Cantenna cans in NZ

Discussion in 'NZ Computing' started by Dogboy, Oct 30, 2006.

  1. Dogboy

    Dogboy Guest

    Ive been building a cantenna so my sister who lives 5 houses down on the
    other side of the road can access my internet. At the moment I am using
    an imitation pringles (Mr Chip or something) can.

    I have no problem with my laptop but my sisters Aluminum Powerbook is
    marginal at best. Some research has revealed that the pringles type can
    is not really ideal for a cantenna and I would like to replace it with
    something else.

    Using http://www.turnpoint.net/wireless/cantennahowto.html as a guide I
    am looking for a can at least 3" wide but no more than 3.5" and the
    longer the better. The less wide the can is the longer it needs to be,
    so a 3.5" can only need so be a bit over 6" high while a 3" can needs to
    be almost 12" high.

    Does anyone know what sort of products available in NZ I would be
    looking for to get suitable cans? A look around Pak'n'Save revealed very
    few suitable cans.

    What did other cantenna builders in NZ use?
     
    Dogboy, Oct 30, 2006
    #1
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  2. Dogboy

    NilEinne Guest

    I've never built a cantenna.

    But from a quick look at my cans I have some that are too wide, 10 cm
    in diameter but should be tall enough (11.6-12 cm). These are budget
    peach slices and some other brand black doris plums. I also have
    several that are 8.5 cm in diameter within your range but no where near
    tall enough at 11.5 cm. These are the kind you get from Asian groceries
    e.g. with bamboo shoots and various fruits.

    Would it work if you cut off the bottom and top of one can and stick it
    to another?

    I do have one that is 8.5 cm in diameter but taller, about 13.5 cm
    maybe. Didn't measure it because it's not something you can get as it
    was brought over from the US.

    I would suggest you check out Asian groceries and also when looking at
    Pak'n'Save remember to take a look at all sections, soups are usually
    seperate from other cans.
     
    NilEinne, Oct 30, 2006
    #2
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  3. Dogboy

    NilEinne Guest

    BTW, it's probably Mr Potato, from Malaysia...
     
    NilEinne, Oct 30, 2006
    #3
  4. Dogboy

    Craig Sutton Guest

    Go to a different supermarket you can buy pringles in NZ
     
    Craig Sutton, Oct 30, 2006
    #4
  5. Dogboy

    NilEinne Guest

    Sorry to post yet again but I looked more closely at the page. Altho
    not within the calculated specs, it does say this:

    "This is the fun part. You're looking for a can between about 3" and 3
    2/3" in diameter. The size doesn't have to be exact. I made a good
    antenna with a Nalley's "Big Chunk" Beef Stew can that was 3.87" in
    diameter. Others have reported good results with big 39oz. coffee cans
    that are 6" in diameter. The pringles can is really too small for good
    performance, however. Try to get as long a can as possible. The old
    fashioned fruit juice cans should work well."

    So it sounds like the fruit cans should work since they're about the
    same size as the Stew can. For coffee cans, try Milo cans. They're
    AFAIK about the same size.
     
    NilEinne, Oct 30, 2006
    #5
  6. In message <>,
    If you can't get one long enough, the next best thing would be to get two
    and tape them end-to-end.
     
    Lawrence D'Oliveiro, Oct 30, 2006
    #6
  7. Dogboy

    NilEinne Guest

    But why would a pringles can work better then same kind of can of a
    different brand (it's actually not quite the same, it's a bit wider but
    a bit shorter). Dogboy did say pringles supposedly don't work well
    anyway (which is why he's looking for different, wider cans)...
     
    NilEinne, Oct 30, 2006
    #7
  8. Dogboy

    NilEinne Guest

    Yeah that's what I was thinking. If he sticks two of the 8.5 cm
    diameter cans together he should end up with a 23 cm long can i.e. ~9
    inches longer then the 6.86 inches for the 3/4 Guide Wavelength
    according to that site he had. He could even try a single 10 cm can as
    well and see which one works better.
     
    NilEinne, Oct 30, 2006
    #8
  9. A cantenna is a pretty limited beast, but if you must persevere you could get
    any larger can and cut it down with tinsnips before soldering it together to
    get a can of the right dimensions.

    Whatever you use will probably work if you have a line-of-site path between the
    two antennae. If you don't it probably won't work no matter what antenna you use.

    Parabolic reflectors (sky dishes) can get out to many kilometres. A short
    cantenna would probably be quite a good feed for a dish.

    You might want to google "waveguide horn", "waveguide slot antenna", "2.4GHz
    Yagi" and permutations thereof.

    Keep your antenna feeder cable as short as possible. Extend the cat5 not the
    antenna cable.
     
    Mark Robinson, Oct 30, 2006
    #9
  10. Dogboy

    Boozel Guest

    Does any one have any idea what would recive wi-fi signal better. a 5ft
    antenna or a home made cantenna???
     
    Boozel, Oct 30, 2006
    #10
  11. Dogboy

    Rob Guest

    Check out the home brew kits in your local supermarket. 1.7kg cans about
    $10. Or plumbers supplies for aluminium downpipes (if they still make them)
    --
    Rob


    How would a car function if it were designed like a computer?
    Occasionally, executing a maneuver would cause your car to stop and fail
    and you would have to re-install the engine, and the airbag system would
    say, "Are you sure?" before going off. (Katie Hafner)
     
    Rob, Oct 30, 2006
    #11
  12. Dogboy

    ChrisOD Guest

    Or you could try a parabolic dish out of asian cookware.

    http://www.usbwifi.orcon.net.nz/
     
    ChrisOD, Oct 30, 2006
    #12
  13. Dogboy

    Stu Fleming Guest

    Chinese cookware is the way to go, apparently.

    Or, for around $200 you can build a proper waveguide, hook it up to a
    Linksys WRT54 and serve your entire neighbourhood :)
     
    Stu Fleming, Oct 30, 2006
    #13
  14. Dogboy

    Flintstone Guest


    Why not use a metal pasta/spaghetti can from somewhere like The Warehouse?
     
    Flintstone, Oct 30, 2006
    #14
  15. Dogboy

    Richard Guest

    More important then the diameter is that the inside has to not have any
    of the ripples in it that most cans from like baked beans etc have on
    it, and the flat bottom

    This rules out spaycans and drink cans, since the bottom is domed, and a
    hell of a lot of others. All the alum downpipe I have ever seen has had
    vertical creases in it to make it look pretty. I dont think that will be
    suitable but it may be worth a try if you can get some and close the
    back off.

    Also, if using channel 1 or 11 at either end of the band then re-do the
    calcs on the correct center freq - thats good for 1-2 dB more over the
    2.45 that most calcs use.
     
    Richard, Oct 31, 2006
    #15
  16. Dogboy

    Earl Grey Guest

    Here's a design using a rectangular extrusion
    http://nuke.freenet-antennas.com/modules.php?name=News&file=article&sid=13
     
    Earl Grey, Oct 31, 2006
    #16
  17. Dogboy

    Dogboy Guest


    Thanks for all the excellent ideas. I will look into them in the near
    future.

    I have had a play with asian cookware and those USB Wifi dongles but
    they aren't really suitable for this application, fun though.

    The current setup is: long ethernet cable from my DSL modem to my
    Wireless AP which is placed up on a stool in the front right room of my
    house, my cantenna is attached with a 30cm long pigtail to the AP and
    points out the window at my sisters room which is the front left room on
    the opposite side of the road about 5 houses down.

    Its almost line of sight, with just a window at my end (does a 30s era
    window block wifi much?) and another window (or normal house walls) at hers.

    I have been using the graphing features of netstumbler on my laptop to
    test things out and I personally don't have any trouble connecting but
    my sisters Powerbook and Airport is very finicky. Im not much of a Mac
    person so I dont know if this is normal behavior.

    Does anyone know anything in the Airport settings that might help?
     
    Dogboy, Oct 31, 2006
    #17
  18. Dogboy

    Roger_Nickel Guest

    I have seen a 1200 MHz amateur band antenna made from extruded aluminium
    tube, expensive but you might get an offcut. Critical dimensions are the
    length of the feed dipole and the separation of the feed from the closed
    end. The closed end of the can should be flat. Make it moveable with
    respect to the feed dipole and you will have a handy tuning mechanism. A
    30 degree flared horn at the open end of the waveguide section will
    increase antenna gain. Take a look at the wok antenna, the gain will be
    higher than the cantenna. You might also consider the biquad (bowtie)
    antenna as a compact, non-fussy and moderate gain possible solution.
     
    Roger_Nickel, Oct 31, 2006
    #18
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