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Wifi antenna opinions? Bi-Quad vs cantenna as dish feed or alone?

Discussion in 'Radio and Communications' started by ()blivion, May 12, 2012.

  1. ()blivion

    ()blivion Active Member

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    Yeah. My plan was to put a USB dongle *RIGHT* up on the feed. Then there is less places that have to be tuned and such. But then again. my week point in electronics *IS* radio, so I don't really know what's best.

    There are a lot of great ways to get the right curvature I'm told. Spinning a vat of fluid that will eventually harden is one. And drooping heavy hose from two points and cutting out the curve onto your struts is another. There are more and it's more detailed than that, but you get the idea. As for smoothness, IDK... trial and error I guess. But I do see where your coming from for sure. It was just a thought. I would RATHER get a real dish. But I can't find any free ones or spend money. And I don't think they make the big ones anymore.

    Assuming I could do that and did, what are the link speeds? I'm aiming for something fast, but not necessarily low latency. Though both would be best. Also... it would need to be "an internet connection" for my interests. If I need to talk to some one... I have a phone :/

    Thanks for useful comments.
     
  2. Sceadwian

    Sceadwian Banned

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    I know there are methods, go ahead and try doing something like that on a scale for 12 feet or greater :) The spinning pool method is actually used to form large mirrors used in telescopes, not very practical for something that large on a hobby level though.

    Try Craigs list, post an add requesting people contact you if they have any full sized dishes they want removed for free, and check read the free section once every few days to see if someone posts anything. I've gotten some serious finds cruising craigslist for parts.

    If it weren't for the fact that I've already used the bulk of my storage space I would have picked up 3 (yes three) 40-60 inch rear projection TV's this week (all in working conditions)
    But my wife would kill me =-> I still have to gut the last one I picked up.

    You can also go cruising your neighboorhood if you have the time. If you see one the chances of someone still using it are pretty slim, and most people consider them eyesores.

    How fast is fast? I've not looked into it too much, no practical need for it in my area I get 20meg down from my cable connection.
     
  3. ()blivion

    ()blivion Active Member

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    Point taken. You would think smaller would be harder to do right ones self as the tolerances would follow the change in scale, but the wavelength doesn't. But as I said, I know nothing about radio.

    Done it, and then some... nothing in my area if you can believe it. PLACING an add is a good idea though. Also gota figure I have to haul this thing from a to b..... so it should be as close to b as possible, which has been a problem.

    LOL, thats funny as I happen to have one also. I need to give up on it and part out, they are just so damn big and have to picky optics for getting good picture. I payed money for mine though :(

    Good point. I have calculated my needs and average use and I estimate that I can't really live without at least 3meg internet. Though I also need a bit of upload, plus error correction of course. So say 4meg TOTAL bandwidth to be safe.



    On topic, here is a picture of my cantenna with (crappy tinfoil) parabolic feed horn. I'm using it now stand alone, but I have it set up to be converted to a dish feed at any time...
    View attachment 65133

    I don't like how uneven and what not the bottoms of most tin cans are for use as a cantenna. So I usually cut out the bottoms and soldered on a flat sheet of tin in it's place. Not sure if it helps, and it wastes a lot of solder. Here is a picture of that.
    View attachment 65134

    I also like to solder cans together from time to time. Also a waste of solder. But whatevz.
    View attachment 65135
     
    Last edited: Jun 24, 2012
  4. dave

    Dave New Member

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  5. Sceadwian

    Sceadwian Banned

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    What are the dimensions on those cans? I found a ways back a document that shows all the possible dimensions of a Cantenna that fit within the allowed propagation modes (there are two), the length of the cantenna has to be calculated from the diameter of it or you could be losing 3+ DB's with a mismatch there. I don't think aluminum foil is a big issue, the skin depth at microwave frequency is incredibly shallow.
     
  6. ()blivion

    ()blivion Active Member

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    Can lengths are 83mm from the inner surface of both sides of the can. I was careful to make sure that was the longest length I measured, and measured twice from different spots in case the can was oval or something. The length is 34~35cm long (three cans stacked) plus the horn, which is 20cm. The horn is only parabolic/logarithmic for the first 5cm off the end of the cans. Then it's just a slight increase in diameter till the end, but is probably effectively parallel.

    The guide I used (I'll try and dig it up later) came with a command line program that gave you all the necessary measurements from the input of the can's diameter. The guide said that the cans should be at least 1.5 wavelengths long. But it also said that there is no upper limit to the length. With longer being more directionality and gain in said direction and shorter being the reverse of this. The aluminum horn was added as it was also said in the guide that there is a bad interface between the air and wave guide usually. And that this causes a impedance mismatch that a horn will improve on considerably. I would like a better horn that is more mathematically correct and sturdy. But bending a curve into a sheet metal cylinder is difficult to say the least. I suppose I could use just a strait ordinary cone or "funnel shape"... but... meh, it works well as is. I want it matched for a dish eventually.
     
  7. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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  8. ()blivion

    ()blivion Active Member

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    Hi KISS, and great link. Love the first one. I'm not really interested in buying anything prebuilt, so the second one is kinda a non option for me.

    That first link though, good stuff. That's about the goal I would like to achieve. Sadly, I don't have a ham license and the subject is ever so slightly off topic. Though I *COULD* get my ham license I'm sure. And if I can do stuff like that with one... I just might. Looks useful.

    :Checks requirements: . . .

    Oh, So it's not that hard to get at all. Just a small fee and I have to take a test. I could do that easy.

    How hard would something like whats in the first link be to build though? It's microwave, so I would imagine it to be touchy as hell. That link is also old, are most of the parts and services still available? Could I reuse sat TV parts and equipment maybe? Keep in mind I don't really have any fancy radio tools either.
     
  9. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    I thought so too when I ran across it. Finding it again was fun. brain is like, I remember it on the Internet somewhere, now what terms should I use to retrieve it. Is it in Bookmarks? Whose bookmarks? What terms do I use to look?

    Take up a real challenge and not something "easy" like pumps?
     
  10. ()blivion

    ()blivion Active Member

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    LOL. Yeah something like that. Unless "those pumps" break into the MCU world I am going to be of little use to "the project" anyway. "Too many chefs spoil the broth" as they say. And in any case, I also have my own goals in electronics. Even if I may never see them through.

    Where I'm living at right now, I can get semi-high speed internet easy and cheep, up to 12Mbps. This is great and all, but from a habitat perspective it's a terrible place to live. Awful people, no respect, drinking, drugs, violence, vandalism, theft. Nothing I want to be involved with and I can't do anything about it, so I need to move. The best prospective place for me to live at other than here is in bumfuk nowhere Montana, as I am basically guaranteed a job. I don't mind being in the middle of nowhere habitat wise, but I simply can't live with only dial up Internet. (Yes I am pathetic, and it's not even 50k, it's like ~25k at best). Now, the nearest real town has a technical college/university, and I'm told that people can get high speed internet near there. Problem is it's ~50 miles away, and I can't actually live in that town.

    So the (loose) plan is, (1) get/make some kind of bad ass two way repeater that I can have installed in town (don't know how THAT is going to work legally, prolly on a friend of a friends house or something :/). (2) Send the signal up to another repeater on a mountain peek (dubious practice at best), (3) send that signal over the ~50 miles to another mountain peek, (4) send that down to my house. Any point could be microwave link or WiFi if it's feasible.

    ..........You can laugh now. It's OK.

    Yeah, I don't see such things happening either. But then again you never know. I was thinking that If I could use just WiFi and common sat TV dish's that would be easiest to do technology wise. I know very little about working with radio. But I figured that over the counter WiFi would be much easier to break into and get legal. Also it's ready made for internet connections. But I suppose this could be a bad idea after all.

    The DIY ham microwave link is a great idea thought for this situation. Building three links is going to be hard no matter what. But the performance looks about right. At least the technology is sound. I would need a license, but that is the least of my worry's I think. I'm also going to have to get friends in the national forestry service to pull some strings to make it legal though. LOL. Maybe I can have it written off as "forest monitoring equipment". Yeah... that outta work. XD

    At this point, I'm open to all options. Though it deviates from the thread topic.
     
  11. Blakebalfour

    Blakebalfour New Member

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    I have a a old channel master dish it's probably 6 foot. But my question is how far could I reach non LOS. My parents get dsl but I don't (1.2 miles) the dish is at their house. Possible?
     
  12. chicowoodhill

    chicowoodhill New Member

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    Depends on a lot of factors. Through trees, buildings, or earth? Which frequency band? How high can you go to reach over obstructions?

    1.2 miles is easy with LOS using simple equipment and antennas. But if you're trying to go through a large hill, you won't have much luck. Using a big dish (ignoring possible legal issues for the moment) can improve a weak link but won't overcome inherent path blockages. You might consider a relay bridge located at a site that can be reached by both endpoints.
     
  13. Blakebalfour

    Blakebalfour New Member

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    This is my situation the ground elevation of the house with Internet is 1096, the hill I have to get over is 1115, and the house I want to send it to is at 1036 this is ground level both are 2 story houses. Also there are trees through the path. Distance between the two is 1.21 miles or 6400 feet. Have the channel master dish there but that's probably not going to work without Los. I have read about 900 MHz stuff. What do you recommend I do? ( trees on backside of hill and a little on crest of hill but its relatively clear.
     

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