I would recommend looking on this site for a yagi-cantenna, as that is built in the manner I have just described. A large coffee can with a funnel on the open end will work as a wave-guide. If you don't mind doing a bit of homework, check this out:waveguide