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Thread: DIY Antenna Question!

  1. #1
    rockrabbit
    Guest

    DIY Antenna Question!

    Greetings,

    First off, I want to thank everybody here for the wealth of
    information. I went from being a wireless novice to, well, less of a
    novice in no time reading the posts here!

    The question I bring to you today is this, I have seen quite a few
    ingenius solutions for USB wifi sticks being used with the notorius
    "Chinese parabolic cookware".

    This got me to thinking, I have the Edimax EW-7318USg which has a SMA
    connected Rubber Ducky.

    Does it make sense, (as in not cause a problem) to aquire a parabolic
    cookware item, drill a small hole in the center, thread the SMA through
    and then connect the Rubber Ducky?

    I am lucky enough to be in a area that offers free WiFi, but signal
    strenght is questionable at best, just thought this might be a neat
    idea to try, just the run the concept past the experts first!

    Many thanks!

    RR


    --
    rockrabbit


    - Talk to my Machine



  2. #2
    Jeff Liebermann
    Guest

    Re: DIY Antenna Question!

    On Sun, 23 Mar 2008 15:25:07 GMT, rockrabbit
    <rockrabbit@nym.alias.net> wrote:

    >The question I bring to you today is this, I have seen quite a few
    >ingenius solutions for USB wifi sticks being used with the notorius
    >"Chinese parabolic cookware".


    Ahem... Salad bowl reflector. Very vegetarian:
    <http://802.11junk.com/jeffl/antennas/Salad-Dish/index.html>
    Just shove the USB stick into the plastic pipe. Slide it back and
    forth for maximum signal. Flat bottom stainless salad bowls available
    from Ace Hardware.

    >This got me to thinking, I have the Edimax EW-7318USg which has a SMA
    >connected Rubber Ducky.
    >
    >Does it make sense, (as in not cause a problem) to aquire a parabolic
    >cookware item, drill a small hole in the center, thread the SMA through
    >and then connect the Rubber Ducky?


    Difficult to tell. There are two types of rubber ducky antennas. The
    short 1/2 wave variety, and the same antenna with a 1/4 wave
    decoupling sleeve. The top part is a 1/4 wave driven element, with a
    1/4 coaxial sleeve forming a "coaxial sleeve" antenna and are the same
    for both types. This is the short one:
    <http://802.11junk.com/jeffl/antennas/coaxial/slides/coax-ant.html>
    The longer one has an additional brass sleeve at prevent the coax
    cable from radiating. Sorry no photo, as I haven't destroyed one yet.
    The decoupling sleeve won't benifit much from an extra ground plane.
    The shorter one probably will. However, the effect won't be huge in
    terms of increasing the gain. All it does it prevent some of the
    signal from radiating in odd and unwanted directions.

    >I am lucky enough to be in a area that offers free WiFi, but signal
    >strenght is questionable at best, just thought this might be a neat
    >idea to try, just the run the concept past the experts first!


    Methinks you would do better to abandon the rubber ducky, and build an
    antenna that has some gain, such as a patch, panel, biquad, dish,
    yagi, corner reflector, etc. I'm a big fan of the biquad mostly
    because they're very easy to build (if you can solder). My favorite
    instructions:
    <http://martybugs.net/wireless/biquad/>
    <http://www.vallstedt-networks.de/?Fotogalerien/quad2>
    <http://pe2er.nl/biquad/index.htm>

    --
    Jeff Liebermann jeffl@cruzio.com
    150 Felker St #D http://www.LearnByDestroying.com
    Santa Cruz CA 95060 http://802.11junk.com
    Skype: JeffLiebermann AE6KS 831-336-2558

  3. #3
    rockrabbit
    Guest

    Re: DIY Antenna Question!

    On 2008-03-23 12:14:32 -0400, Jeff Liebermann <jeffl@cruzio.com> said:
    >>

    >
    > Methinks you would do better to abandon the rubber ducky, and build an
    > antenna that has some gain, such as a patch, panel, biquad, dish,
    > yagi, corner reflector, etc. I'm a big fan of the biquad mostly
    > because they're very easy to build (if you can solder). My favorite
    > instructions:
    > <http://martybugs.net/wireless/biquad/>
    > <http://www.vallstedt-networks.de/?Fotogalerien/quad2>
    > <http://pe2er.nl/biquad/index.htm>



    Methinks you are a genius!

    BiQuad here i come!

    Thanks!

    --
    rockrabbit


    - Talk to my Machine



  4. #4
    seaweedsl
    Guest

    Re: DIY Antenna Question!

    Wouldn't a ez-12 or EZ-F work well too? No extra connectors to buy?

    http://www.freeantennas.com/projects...te2/index.html

    http://users.picknowl.com.au/~gloaming_agnet/ant2.html



    It would be interesting to see a comparision between the reflector and
    a bi-quad.


    Steve


  5. #5
    Jeff Liebermann
    Guest

    Re: DIY Antenna Question!

    On Sun, 23 Mar 2008 17:23:45 -0700 (PDT), seaweedsl
    <seaweedsteve@gmail.com> wrote:

    >It would be interesting to see a comparision between the reflector and
    >a bi-quad.


    About the same gain and beamwidth. Small diameter antennas (i.e. less
    than 2 wavelengths across) generally have the same capture area and
    therefore the same gain. It could be a corner reflector, dish, patch,
    biquad, or dipole array, it will have about 7-10dBi gain. The shapes
    have a much bigger effect on higher gain antennas.

    --
    # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
    # 831-336-2558 jeffl@comix.santa-cruz.ca.us
    # http://802.11junk.com jeffl@cruzio.com
    # http://www.LearnByDestroying.com AE6KS

  6. #6
    rockrabbit
    Guest

    Re: DIY Antenna Question!

    On 2008-03-23 12:14:32 -0400, Jeff Liebermann <jeffl@cruzio.com> said:
    >>

    >
    > Methinks you would do better to abandon the rubber ducky, and build an
    > antenna that has some gain, such as a patch, panel, biquad, dish,
    > yagi, corner reflector, etc. I'm a big fan of the biquad mostly
    > because they're very easy to build (if you can solder). My favorite
    > instructions:
    > <http://martybugs.net/wireless/biquad/>
    > <http://www.vallstedt-networks.de/?Fotogalerien/quad2>
    > <http://pe2er.nl/biquad/index.htm>



    So a quick question, now that I have this built, what is the best way
    to use it... by this I mean, the antenna has to point at the source, so
    how to I keep it vertical? The thought was to get two rubber coated
    metal clips to form a tripod type stand.

    make sense?

    ideas?

    thanks!

    --
    rockrabbit


    - Talk to my Machine



  7. #7
    Jeff Liebermann
    Guest

    Re: DIY Antenna Question!

    On Tue, 25 Mar 2008 03:57:48 GMT, rockrabbit
    <rockrabbit@nym.alias.net> wrote:

    >On 2008-03-23 12:14:32 -0400, Jeff Liebermann <jeffl@cruzio.com> said:
    >>>

    >>
    >> Methinks you would do better to abandon the rubber ducky, and build an
    >> antenna that has some gain, such as a patch, panel, biquad, dish,
    >> yagi, corner reflector, etc. I'm a big fan of the biquad mostly
    >> because they're very easy to build (if you can solder). My favorite
    >> instructions:
    >> <http://martybugs.net/wireless/biquad/>
    >> <http://www.vallstedt-networks.de/?Fotogalerien/quad2>
    >> <http://pe2er.nl/biquad/index.htm>


    >So a quick question, now that I have this built, what is the best way
    >to use it...


    Ummm.... plug, point, adjust, and play. Monitor the signal levels on
    your computer or use Netstumbler. Position the antenna for maximum
    signal.

    >by this I mean, the antenna has to point at the source, so
    >how to I keep it vertical? The thought was to get two rubber coated
    >metal clips to form a tripod type stand.


    Methinks you'll need something more solid than that. The coax is
    rather stiff. A real camera tripod will work. I stuffed a test
    antenna into an electrical box:
    <http://802.11junk.com/jeffl/antennas/biquad2/index.html>
    which caused it to detune somewhat lower in frequency. Others ended
    up inside kitchen plastic food storage boxes. The one on my bench is
    held in place by two window shelf "L" brackets. The one I installed
    on a neighbors roof is inside a glass bowl, with the coax cable shoved
    through a hole drilled into a 2x6 piece of scrap wood. I built an
    array inside a glass baking dish. User RTV for water proofing if
    mounted outside. Lots of photos on the web. The basic idea is to NOT
    put anything metallic in front of the antenna.

    >make sense?


    I like to make dollars, not cents.

    >ideas?


    Ideas are easy. Getting someone to fund them is more difficult.

    >thanks!


    --
    Jeff Liebermann jeffl@cruzio.com
    150 Felker St #D http://www.LearnByDestroying.com
    Santa Cruz CA 95060 http://802.11junk.com
    Skype: JeffLiebermann AE6KS 831-336-2558

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