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.
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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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
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
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Try this link, It was the DEFCON WiFi Shootout
http://www.unwiredadventures.com/unwire/2005/12/defcon_wifi_sho.html
Could I get signal from over the horizon?
Now mind you I was just thinking, which gets me into trouble a lot of the time with my wife. But could this work?
Seriously though, this isn't a good idea for a bunch of reasons, but I can appreciate the impulse.
The yagi extensions if designed right, will work best when used with a hot element mixed into their stack, near the rear, and not when fed from a wave-guide. So that will just result in a lot of signal getting blocked from the mass of metal in the way of the waveguide opening.
Then, a 4 foot yagi will lose power because after about the 12th element you will only be adding a small bit more. Then at around 25 elements, the signal will be getting absorbed by the metallic mass of any additional element. After 6 inches, all elements will be around 5/8ths inch spacing.
Then, you do not want to use a tightly designed yagi to illuminate a dish as the radiated pattern won't spread wide enough to cover the dish. By the way, you don't want to illuminate the very outer edge of any size dish. That loses some signal due to edge effects.
Then, using multiple radiating sources to illuminate the dish will likely have the signal cancelling itself out from interference patterns. Unless you have access to some very expensive technology to model the energy flow of the signal. Better off to leave the Star Wars stuff to the government.
Now, that being said, a 10 foot dish with a well-matched & designed radiating source will get you to the horizon. Over will require a repeater station, as these frequencies like to travel in straight lines.
I also am not sure if my picture explained it or not but I was thinking that the dish would have a broader area to receive a signal and then reflect the signal at its focal point to the yagi in hopes that it could be a bit less of pin point aiming in the direction of a tower.
Now I was only thinking that if any one of the components were able to boost the signal strength then maybe it would do a lot better if I used all of them into one unit.
On another note would it work if I used the cantenna at the back of the dish with a shorter yagi extending outward?
I am good at building stuff like computers and designing boats and I put together some really weird things that do seem to work.
But I don't understand the math that is involved with wave forms, in fact I am pretty poor when it comes to math.
So please bare with me if I seem a bit mentally challenged But I do work at trying to figure this all out.
Thank you very much for your feed back.
What I mean by a 'hot element' is the little bit of wire that is connected directly to the end of the antenna wire. This usually is simply a stripped length of the coax, with the bare end being the correct wavelength.
You have the right idea for a larger dish being able to capture more signal, but that yagi idea will likely lose a lot of that gain. So you might wind-up with a noticeable improvement overall, but not by as much as you could have had. But only if the yagi can radiate the majority of it's signal in a cone pattern that covers 90% of the dish. A very long, multi-element yagi will focus all of it's signal right at the center of the dish - right where the cantenna is shadowing the dish the most. You can aim the cantenna off to one side, like the Dish Networks antennas are designed, so that the dish is reflecting the signal away from the cantenna. But you will still have the problem of only using a small area of the dish, if you use a multi-element yagi.
Any dish you find is a reflector, so putting the cantenna at the back will require a second reflector at the front, where the cantenna would have been. In this scenario, a multi-element yagi might work ok, as the second reflector should be designed to accept a narrow beam, then reflect that onto the wider main dish. But putting a multi-element yagi in front of a waveguide such as the cantenna is another problem. You would be better off just building a wifi yagi, and forget about the waveguide can. There are many good examples of military radars that use a two-reflector set-up. But the second reflector is not normally seen as a signal boosting device, as it will introduce another set of losses. Putting any kind of metallic plane, to the rear of a yagi, will enhance it's ground-plane effect. Which will improve the quality of the signal, but not because the dish is focusing more signal.
If you do not want to learn the engineering, then you really ought to stick with proven designs. That would just be the most practical choice to get any kind of antenna up & running, to the best of your abilities.
Take a look at http://www.engadget.com/2007/06/19/venezuelans-set-new-wifi-distance-record-237-miles/
All of the world records for Wi-Fi connections over the greatest range all used the biggest dishes available. The small percentage of signal lost from a center-feed shadowing the signal is more than made-up for by the extra diameter.
I'm very strongly in favor of using an ethernet based Wi-Fi for the adapter. You should take a look at this: http://www.dd-wrt.com/site/index - and consider that their firmware has the option to change a router into an adapter that can be plugged into another router. The main advantage here is that an ethernet cable can go well over 100 feet. And if you add-in a 'power-over ethernet', you have a one-cable solution to go from any room in your house to the original location of the sat dish, or to any suitable high-ground such as your roof. No awkward hanging a lap-top out a window kind of thing. It doesn't take much to adapt an antenna on a router to a directional feed. You might not want to use both antennas though. I think the alternate firmware supports turning one antenna off.
Let me know what you come up with.
http://urbanwireless.info has a few good tutorials on making these type's of antennas
The money approach would be to spend $400 on a cell-phone amplifier kit, available from http://www.wilsonelectronics.com
I've been thinking about combining one of those with an unlimited cell phone plan like with http://www.zer01mobile.com/